gold RC10 rear swaybar howto w/ pics

[nerius]

The story of Matt Oliver’s RC10. Matt acquired an A-stamp Cadillac RC10 some years ago for about twenty five dollars. Being visually impaired and not having the experience of putting together and fixing RC10 cars like some of us older folk Matt didn’t do much with it. It sat on his shelf for a long time. The car was just a bare chassis with no electronics and no body or wing. When I first saw it recently it seemed to be mostly complete mechanically but was misconfigured in several obvious ways. The important pieces of the car were intact and were in great shape. Because I was a whiz with these cars in my youth I decided to take on this restoration project for my friend Matt. I grew up just around the corner from the Ranch Pit Shop in Del Mar, site of the first-ever off-road world championship in 1985.

In starting to take the car completely apart it became clear to me that the car was never assembled correctly and was barely driven. The car never had the chance to be a truly awesome RC10. It was also clear to me that the car had had at least one major crash that resulted in a broken ball stud being lodged in the rear bulkhead, in the optimal corner hole. (I have since managed to get that threaded remnant of hardened steel out without damaging the bulkhead in a significant way, by using a conical carbide Dremel grinding bit and a 3/64” HSS drill bit.) This was indeed the most poorly configured RC10 that I had ever worked on. There were details everywhere on the car that rubbed me the wrong way. For example, all four shock shafts had deep markings from being forcefully held by wire cutters on the sliding surface, relatively far away from the threaded end, to the point where it prevented smooth operation of the shocks. I have built and fixed several RC10s for friends and neighbors and this car tops the list of most poorly-configured. I also saw that it had great potential. For example, the underside of the chassis was barely scathed. I would compare the car I started with with a terribly mangled beautiful woman. It deserved to be configured correctly and had never been in such a state.

Well Matt’s RC10 has reached a state of near mechanical perfection.

(Continued in next post.)

[nerius]

The gearbox was one of the first things I took apart. I wanted to see how the most important part of the car looked inside. This would be similar to examining the heart of a patient if you’re a doctor. I verified that the car was indeed not an Edinger because it had only one spring clip for the gear shaft attachments. The outdrive shaft was held tight (or not so tight) by a nut and not by the Edinger-style spring clip. In this particular gearbox there were at least three major problems. The first two problems were that both of the shafts held onto the aluminum center plate were not secure. They were both wobbling around. The third problem was that the independent outdrive halves, which are supposed to have two ball bearings installed each for rigidity, only had the flanged outer bearing installed. The excessive slop in the gearbox, caused by loose gear shafts and caused by lack of rigidity in the part that gets a lot of torque, resulted in wear in the aluminum plate holes that hold the shafts in place and resulted in excessive wear in the two plastic idler gears. The idler gears were so badly chewed up that new ones had to be ordered, coming from the re-release Associated parts selection. To secure the outdrive shaft to the aluminum plate the nut was tightened with a substantial amount of torque after putting red thread lock onto the nut and threaded end of outdrive shaft. As for the idler shaft, instead of using the spring clip, a flat clip was used instead. The spring clip is nothing more than a flat e-clip that is bent in an arc. The particular e-clip is a 3/16” e-clip that can be found in U.S. hardware stores. I decided that more strength in the idler shaft would be had by fabricating a shim that would sit between the aluminum gearbox center plate and e-clip. Shaving off a few hundredths of a millimeter at a time I filed a shim to be just the correct thickness to provide a tight fit, anticipating that an even tighter fit would happen once glue was applied to the shaft flange on the other side of aluminum plate. Reaching this ideal thickness I then applied JB Weld to the shaft flange and re-installed the shim and e-clip. The assembly without glue was holding securely enough for all practical purposes but I decided that the addition of glue would make the assembly even more bulletproof. Heat is used to relieve both red Loctite and JB Weld epoxy. Not an excessive amount of heat is needed to de-bond these substances; there is no danger of melting the aluminum plate or steel shafts when reaching that temperature.

The inner non-flanged bearings were missing (as mentioned earlier) on the outdrive halves and were sourced. We made sure to use period-correct metal shielded bearings in all places where bearings were missing or needing replacement. The internal clip securing the ball bearings in place is a 3/8” internal housing ring that can be found at U.S. hardware stores. I assumed that removing the original housing ring was nearly impossible without damaging it, and instead of spending too much time assuming the contrary I decided to go with the assumption that I would be visiting the hardware store in order to find this part.

