X-5 squared shredded belt and pulley!

[Fiddybux]

Hi all,

Was at the Southport meet today and was getting some good advice on how to best setup my X-5 squared. Everything suggested worked a treat, which had me leading the pack in the B final until the car ground to a halt.

At first the general consensus was that I had stripped the rear diff, but having opened the car up it seems that the diff is intact (all good), but the belt was in bits, yellow bits everywhere, the fibres inside the belt had wrapped around the belt tension pulley and the slipper pulley was completey rounded.

The slipper pulley is not the crappy stock one either, it was the small Losi pulley from the centre shaft in the XX4. Now it is good only for the bin!

So, I want to know if anyone has had this before, what caused it and how I can avoid in future?

I wonder if I had the belt too tight and this is what caused it? It felt okay to me, skipping slightly under hard braking only...and it is meant to skip a little.

I also wonder if I should have blunted the edges of all the pulleys and diff gears when assembling to help prevent belt damage. I will certainly do this now with a small file.

Any ideas anyone?

Cheers all.

[super__dan]

Hhhhmmmm, chicken or egg?

I have only stripped a Losi pulley once, at last years Euros. I'd incorrectly set the belt tension and it was far too slack but cos it was a qualifier I carried on anyway. By the end most of the pulley teeth and a fair amout of the belt teeth were stripped.

Not sure what to suggest, both are quite robust normally.

[MikePimlott]

How Mad is this.
This happened at Batley today to Stu Hurley. At first Mr Long thought it was the rear diff but on further inspection the belt had torn to bits and wrapped all around the pulley.

2 in one day. Hmmm

[hickston]

Car was ace though :-)

[Fiddybux]

That is proper mad! Stu and I need to confer on this matter!! Mine looked very similar to the photo's, except my drive pulley was just a yellow colour and it was the belt tension pulley that had belt fibres wrapped around it. All bits of yellow belt everywhere as well.

I'm a bit suspect that the belt was too tight for another reason....when braking hard on concrete I sometimes nollied the car and sometimes flipped over front ways!!!! I got so much grip on the front that the back just lifted into the air. Had the belt slipped a bit more here then I don't think this would have happened....but what do I know!

Any other ideas why / how this happened?

[Chrislong]

Im wondering, if both you guys have had the belt running up against the side of one of the gears somewhere? or tensioner? More than likely the layshaft/slipper gear I think, but if its rubbers away the side then chewed the belt, and side of gear breaks away (like in Stu's picture), belt moves aside and as you rev it a 5zillion rpm, it goes into meltdown.

When you two rebuild the transmission, just check to see if the belt runs up the side of the gear. The way to stop it, is can moves shims around layshaft to adjust where the gear is, for small adjustments. Can also shim out the tensioner pulley, or flip the diff gear over (as it is marginally off centre), but don't just flip the diff as the bolt will go the wrong way - take diff apart and flip just the gear.

Erm. I have never experienced this, so don't shoot me if im wrong with the above.

[Fiddybux]

No Chris....this all sort of makes sense to me.

In the tuning section of the manual it warns about making sure the belt runs true and straight in all the pulleys and tells you how to do it...but this is only for reasons related to "efficiency".

I guess though it is how it started, a little chaffing on the edges of the belt soon turns into a big old ripped belt at very high RPM that you get in this car. I mean, with the Losi pulley, the internal ratio is a stupidly small 1.68:1 I think!!!

As to how the pulley got rounded is a little beyond me at present...maybe heat induced through running fast with a tight belt?

In any case, when I rebuild I will definitely get everything lined up in the middle to avoid contact with the edges as much as possible....plus I'll get a few belts and pulleys for spares just in case!

Wish I could be certain how this all happened though.