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slipping belt

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Torques

Guest
I have the same symptoms on my prototype, slipping belt now. The tensioner, when I watch it, moves up and down about one quarter to one half an inch. The gear wheel is almost exactly round at speed. I really can't figure out what's going on. Any suggestions? Thanks.
 


O

OldPete

Guest
I do not know what the max run out is for the sheave but Dennis did say, via telephone, when they install them, that <1mm is good.

I will have to buy spokes and lace my wheels before I can speak from a hands on point of view. My rear hub will be here Wendsday and wheel 'n hub are needed to figure spoke length.

But! Dennis, of GEBE, did say that they lock the sheave to the spokes with 5 minute epoxy after it has been centered. I will epoxy every spoke that can be epoxyed to a spoke just for overkill. The surface of the sheave under the spoke and the surface of the stainless spoke will be broken with med grit sand paper for good adhesion.

I think the sheave is not running true. It's off center.
 
T

Torques

Guest
Ol' Pete said:
I do not know what the max run out is for the sheave but Dennis did say, via telephone, when they install them, that <1mm is good.

I will have to buy spokes and lace my wheels before I can speak from a hands on point of view. My rear hub will be here Wendsday and wheel 'n hub are needed to figure spoke length.

But! Dennis, of GEBE, did say that they lock the sheave to the spokes with 5 minute epoxy after it has been centered. I will epoxy every spoke that can be epoxyed to a spoke just for overkill. The surface of the sheave under the spoke and the surface of the stainless spoke will be broken with med grit sand paper for good adhesion.

I think the sheave is not running true. It's off center.
Pete, what do you mean by this, "max run out is for the sheave"? About the "sheave is not running true", please tell me what you mean, thanks.
 
O

OldPete

Guest
To protect the seat stay, wrap it with some tape.
Attach a piece of wire coat hanger with several zip-ties to this protected stay.
Bend the wire so it almost touches the top most edge of the sheave.
Turn the wheel slowly and see how far the wire gets from the edge of the sheave.
You may have to adjust the wire several times to get it to where it will just touch then leave a gap 180 degrees later.

I do believe the sheave must be removed inorder to get it recentered again...If it is found not to be concentric to the hub.

Yes! The hub..not the wheel, because the wheel may not be concentric to the hub.



The outter circle is the rim and its distance from the hub can vary as the wheel turns. Poor wheel lacing would permit this, so I will never use it as a guide for a sheave install, unless the rim is found to be very true. The rim could be used for a good rough quess-ta-ment otherwise.

The inner circle is the sheave, it must have the same dimention or distance from the hub/axel as the wheel turns.

If the rim is not concentric to the hub two things will happen.

1-The wheel assembly will be way out of balance. Fine, it can have weight added to bring it into balance. No big deal, most will say.
I don't like weights. They look bad and indicate poor wheels or lesser than tires...in my mind. (i have pre-balanced cast motorcycle wheels by bonding lead inside the outter edge of the hub before the tires are mounted and generally no further weights are needed)

2-The tire will run hotter than one running true because the tire must flex more to make up for being out-of-round. This too is no big deal if one is not running long distances, on hot days, carrying a heavy load(my 240#), plus pulling a trailer. Hot tires have shorter lives and are the ones that blow out.

If the sheave is not concentric to the hub

1-The belt can bounce 'n slip. It does not have teeth all the way around for a reason. And I think that reason is to permit a degree of poor installation or out of round. If it had teeth all the way around, there just might be a chance it would eat some of the rubber teeth off the belt if the belt bounced off the sheave just enough for slippage.

2-Rubber hates heat and this out of round will cause more heat build up in the belt drive than is necessary. Belt life will suffer.

I think the FAQ section over at GEBE talks about how much the tensioner handle can move and still be OK. It is not much. You might consider going over there for some reading. :cool: I did last month.

See where it says radial truing? That's what we are addressing. For both the rim and the sheave. The sheave being the more important of the two.
http://www.parktool.com/repair/readhowto.asp?id=81
 
T

Torques

Guest
Thanks for the thoughtful information. There is nothing I can find out about this condition from GEBE. It is not in their faq section. I have spun the wheel numerous times and see very little wave in the gear ring, I mean very, very tiny, front to rear, not side to side. The tension roller bobs up and down (about 1/4 to 1/2 inch) while I'm riding and slips under above medium power application. This condition just started (1100 miles). I would say the rim is as true as my Glide deluxe with 4500 miles. There is no difference in off-center movement between the two. :eek:
 
O

OldPete

Guest
Check very closely for a tiny rock caught inbetween the belt teeth or in the drive sheave. A 1/4" is too much for me and a 1/2" is insane...Something is wrong.

Sorry about the FAQ comment. I did read it, prolly in one of the reviews over at GEBE or via a google search of comments on their kits.

A new belt will cost $25 so you might consider calling Dennis or emailing tech support over there.

Dennis got a little angry at me when I cancelled my wheel order, preferring to build my own. The 8 sets of wheels I've built, so far, came out near perfect, but I did start with very true, new rims. Everything was +or- .003"...no kidding. This sheave will add a new challenge.
 
T

Torques

Guest
Just got back from a night ride, it's doing the same thing, slipping. Even when it's not slipping it's making a noise, like wah wah wah, almost sounds like a slight metal scraping sound but I absolutely can't figure it out yet. I'll take a look at it tomorrow in the sun. There were no rocks in the belt, everything looks ok there. I have a spare belt, maybe I should put that on to see if it fixes it but if it does fix it, then 30.00 for a belt every 1100 miles would hardly be economical.
 
O

OldPete

Guest
I don't know. The only other two things that come to mind are, does the belt have a bad teeth or section that's ruptured in it? And are the bearings that support the drive sprocket OK?

Good luck and keep us posted. Hope there is resolution.
 
L

locoWelder

Guest
Torques said:
I have the same symptoms on my prototype, slipping belt now. The tensioner, when I watch it, moves up and down about one quarter to one half an inch. The gear wheel is almost exactly round at speed. I really can't figure out what's going on. Any suggestions? Thanks.

yea you know what it's shot can't be fixed you just need to give it away....I'll take it off your hands for ya! :devilish:
 
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