I didn’t take photos of the inside of the gearbox but it’s quite beautiful. The aluminum gearbox plate was sanded with 1500 grit sandpaper to restore it to looking brand new. The original felt seals were intact and in pristine condition on the original car and were re-used. The four long black steel #4-40 socket cap screws holding the gearbox together were put away and similar screws made from 7075 T6 aluminum were used, in plain aluminum finish. The metal gears (outdrive halves and spur shaft gears) had serious burrs on the edges, enough to cause damage to the brand new plastic idler gears. A lengthy period of time was spent de-burring these metal gears with a small file, at the outer edges of metal gears. This must have been a standard feature on all early RC10s, namely that in order to be able to sell such a cool toy for only two hundred bucks some shortcuts in machining processes had to be taken. Black thrust bearing grease was used on thrust bearing and clear diff lube was used on diff balls, in very small amounts of course. The original spur gear is in great shape. This isn’t the 48 pitch re-release spur gear. It’s the original large tooth gear. Finding a good pinion of the same pitch will be fun – luckily I have at least three in my drawers. Instead of using double-sided tape to dust-proof the bearing that is visible on left side of the gearbox (as per Edinger instruction manual), a semi-circular piece of very thin Lexan was cut out and glued on using Shoe Goo. A touch of Shoe Goo was also used to keep the white plastic left felt dust shield cover from falling out, even though it was already holding relatively snugly all by itself. The aluminum diff spring receptacle/plate had dents in the cylindrical section that receives the diff spring. I carefully bent the aluminum using a hard cylindrical object of slightly smaller diameter to restore the original shape. Finally, a #5-40 6061-T6 aluminum locknut with purple nylock material holds the diff assembly in place with a truly beautiful touch.

The outdrives are held onto the gearbox plate with button head screws (still steel on this car – but these screws can be removed without disassembling the gearbox). The instructions have you put a 1/16” thin nylon washer next to the button head screw, so that the nylon washer sits between the button head screw and the dog bone. Again, an appropriate nylon washer in the correct color was found at local hardware store. I compared the newly sourced nylon washer with originals that I had sitting around from thirty years ago and they’re very similar.

(Continued in next post.)

[nerius]

The rear wheel outers are vintage new old stock Pro-Line #2516 “nickle”. In removing flashing/burrs on these I realized that they seem to be metal-plated plastic. They’re slightly stiffer than stock plastic wheel outers. They weigh just a few feathers more too. We had to replace the wheel outers because one of the originals was badly mangled. These three piece rear wheels actually have a fourth piece – it’s a plastic shim that snaps onto the wheel outer pre-assembly. This is in addition to the plastic stiffener that you slip into the tire. In putting these wheels together correctly I realized that the tires are semi-pneumatic, which means that they’re air-tight but not inflated. I didn’t spend too much time analyzing how this works.

Since you’re probably wondering what the heck that rear swaybar is doing on an RC10 I thought I’d address that issue next. Recently I’ve developed a bit of a swaybar fetish and it has to do with being unable to get a single swaybar to work in my youth and finally figuring it out only very recently, after spending hundreds of dollars buying various parts with the hope that I would finally find a good and easy way to install a swaybar onto some of the more modern cars that I have in my growing RC car collection. My desire to install the rear RC10 swaybar has to do with two concrete observations. #1: box art on some of the early boxes shows an RC10 with what is clearly and undoubtedly a rear swaybar. (Side note: I am guessing that the car in photo on early boxes having rear swaybar is one of the original seven built after prototype, six of which went to nationals and the seventh of which was used to shoot photos for the early Edinger manual.)

#2: The rear bulkhead clearly has a groove in it, which is cradled by the fiberglass rear shock tower, groove being just wide enough to fit a nice 1.6 mm swaybar. Rear bulkhead clearly has screw holes in it which are clearly intended for buttoning down a rear swaybar using washers and/or flanged button head #4-40 screws, much like front swaybar is held down. Furthermore, the length of this groove matches the length of groove in front, namely it’s about 72 mm in length.

However, after examining, re-examining, researching, going online, searching, looking, investigating, inspecting photos found online, and so forth and so on, I did indeed come to the conclusion that the rear A-arms have no adequate mounting spot for a ball stud needed to have a swaybar. I did find photos online of rear A-arms that had a small hole drilled (this is where I got the idea for my mounting spot) but I did not find a single online source where a fully- and correctly-mounted rear swaybar for RC10 was depicted in photographs. This is one of the reasons I decided to write this essay – it’s because a lot of useful information that I now know has been gleaned from the internet – in order to reciprocate and encourage the idea that I believe in (which is to freely and openly share information that is correct and accurate) I am demonstrating my beliefs by publishing information that is correct and accurate, and that may be useful to someone such as myself trying to find information on how to properly mount a rear swaybar on an RC10, in the manner in which it was originally intended. By the way, the early Edinger manual does have instructions on how to mount a front swaybar. No mention is made of a rear swaybar. I got Matt’s permission to drill small holes in his vintage rear A-arms, carefully.

(Continued in next post.)

[nerius]

After doing a bit of research online I came to the conclusion that the original front swaybar parts for the RC10 are in fact repackaged DU-BRO parts. To prove this hypothesis I bought some vintage new old stock DU-BRO parts off the interwebs and compared them to what I had sitting in the drawer for thirty years. Sure enough, the parts are identical.

Here we have Cat. No. 181, Cat. No. 180, Cat. No. 188, and finally we have Sleepy-Pooh Cat. Kitty-Pooh is a bit camera shy.

