slipping belt

Discussion in 'Rack Mounted Engines' started by Torques, Jun 10, 2007.

  1. Torques

    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.
     

  2. OldPete

    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.
     
  3. Torques

    Torques Guest

    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.
     
  4. OldPete

    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.

    [​IMG]

    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
     
  5. Torques

    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. :shock:
     
  6. OldPete

    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.
     
  7. Torques

    Torques Guest

    Thanks, I'll get back to you.
     
  8. Torques

    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.
     
  9. OldPete

    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.
     
  10. locoWelder

    locoWelder Guest


    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! :evil:
     
  11. bamabikeguy

    bamabikeguy Active Member

    Go to a Mom and Pop hardware store, they have a drawer of springs.

    Buy 2 or 3 different tensions on one of those #18's. Cost about a quarter.

    Pick the best type.

    Unwind about 2 inches from each end, wrap through the hole under the tension knob, and then around a strap hole. It is a backup for the tension spring, which compensates if you screwed around with the factory torque on that damn nut.

    Here's a collage, before the spring idea dawned on me. Before I found out cheap batteries won't run a camera very long.

    [​IMG]


    I'm catching up, guys, the phone hangs up three times in every 20 minutes out here in Rough Edge.

    BTW- Sheave is BOGUS. :? The orderform spells it SPOKE RING. Any more sheaveshooting is prosecutorial. :cool:

    Centered on 12 gauge spokes, no need for superglue, add the spring and it will make up for screwing up the SPOKE RING snap on. :cool:
     
  12. Torques

    Torques Guest

  13. Jim H

    Jim H Guest

    Torques, I had a similar symptom with my GEBE 40 tanaka. Have you checked the spring? Mine broke and I replaced it with a slightly stronger one from the hardware store.Maybe this will help.
     
  14. Jim H

    Jim H Guest

    Torques, the metallic sound you mention... sounds like it may not necessarily be metallic but may be the sound associated with the teeth of the belt slipping on the spoke ring. Is it a sharp sound or a softer, muted sound and can you feel it as well? My belt is currently doing this too. Mine is attributed to my wheel being slightly out of round and at top speed I get the wawawawa effect. I'm currently running a rhyno-lite with 14 guage spokes, one of which was broken and since replaced but am considering going to 12 guage and a professional shop to do it. I suspect that this out of round condition is what is causing yours and my belt slippage. Nothing wrong with the product, we just need some righteous maintenance.
     
  15. Try This

    I had the same problem....you can hear the belt "click" from time to time, letting you know it's slipping. Do you have a quick release axle on the back? If so, your mounting strap will ride too low on the quick release, and cause the belt to be too long. Even though your tensioner is still engaged, and riding the belt, it is at the wrong angle to effectively keep the belt tight. Loosen your axle, and raise the mount strap up so that the bottom of the strap rides even with the bottom of the axle nut on BOTH sides. Also there is the posibility that you may have torqued down the hinge on the tensioner arm, preventing it from swinging freely. Loosen the self locking nut on the tensioner arm a half turn, and try it then. Add a drop of oil to that hinge as well.
     
    Last edited by a moderator: Aug 26, 2007
  16. bamabikeguy

    bamabikeguy Active Member

    The .39 cent fix

    GEBE says the tension arm is "correct" when shipped, and I try my best to avoid adjusting that tension.

    If you've done everything "right", and this is proven when you take the first ride and the tension arm "barely" bounces, the belt is centered on the drive gear, no rubbing on the tire or frame.

    But still there is a "click" at certain speeds. The "click" arises from the spoke ring, changing from trail to highway gear doesn't solve the click.

    Here's the solution I found, #18 springs- 2 inches long, giving a second "insurance" tension to the arm. WORKS EVERY TIME !!

    Same as the "insurance" zip tie from top of the strap down to the fender bar.

    When 50 Red Chinese touched the bike, plus all the workers down the line on the engines, mounts, shipping, there is NO perfection, and sometimes a small add on like a spring fixes everything.

    Besides, the only way to see how the rear end is spinning and bouncing and springing is to follow on a second bike, riding at 30 mph, and who can really do that?

    Another thing, the belt takes about 1/4 mile to "warm up" sometimes, belt noise disappears after it has flexed a few hundred yards up the block.

    btw: I drug up one of those old WallyWorld Avalons, gonna use to do the frame mounting that seems to be catching fire on the forum.

    It has an aggravating kickstand attached to the axle, frame mounting fixes that too. Okay for a demo-ride bike, but I don't trust em for selling to the public.
     

    Attached Files:

  17. Jim H

    Jim H Guest

    My experience is this... after I ride a couple of miles the belt warms up and I don't hear the clicking of the belt or feel the belt slipping. When it does slip, I reach behind me and apply tension to the belt and it stops. The spring I replaced isn't strong enough to keep proper tension but that's an easy fix. I also have to be patient and allow the bike to warm before wot. Will check out those 2" #18's though...
     
  18. Torques

    Torques Guest

    Thanks for the excellent help.
     
  19. Torques

    Torques Guest

    I have adjusted, during many rides, the tension of the spring. It shouldn't be too loose or too stiff. If it is too loose, the clicking is worse. If the tension is too tight, I believe there may be a greatly increased friction or pressure issue possibly resulting in worse gas milage and increased wear. Sometimes, I do seem to "just about get the tension right" but it seems I have to baby it, not too much throttle at slower speeds or it will click. I have a 13 gear on my prototype and will shortly convert to a 12 tooth one.
     
  20. belt slip

    Don't forget to at least try increasing the distance between your rear wheel axle, and the drive gear/pulley on the transmission. Again, if your motor sits 1/4 inch too low, it will put the tensioner at an awkward angle, (too much slack in the belt), and the belt has more leverage than the spring. This causes adjustments in tension by the tensior arm/spring to be sluggish, and a slippage can occur momentarily until the arm "catches up". Worked great for me just to raise my engine off the axle maybe 1/4 inch. I would also advise against excessive tension by heavier springs, due to the constant "pull" on the rear wheel drivering. I've noticed mine slide slightly on the spokes when engaging the tensioner. Not a good thing. I would almost think that it is the main function of the tensioner, to compensate a little for "off center" driverings, which occur when the drivering is wearing in, and it becomes a little loose on the spokes. Only speculating of course!!
     
    Last edited by a moderator: Sep 6, 2007
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