Procat belt slip.

[tahustvedt]

Is there a trick to eliminate belt slip without excessively tightening it? I have the stock pulleys front and rear and a new 4,5mm MXL belt. I loosened the front diff so that when I hold the front wheels and try to swing the car up the diff gives before the belt slips, but the belt still slips often while driving. It also sits off to one side of the front pulley and won't go to the center. I bought a used MMS (I think) front diff which will at least help with the centering, but I suspect it's slipping in the rear as there's less wrap around there. I guess I'll find out when I get the new front diff. Maybe the rear diff is worn, though it didn't look like it was when I had it apart some time ago. I want to avoid a slipper clutch.

If I can't get it to work and want to keep driving it I might mill new diffs for GT2 3mmm belts out of Delrin.

[Peakey]

What electrics are you using? If it's brushless then I think your going to have to find a slipper. If not take a look at Luke's thread here: http://oople.com/forums/showthread.php?t=48668&page=23

It's a really handy I keep going over bits now and then.

But if you do need a slipper robin c on here has had a couple of bosscat ones made I'm sure if you ask him he'll be able to get you one done.

[Danf1275]

After I fitted an MMS front diff in mine, any slip issues were found to be belts from layshaft to back diff. Belt to front is now relatively loose.

As far as I can remember, all belts are still original, with mild 9t Ezrun brushless.

[tahustvedt]

It's brushless and hot. :P 6000 kv. Maybe I can limit the torque on the ESC somehow.

I'll check again that it's not the belts between the layshaft to back diff.

[tahustvedt]

Hmm. It might be the rear belts after all. I replaced them a while back and they might be one tooth too large (vague memory). The adjustment cups are at the tightest position. Guess I should order some new belts from SDP-SI before I condemn the center drive.

[Danf1275]

If you remove top 2 screws on each side of the rear gearbox, you can 'peel' plastic housing back to assess belt tension in situ.

[Peakey]

Originally Posted by tahustvedt

Hmm. It might be the rear belts after all. I replaced them a while back and they might be one tooth too large (vague memory). The adjustment cups are at the tightest position. Guess I should order some new belts from SDP-SI before I condemn the center drive.

If you pm Nigel Npdp72 on here he sells standard size belts that look great, I've not used mine yet but are a direct replacement for the Schumacher ones.

[tahustvedt]

I inserted some rubber between the pinion and spur and lifted the car by twisting the rear wheels, and then jerked. It crackled. I'm using homemade aluminum eccentric cups and didn't make them eccentric enough so max tension isn't enough. I checked my order with SDP-SI and I did buy the right ones. 6mm wide, 72 teeth and MXL.

Guess I should have made some new ones, but I found some plastic ones on Ebay for £3 so I just bought them instead. :P

[tahustvedt]

Do you guys ever experience front belt slip at all? What if you land on the front wheels with throttle, for example?

[Adam F]

My xls suffered badly from front slip, even with a slipper clutch and new belts..

That was with an 8.5 motor..

Would be interested if you find a fix or mill some parts that use a more durable belt..

[Peakey]

As of yet I've not had a problem but I'm using a 6mm main drive belt and some high toque rear belts. I tensioned all mine up and then locked the front diff housing down with 8 screws.
If you look at my thread you'll see I don't use the plastic front diff hangers http://www.oople.com/forums/showthre...=148624&page=6

[Peakey]

Originally Posted by Adam F

My xls suffered badly from front slip, even with a slipper clutch and new belts..

That was with an 8.5 motor..

Would be interested if you find a fix or mill some parts that use a more durable belt..

I'm running a 5.5 in mine at the min but I'm going to change it out for a 6.5

[Npdp72]

Mine doesn't suffer from belt slip. I am running MMS diffs front and rear, new modern belts, slipper, Speed Passion 8.5 brushless motor and lipos. And that's on high grip indoor astro turf surface.

[tahustvedt]

Maybe I need the rear diff as well. It's the front belt that's slippin gin the rear. I removed the front wheel and set te car on a carpet and let it rip several times. No belt slip, and no diff slip as far as I could tell.

Holding the front wheels while accelerating shows the belt stopping and slipping in the rear. I'll try making a smal teflon guide for it so it enders the front diff in the center. It gets really hot because it rubs against the inside side of the diff housing if I tighten it more.

[Peakey]

If you can find one the bosscat 23mm rear diff is apparently the best I have the parts to build a new one but haven't got round to it yet.

[Peakey]

Here it is
http://www.oople.com/forums/showthread.php?t=153145

[tahustvedt]

It works. I made a delrin guide for the front belt. Took me five minutes with my bandsaw and belt sander. No clicking now as I test on the carpet and floor, and no heat because the belt isn't rubbing. Looking forward to testing again. Hope my new bumper gets here soon. I just installed some pan head screws under and taped the undertray shut in the front.

Backing up is an issue. It causes the belt to go to one side and grind the guide on the top. I'll need anothe rguide on the bottom to be able to back reliably.

[Npdp72]

If everything is as it should be the belts should self centre particularly with the standard pulleys which are domed to promote this.
I don't think you should need to resort to making belt guides.
I would strip it, check everything is in good order, alloy gearbox plates straight, screw holes not enlarged, plastic eccentrics and front gearbox housings in good order etc.
then rebuild carefully, trying to make sure everything goes together straight and true.
Be sure the eccentrics are are installed simetrically.
If it still runs off centre try loosening some screws and giving things a tweak to one side or the other until you see the belt centreing up and then tighten things down.

[tahustvedt]

Thanks for the tips. I have tried tweaking the assembly to track the belt. The eccentrics are straight and true. I have not taken the gearbox apart since I started refurbishing it so that may help. I think I'll just wait for the MMS diff to get here. I think it's pretty silly to have no guides on the pulley when the belt is so long. The delrin is just there to let ne drive a little before the diff gets here. I will have a look at the side plates to see if they are deformed visibly.

[tahustvedt]

I found the front of the side plates to be at a slight angle. Upon releasing the tension I found they were not bent, just under tension. I tweaked some more and it now tracks much better. It wanders back and forth inside the delrin guide.

Thanks a bunch.

EDT:
No. The belt was too lose, and tightening it up until it doesn't slip causes it to go left again.