The original Edinger manual instructions describe a very difficult step in the swaybar assembly process. This single step daunted me in my youth and prevented me from ever successfully installing a swaybar on an RC10 up until now. The step in question describes the soldering of the hex ball end (Cat. No. 180 in photo) onto the end of a piano wire, typically 1.2 mm or so in diameter. Furthermore, the inside of the hex ball end has a hole threaded for a #4-40 screw, going in about 3 or 4 millimeters deep. The Edinger instructions recommend to use acid core solder and/or acid flux for the soldering operation.

I have no experience soldering using acid core solder but I consider myself to be an expert in soldering and repairing electronics for hobby use. I felt undaunted by the task at hand, which was to fabricate front and rear swaybars for the RC10, using original DU-BRO ball ends and ball cups, in order to accomplish period correctness.

I considered using modern swaybar hardware but decided against it for several reasons. First, the point of this RC10 restoration was to restore the car to be close to period correct at least in the shape of parts, unless serious design flaws in original parts were encountered or if original parts were very difficult or expensive to source. Second, having already conquered the task of installing swaybars onto several cars using ideal modern parts that I’ve come across, doing the same on this car would just be a walk in the park. It would not be a big challenge. Third and most important, the original front swaybar for the RC10 consisted of a threaded ball stud that screws into the front of the front A-arms. The A-arms have a small hole just next to the 2.8 mm hole that houses the front shock mount shaft. This smaller hole is under 2 mm in diameter and is meant for a #2-56 threaded screw/stud. I wanted to use this original hole instead of making a new one and/or instead of expanding the existing hole in size. Modern ball studs on modern cars of comparable size typically have ball studs with an M3x0.5 thread or a #4-40 thread. That’s an order of magnitude larger than a #2-56 thread. Furthermore, the original DU-BRO swaybar ball links used in original RC10 have a ball interface that is 3.90 – 3.95 mm in diameter, whereas the smallest variant of ball studs used in similar-sized cars today have the balls at 4.3 mm diameter, sometimes even 4.8 – 4.9 mm diameter. (Note: other non-swaybar ball studs on the RC10 have the standard 4.3 mm diameter.) The smaller balls used in a part as dainty as a swaybar and not requiring excessive strength seemed like an elegant choice. Because we would be drilling a hole in the rear A-arms for a swaybar ball link, a small diameter hole for a #2-56 screw seemed like a less intrusive modification than a larger diameter hole for a #4-40 screw.

After carefully making the holes in the rear A-arms and noting how perfectly symmetrical they were I originally mounted the DU-BRO #2-56 ball studs (Cat. No. 181) pointing back, meaning the ball was protruding to the rear of the car. I don’t have photos of that setup.

I heated up my 40 watt soldering iron and felt undaunted by the task at hand, which was to solder DU-BRO hex ball ends, internally threaded for #4-40 screw, onto a hand-bent 1.6 mm diameter piano wire purchased from local hobby store. 1.6 mm was chosen for the rear because it fits neatly into the groove intended for this purpose – a smaller diameter wire would not have fit as snugly. Furthermore, while 1.6 mm seems like a thick wire to use for a swaybar, my reasoning for this decision is as follows. I will explain this decision by asking a rhetorical question. If I were designing a beautiful woman and if I wanted this beautiful woman to have feminine attributes that clearly identified her as being a truly beautiful woman, would I exaggerate those attributes in order to eliminate the possibility of doubt as to her being a beautiful woman? Likewise, since I’ve been starved of having the ability of successfully installing a swaybar on an RC car in my youth, I wanted to exaggerate the swaybar’s ability and function now that I have the ability to install one properly. 1.4 mm diameter piano wire was chosen for the front, which fits snugly into the front groove.

(Continued in next post.)

[nerius]

My original rear swaybar attempt is pictured next to the car.

As you can see the length of wire between ball end and bend on each side is longer on the standalone swaybar. This is to account for the extra reach needed to achieve a “right angle fit” when the ball stud mounted on the rear A-arm is pointing towards the rear. Using my physics knowledge gained from a very knowledgeable and talented high school physics teacher I concluded that, all else such as wire thickness being equal, the swaybar mounted on car currently (with balls pointing forward) is stiffer. The stiffness of the swaybar is partially due to the total angle by which the bar in the middle has to bend or rotate. Because the translation distance of the ball stud on A-arm during suspension travel is equal whether it sits pointing forwards or backwards, the shorter side lengths of the current swaybar result in a greater arc of rotation in the bar when one wheel is fully up and other is fully down. Furthermore, the mechanical advantage in torquing the bar is greater when the sides of the bar are longer (put another way – the bar exerts more force at the ball ends if the sides are short, assuming torque on bar is the same). In other words, if you want to soften the rear swaybar you can either choose a thinner wire material or you can use the same gauge wire but lengthen the side pieces between bend and ball end on piano wire.

