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.)