My first attempt at soldering the original rear swaybar took a long time but resulted in a fairly nice swaybar. The hardest part was getting the ball on the rod straight. I had to use many tries before finally getting it straight. I imagined myself soldering a 14 gauge wire onto a 3.5 mm bullet connector. The same challenge exists there – namely to get the bullet connector to sit straight on the wire. Then, there was solder residue on the ball end. It didn’t look professional. I tried to wipe as much of it off as I could with the soldering iron without melting the current position the ball was in. Finally I took a file and made the six sides of the hexagon smooth again. Unfortunately on my original bar I took off quite a bit of the black coating that was on the ball end with the file. So the balls look silver both because solder got onto them and because the black coating was partially filed away.

At some point of the soldering process I smelled what seemed to be CA glue vapors. I recalled that I tried gluing a swaybar together in my youth after failing to solder it. I was using some of these thirty year old ball ends that had been sitting in the drawer. I continued pouring and boiling flux into the ball end hole and I continued melting solder into this hole until I could smell no more of these vapors.

The second rear swaybar was more of a success as was the front swaybar. But again I faced the same problems: getting the hex ball ends on straight and finishing them to look professional. I think that a little bit of solder on the ball ends and taking a little bit of black coating off is as good as it gets, and is expected on these cars from the 80s.

The rear bulkhead clearly has a groove made for accepting a swaybar. The notches at the edges of this groove even match the style and nature of the notches at the edges of the grooves found in the front suspension mounts, which are intended for exactly that purpose, namely to delicately cradle a swaybar.

The front swaybar cups (the clear plastic DU-BRO parts) were cut to be shorter using a Dremel tool. In photo you can see them bottoming out against each other, meaning that this turnbuckle link cannot be shortened any further. My original approach was to shorten the cups before even trying the original length of ball cup. This hunch proved to be correct. Right now the length of the link is close to optimal when examining the front swaybar angles as the suspension moves. With the original plastic cup length the link would have been about 1 cm longer than now.

One of the photos shows front swaybar instructions found in original Edinger manual. No mention of rear swaybar is made.

The threaded connecting rod used between plastic swaybar ball cups is #2-56 connecting rod, also called threaded stud. It’s made of aluminum and isn’t exceptionally strong. I assume that it’s 6061-T6. It’s strong enough for its purpose – these swaybar parts don’t get a lot of stress (unless there’s a collision with another car or unless there is the act of hitting something stationary, resulting in direct impact to the part). The aluminum connecting rods can be ordered from a supplier such as McMaster-Carr. A 7075-T6 or titanium grade 5 connecting rod would have been more ideal but was not found. I’ve had a hard time finding even strong steel threaded rod in these small sizes.

(Continued in next post.)

[nerius]

The car came with white plastic “star nuts” for attaching the wheels. These aren’t the two-prong white plastic through-hole wing nuts that I had on my RC10 way back in the day. These are three-prong nuts having no through-hole. They’re quite interesting. They are very delicate. I don’t want to wear the plastic in its ability to hold the wheel in place. Therefore I’m using these as little as possible. They’re on the car with the wheels off but with the wheels on I’m using an aluminum 5-40 locknut up front and for the rear I’m using the 8-32 white nylon nuts that came off the original steering blocks.

Almost every screw in the car has been swapped from black-on-the-outside steel alloy to black anodized 7075-T6 aluminum, made by fastener-express.com. I visited fastener-express.com in person at their Orange County factory and saw how they make their screws. I was pretty impressed. Their smalls-sized screws are aged to T6 after the screw is formed out of 7075. I have been reading about various materials online and here is my summary of what I know. 7075 was secretly invented by Japanese more than half a century ago. It’s about twice as strong as 6061 and weighs about the same. 7075-T6 is approaching the strength of titanium grade 5 in its tensile strength. The only aluminum alloy that claims to be clearly stronger than 7075 is this new stuff called 7068, which hasn’t hit widespread use yet.

There are eight screws on the car that I’d consider reverting back to black steel alloy. These are the eight highly structural #4-40 screws that hold various pieces of the chassis together – four screws on the front nosehead tubes, two side screws into the rear bulkhead, and two screws into the rear of the gold anodized aluminum transmission cover.

A total of six titanium #4-40 3/4” length socket cap screws are used in the suspension mounts – four screws in the rear, for both top and bottom of shock, and two screws in front for the top of shock. These titanium screws used are Racers Edge part #069. They’d better be made of titanium grade 5 alloy and not of grade 2. Making a titanium screw this small out of grade 2 would be quite a mistake for strength reasons. There is no mention on package of exact material used, only “titanium”.

When building up the rear shock standoff (top of shock), I followed Edinger instructions and put the white flanged bushing on with flange facing forwards. Edinger instructions tell you to put an aluminum washer between the back nut and white bushing, but I suspected that the aluminum washer has a sloppy hole and that it might touch the shock cap, being of a sufficiently large diameter. I found some 1/32” thick black nylon washers that came from a B4 front-end, that not only are smaller in outer diameter but also fit more snugly onto a #4-40 screw. I’m using a thin steel zinc-plated #3 washer on the socket head side of the 3/4” screw, reason being that it increases the surface area of stress on fiberglass when shocks are impacted. With the exception of what I think is one tiny nut in tranny shell and one large nut to hold down the outdrive gear shaft, all nuts are 6061-T6 alloy, ordered from fastener-express.com. They don’t make their own nuts but sell them in order to better cater to customers looking for a complete fastener solution. Even the tiny #2-56 nuts holding the backside of the rear A-arm swaybar link ball studs are aluminum locknuts.

(Continued in next post.)

[nerius]

Here is one peculiarity that has baffled me for thirty years. The rear shocks on the RC10 are angled forwards whereas the A-arms are angled backwards.

I think I finally discovered a reason for what seems to be this misalignment between rear shock angle and rear A-arm angle (squat). (It would seem natural for the shock to be mounted on the rear A-arm at exactly a right angle to the A-arm squat angle.) The literature (manual) or box advertising (I can’t remember which) mentions that the RC10 has an adjustable wheelbase. Sure enough, the rear suspension mounts have extra holes made for shortening the wheelbase. The forward/backward dogbone angle on the stock RC10 also leaves a symmetry for shortening the wheelbase. It seems, based on rough estimations, that shortening the wheelbase by using the alternate rear suspension block mount holes would place the shocks at a more optimum angle, or perhaps even alter the shock angle too much and place the shocks at an acute angle with respect to the rear A-arm squat angle. However, the rear bulkhead prevents us from using the shortened wheelbase, unless the rear bulkhead or the rear suspension mounts are physically altered. The front edge of the rear suspension mount already practically touches the rear bulkhead, preventing such a configuration. My guess is that the rear shock angle is a remnant from the original design which was to place the rear suspension mounts slightly more forward. My guess is that Associated lengthened the wheelbase after the prototype was made and that they added the wheelbase adjustment claim to the literature, not being aware of the full situation.

Another quirky fact is that in the early Edinger manual the photos for the rear shock standoffs (top of shock) show the white flanged bushing with flange to the rear, placing the top of the rear shock further forward. Yet, in the text to the very same manual instruction step the printed instructions tell you to disregard photo and flip the plastic white flanged bushing the other way around, placing the top of rear shock more towards the rear.

In any case, the slight angle misalignment of the rear shock with respect to A-arm arc of travel (squat angle) is not a big deal. The rear suspension still seems to be very effective for an early car. I experimented with putting a nylon spacer-bushing at the bottom of rear shock mount surrounded by strong steel washers as a way of getting the bottom of the rear shock more forward, but that design leads to too much flex in an already flexible rear A-arm (flexible by today’s standards of slightly improved materials).

(Continued in next post.)

[nerius]

Here is a photo of non-swaybar linkages.

Before we discuss linkages I want to point you to the axle spacer-shim on the front axle. One of the goals of this restoration was to eliminate all play/slop in the front and rear wheels. The front wheels had a significant amount of side-to-side play on the axle. This is expected as play is practically required to eliminate side load on the front bearings when the car is going straight. However, I find that there is a way of eliminating this play without creating side load on the bearing by introducing a very small amount of preload in the bearings through use of a shim that only touches the inner race. One way to do this is by machining a shim of exact thickness but a far easier method is using a shim that’s slightly too thick and using a very tight-fitting locknut. You tighten the wheel locknut until the wheel is definitely too tight (not spinning for one minute if you spin it by hand). You then back the nut off gradually until the front wheel gets to the state of spinning as freely as it would without the shim. This potentially introduces a very small amount of side preload in the bearing but it eliminates side-to-side slop with respect to the front wheel bearings and bearing axle.

Back on the subject of linkages. The original hardened steel ball studs on the RC10 are #4-40 threaded and have a ball of diameter that ranges between 4.28 and 4.30 mm, as measured on various samples at my disposal. 4.3 mm is considered to be a standard size of ball stud today. The original white ball cups and all ball cups tested for this size of ball have a noticeable amount of play when mounted on the original RC10 ball stud. It’s not much play – perhaps only a few hundredths of a millimeter of free travel. However, with so many ball linkages the slop quickly adds up. The servo already has a bit of play in its internal gears. Between the servo and steering blocks there are 2 joints. The first steering block itself might have a bit of play around its axle. The linkage heading to right wheel passes through 2 more ball linkages to arrive at the right steering block, which might again have some play around its axle. The right steering linkage then heads out to the right steering turnbuckle which again has 2 more ball swivels. So that’s a total of 6 ball joints/swivels between servo and right wheel knuckle. This does not even account for slop in the hinge pins or wheel bearings. It’s a lot of slop if things aren’t tight.

In investigating possibilities of how to eliminate front-end slop, various ball studs were measured using a precise caliper. It was found that Lunsford #4-40 threaded ball studs (I don’t know if they still make them) have a ball diameter that varies between 4.33 and 4.35 mm, which is just enough of an increase in size to eliminate the slop in ball joints, for the most part. Furthermore, it was found that Team Associated part #31305, “Turnbuckle Eyelet”, is a very tight-fitting ball “cup” with an open end, meaning that it’s not a full cup, but rather has two open sides. It was decided to replace all ball studs and all ball cups with these. One advantage of the turnbuckle eyelet over the closed-end ball cup is that you can make a finer adjustment to the turnbuckle if you have the open-ended ball eyelet. You can make a 180 degree rotation instead of a full 360 degree rotation as an incremental step in adjusting turnbuckle length.

The exact Lunsford titanium ball studs used are part #7106 for the rear bulkhead and various combinations of #7108 “medium” and #7107 “short” for the rest of the car, in intelligent combinations. #4-40 connecting rods between eyelets are old-style threaded rod cut to length, meaning that they are not turnbuckle-type with adjustability while turnbuckle is attached to car. This is in line with how the way things were back in the day. The #4-40 threaded studs used are made of aluminum, which is probably a 6061-T6 alloy that is definitely not as strong as titanium grade 5. The material does not seem to be as strong as 7075-T6. They are exceptionally lightweight however, weighing what seems to be as much as a feather. A 1.5” length can be bent/deformed by hand if a great amount of force is applied. This is not the material of choice for a turnbuckle in a racing situation where direct impacts with other vehicles are common. I have been and am trying to obtain/machine titanium grade 5 threaded rod in #4-40 pattern but am encountering hurdles. Having #2-56 threaded rod of this material would be nice for the swaybar linkages as well. Cutting a long piece of threaded rod to an exact length and beveling the ends is simple and not too time-consuming using a Dremel tool. All that is needed is long lengths of titanium grade 5 threaded rod.

(Continued in next post.)

[nerius]

All ten 1/8” diameter suspension hinge pins are made of titanium grade 5 alloy and were machined by me on a lathe. The diameters are about two hundredths of a millimeter thicker than the standard 1/8” which provides a tighter fit on older cars with sloppy and worn out suspensions. The surface of the hinge pins was ground with a 1500 grit sandpaper for smooth rotation in suspension. The notches in hinge pins have a slightly tighter 0.5 mm or so width and as a result the suspension hinge pin e-clips fit more securely (diameter for e-clip seating being the same).

The conical washer used on the outside of the rear axle next to roll pin is Associated part #6388. Four come in each package. I think that the instructions tell you to use just one per side, leaving enough in one package for two cars. Well, I used two packages. I’m using four conical washers per side, oriented in the same direction. This left a tiny bit of play in the rear axle bearings as a result. Furthermore, four conical washers offer more strength in extreme cornering with extreme side forces being put on the rear axle. Four won’t crush as easily as one. Thin conical washers are springy in nature and I don’t want them to compress and/or deform while the vehicle is being used. Stacked together they can be used as shims. Note to self: try using angular contact bearings on larger cars.

You can see the titanium machining on the ends of the hinge pins in both photos above. The steering knuckle hinge pin has black nylon washers above and below caster block. This is the way the original was designed (although they used white instead of black spacers). I left the lengths and distances between e-clips as original as possible on the revised hinge pins.

The way that the front structural tubes are attached to the chassis makes me cringe a little bit, especially considering that these screws used by me aren’t made of steel (they’re 7075-T6). There seem to be angles involved and the chassis material seems to demand to be bent to get a tight fit. I inserted nylon washers, black in photo, in front of and behind the front chassis nose plate, in order to provide a little bit of “crush cushion” because the tightening of these screws became a bit uncomfortable. It was probably a mistake not to use the original steel alloy screws (readily available at any U.S. hardware store) in this particular spot. However, the aluminum screws are holding well and don’t seem to be close to breaking or close to severe distortion. What happens in an impact is a different matter however.

The shocks, front and rear, were completely overhauled, including the bottom seal. The only part not re-used was the internal housing ring that holds the red o-rings and such in place at the bottom of the shock body. Again, I assumed that by taking these off it’s not possible to not bend them such that they become deformed. A hardware store in the U.S. will typically sell 5/16” internal housing rings, which is exactly the part I’m using for this clamp. They’re one size smaller than the internal housing rings used to hold the ball bearings in place in the gearbox outdrive halves. They match the original parts that came in the Associated kits.

To seal the shocks caps I’m using 1 mm thick black o-rings also purchased from the hardware store. This o-ring seal was apparently an “upgrade” back in the day. The original fiberglass-like seals are still in great shape, and have been put away in a small ziplock bag. It’s amazing how many RC10 parts this hardware store has! They even have the exact rear axle roll pin I’m looking for! The o-ring for sealing the shock cap to shock body should be chosen such that it’s the smallest diameter o-ring that still fits reasonably over the shock body after being stretched on. 1 mm for the o-ring thickness seems to be the perfect thickness and is the thinnest the hardware store had. I found out that sealing shocks with an o-ring is very unforgiving and will make that seal bombproof. I tried forcefully pushing a sealed shock all the way in when not enough “bleeding” had been done, and guess what… the bottom seals busted out. In other words, hydraulic mechanical advantage can be a very powerful tool. The force from the compression of shock oil caused the bottom seals to start rupturing, while the shock cap exhibited zero oil leakage. Long story short… don’t force the shock piston in when you seal the shock with an o-ring! Bleed the shock with shock cap loose first! I managed to repair the seals on the busted out shock. No permanent damage occurred.

I’m also using a black o-ring at the bottom of the shock, between bottom spring cup and shock body, inserted on shock shaft on the outside of shock, visible in some of the photos. These can be cut off with a razor blade without any disassembly if they prove to be useless. The reason for these is that I wanted them to touch the bottom of the shock body at the same time that the shock shaft hits the shock cap internally, when the shocks “bottom out”. I noticed that inside the shock cap there is a cylindrical surface machined specifically for allowing the shock shaft to hit when the shock shaft is fully in. You might hear a metallic “smack”, especially in the rear shocks, when the suspension bottoms out. The o-ring is meant to touch the bottom of shock body just slightly before the shock shaft bottoms out, to cushion the shock smacking just a bit. It also presses in on the bottom seals, which may or may not be a good idea. It may help to press in on the bottom seals once in a while to make sure everything there isn’t “popping out”, kind of like what happened when I erroneously forced the shock shaft all the way in before the shock had been bled properly. I made sure that not much pressure is applied by the o-ring in this spot before the shock shaft hits the shock cap. This is only an issue in the rear currently because on the front suspension the A-arms hit the fiberglass shock tower before the shock has a chance to bottom out. Black cushioner o-rings are present on all four shocks however.

(Continued in next post.)

[nerius]

The steering blocks were found on eBay and purchased for a relatively small amount. I don’t remember if the claim was that they were made by MIP, a very coveted maker of RC10 hop-up parts. (On my list of aspirations is to acquire a 4WD kit made by MIP for the early RC10.) The steering blocks are designed beautifully. Instead of using two #8-32 7/8” flat head screws in this location you replace them with screws of only length 9 mm or so. The kit comes with two shoulder bolts that are actually a cross between a shoulder bolt and a standoff. They screw onto the chassis through-screws from the top and provide a very precise 1/4” diameter cylindrical surface for ball bearings. The same size flanged ball bearings as what is used on the rear axles are used here. The original shallow white nylon nuts that came with this kit had one side of nut with a cylindrical offset that matched the inner race of ball bearing well, not really touching the outer race. However, there was a bit of slop/play on the shaft – the bearings were free to travel about 0.5 mm up and down the shaft. Having run out of conical washers used on the rear axles I employed carefully chosen black o-rings to provide a slight amount of bearing preload. The o-rings are only touching the inner race and not the outer race. Aluminum nuts secure the assemblies from the top. The nylock material on these nuts is particularly tough – the nuts won’t come undone by themselves. The pressure of the nuts onto the o-rings is carefully calibrated to allow a relatively resistance-free rotation of the steering blocks. Best of all there is no perceptible play in the steering blocks. The center linkage consists of DU-BRO #4-40 ball swivels, with conical washer not needed and not installed. This is DU-BRO part #2161, in black. The ends of the black plastic eyelets were cut about 2 mm to allow them to butt up against each other just as this connecting tie rod reached the ideal length.

The aluminum wing tubes on original car were battered in with a hammer and were severely mushroomed at the ends. It was not a pretty sight. I took them out and reshaped them. I made sure not to remove more than 0.5 mm of length from the overall length of tube, and I made sure to leave them at exactly equal lengths. The end that was battered was ground to a flat surface again and beveled at a 45 degree angle just a touch. A very shallow taper was added to the last 2 mm of tubes to allow the tubes to fit better into the rear bulkhead holes. The healthy end, now sticking up and previously inside the bulkhead, was also made to have a flat, smooth finish at the end and a very minuscule 45 degree bevel was added just to make them look extra nice. Even if you took the tubes out of the bulkhead and examined them there would be no trace that they were once battered in with a hammer. I got them in carefully by having some soft wood between hammer and end of tube. The wood will deform much sooner than the aluminum will. They’re in as far as they will go. They are bottomed out in the holes in the rear bulkhead. They’re sticking out equally, as measured with a caliper. We’ll find out how well they’re positioned when it’s time to mount the body.

(Continued in next post.)

[nerius]

Another peculiarity that the RC10 has is that the rear shocks are incredibly long. Uncompressed the rear shocks are way longer than what can fit on the rear suspension. The rear suspension mounts and rear A-arms are such that the plastic on them prevents the A-arms from rotating too far downwards. However, over time, these plastic stops on the parts wear down and the rear arms start extending further and further down, causing all sorts of problems in the dogbones and drive train. A common technique was to place limiters into the rear shocks, internally, to limit the extension of the shock. Without limiters the shocks would have to be manually pressed in by almost an inch just to mount them onto fully extended rear A-arms. When I took the rear shocks apart I did indeed find limiters inside, made of a rubber tube material. I manufactured limiters made from a very thin brass or copper tube, with plastic bushings on the end that touches the shock body for stress relief and to allow fine tuning of ride height without replacement of manufactured tube. A thin tube for this purpose is better than a volume-displacing rubber tube because the thin metal tube allows more oil volume inside the shock body. The current ride height adjustment places the rear equal to or just a hair above the front at full extension, it seems from close inspection. The front shocks are not being limited. The rear ride height is being limited before the plastic on suspension parts bottoms out. In other words, the ride height could be raised slightly in the rear, by about 5 mm – the plastic parts would allow it.

Original vintage chassis screws are used on the car. These are aluminum Phillips flat head 100 degree #8-32 screws, most of which are 1/2” in length. They are light green in color, presumably because they’re anodized such. In trying to install absolutely fresh screws I obtained Associated parts #3324 and #6280. Both are a dark green screw of the correct size. They’re not light green and don’t look period-correct. So, the original slightly worn-out screws were re-used. One avenue I’d pursue is the purchasing of this screw in blue anodized color from fastener-express.com. I believe that this screw is made by them in-house and is of 2024-T4 aluminum, which is quite strong and unquestionably strong enough for a #8-32 RC10 chassis screw. I would use a slightly shorter screw in six spots – on two of the front suspension mount screws on each side (total of four screws) and on the rear hole on the rear suspension mount on each side. With the standard 1/2” screw these poke out a bit too far – by about 1/8”. It seems that a screw of length 3/8” would fit flush with the edge of the plastic in these six spots. I would also use a #8-32 button head screw and not a flat head screw for the rear body mount. I would make that one size longer than 1/2” (perhaps 5/8”, and grinding down length if necessary) in order to grab the body mount better, which was never a really secure fit, perhaps by deliberate design. I would especially make the body mount screws longer (both front and rear) if using the aluminum spacer-washers under the white plastic body mounts.

(Continued in next post.)

[nerius]

Here are some parts that we didn’t use.

The original white steering blocks that slip onto the #8-32 7/8” long chassis screws don’t seem up to the task of creating a truly awesome RC10 of near period correctness. The MIP-style ball bearing steering blocks are way more awesome.

The original front suspension mounts have a significant amount of play in the hinge pin hole. They are too loose and too worn, or too damaged by impact. Black ones made of a revised material provide a very tight fit and seem much tougher. Small tubes made of nonporous alumina ceramic having an inner diameter of a very precise 1/8” were machined. This is an extremely hard material. These inserts could be used to “repair” the front suspension mounts so that they don’t have that play anymore. This would involve altering the original part, by drilling it out and by inserting the alumina ceramic inserts. You want to have the hinge pin rotating in the A-arm and not in the suspension mount, by the way. With this very hard material it’s difficult to insert a tightly-fitting hinge pin without marring its metallic surface (e.g. titanium grade 5), unless glue is used.

In photo you’ll see a shock collar (or “spring preload tensioner”) from a Yokomo-era car. I have three of these but not a fourth. These have a grub screw which digs into a shock body. They look super cool and work well but they put a mark into the shock body.

Original ball studs are not used anywhere. Their ball diameter is 4.3 mm or less and they don’t provide a tight enough fit for our purposes. In trying to show off a beautifully designed car it would not be appropriate to use sloppy linkage.

Associated part #8830 is a very well-made and well-designed sway bar ball mount with a very nice through-hole (for piano wire) and set screw tightening mechanism. The material is a hard aluminum. The ball is 4.3 mm in diameter, or of that general size. It’s a great choice for swaybars but is not period correct. It does not offer the challenge of manufacturing a period-correct swaybar and its ball diameter is larger than the 3.9 mm we’re using for our swaybars.

The two plastic low-profile nuts came with the ball bearing MIP-style steering block kit. I am using aluminum nylock nuts instead for a more precise and secure adjustment capability.

Original turnbuckles and white RPM ball cups are in photo. Both of these have too much play (when put on original ball studs) for our purposes. Perhaps one or the other could work with the slightly larger Lunsford balls. The open eyelets being used currently provide a 180 degree adjustment increment instead of the usual 360 degree adjustment increment you have with ball cups.

Original battery tray from one of my original cars is also pictured. I can’t get the yellow off by using various test chemicals. The yellow color does not match the white parts on Matt’s car. It’s yellow from age and cruft. We’re trying to mount the battery lengthwise in the car, by using only one battery cup as was done in original one-off RC10 prototype, hand made by Curtis Husting. A quirk that many of us have experienced is that all of the early chassis have holes drilled slightly off to one side for this single battery cup mounting position, and these stock holes are lacking the countersink on under side for a flat head screw.

(The end.)

[nerius]

Some photos of the finished product.

[nerius]

Last photos.

[gainsy]

Looking good there fella
Always good to see a nice rc10 brought back to life
Not sure i would have mounted the esc switch where you have put it but back in the day that was quite normal so understand why you have stuck it there

[nerius]

Thanks!
As to the switch, I don't recall every seeing it mounted there. My pet peeve is having to remove the body to turn the car on and off. And I do realize that it's probably better to have the car battery unplugged when the car is not in use. I weighed the options and decided to go with the least intrusive approach - meaning I didn't want to cut extra holes in the body nor did I want to make any other sort of irreversible change to the car. That mounting spot is the only reasonable spot I could come up with that satisfied my criteria. I thought I was being inventive and original! Lol.