Tension warning

Discussion in 'Rack Mounted Engines' started by Jim H, Aug 29, 2007.

  1. Jim H

    Jim H Guest

    My belt has been making more noise than usual lately, just kind of complaining with its clicking under low load and I thought the tension idler needed extra help, ie., more tension. Added an extra spring so it's tight... on my way to the next town, three miles out from my house the belt gave way. Luckily it wasn't eighteen and I pedaled home. The short of it is this... my belt had been talking to me for about a month telling me it was tired and maybe coming to the end of its life. By over tightening the tension I helped to shorten the life of the belt by stretching the belt and the plys giving way at the weakest point. I guesstimate that I have 2000+ miles on this belt. That's not bad when you consider it has taken some time to feel and understand this system. The longer you ride a gebe, the better you come to know its nuances. Excessive tension on the belt, bad and gebers, listen to your ride it's talkin to ya!!!

  2. srdavo

    srdavo Active Member

    XLENT advice!!!! No matter what you ride!!
  3. Jim H

    Jim H Guest

    New belt and gear arrived today, will install this coming Tuesday... after looking things over I realize that another contributing factor to the belts demise is the drive gear and drive ring are not lined up. I replaced my rear wheel and didn't take into consideration that the two wheels were different manufacturers, etc, etc... the broken belt was also frayed on one side. Will make the necessary adjustments and post results later. Live and learn! BTW, I don't think the tension was as much the culprit as was the allignment.
  4. Torques

    Torques Guest

    Jim, thanks for the info. The only problem which I have previously mentioned was the skipping/clicking issue. I will follow what you find out, thanks again.
  5. Jim H

    Jim H Guest

    Ok, couldn't wait for tuesday and installed the new belt today. The belt wasn't tracking dead center on the drive gear so I loosened the two engine mounting bolts and moved the engine ever so slightly until I was as near to center as possible and retightened. That's the ticket I think, will know when I get a ride in.
  6. Jim H

    Jim H Guest

    Just went for a 5 mile putt to see how the thing is handling... while I was installing the belt I also upgraded to the 14 tooth gear, 13 being standard. I have no speedometer but could tell the difference in top speed was increased. At my normal speed that I ride the engine revs were decreased significantly... instead of a high "reeeeee" it was more of a lower "wuhhhhhhhh". That's about as descriptive as I can get. Good to be on the road again...
  7. Jim H

    Jim H Guest

    Wasn't satisfied with where the belt was tracking so added a washer behind the drive gear... the belt is now centered in the gear. I was still experiencing the clicking issue prior to this adjustment and have yet to test drive it as I've been on duty here but tomorrow is a designated mb day so will post further results after a long ride.
  8. bamabikeguy

    bamabikeguy Active Member

    Mine is clicking, it's on the "down"circuit of the belt, looking at it "10 oclock" on the spokering, when the belt leaves the grooves.

    I'm a thinkin', and its only come up SINCE framemounting, and it doesn't happen on all 4 bikes, that adding a washer or two, down on the axle, might shift THAT part of the equation, make for a truer belt circuit.
  9. Jim H

    Jim H Guest

    Rode 50 miles today and paid close attention to the nuances of the bike. Here's the stuff... the belt is tracking perfectly, nary a click, slip or abnormal sound did I hear out of her, gas mileage was increased on this ride because of the higher drive gear(14 tooth). Ordinarily I would refuel much sooner. The rpms are at a more comfortable level; easier on the rump and ears. Not knowing precisely the mph of this setup, I can say that it feels like a 4 to 5 mph increase in top end. Will get a digital speedo today to satisfy my curiosity. Overall I'm satisfied with the present tweaks.
  10. Jim H

    Jim H Guest

    Rode and tweaked today, added a trek speedometer and observed mph with 13 vs 14tooth drive gear. Also the thing was clicking and slipping... cured that with a tad more tension by adding another spring. Imo, the 40cc Tanaka requires a bit more tension due to it's torque. The engine mount assembly is used for all gebes engine configurations. Anything above 33cc's may need that additional tension to keep the belt tight enough that it doesn't slip. I'm happy w/ the results of that tweak. OK, mph and performance! The 13t drive gear gives better takeoff (less pedaling) and is a good combination of power and top end, my top speed is 28-30 on the flats, 32.8 slight downhill run. Cruising on the flats at 3/4 throttle 26-28 mph, depending on wind. The 14t gear needs a little more pedaling at takeoff but not really an issue when the belt is seated and properly tensioned. top speed is 31-33 on the flats, 34.8-35.2 slight downhill run. Cruising on the flats at 3/4 throttle is 29-31 mph. The rpm's are lower when cruising and the torque is slightly diminished but the 40 is quite a torquey little engine so it's not very significant. When I get a day to ride for a few hours, I may have to update my findings but at the moment these are accurate. As rack mounters know, it takes a certain amount of finesse to get the performance that these setups are capable of. So in summary, tension, allignment and takeoff (pedaling and throttle combined) are interrelated to a successful and productive ride and keeping our rubber on the road and out of the shop.
  11. GEBE Belt Break Warning Time

    Hi Jim,
    I also just completed a GEBE belt replacement. I had a two week period where I noticed that the belt seemed to slip a little more than usual when going up a 10 degree grade hill (I can gauge the slip by how much I have to pedal! ...I thought I was growing OLD...turns out it was the belt! :grin:). A few times, I pushed the tensioner pulley down to ensure engagement. I noticed some very slight fraying on both sides of the belt. Then, at the start of a casual ride, the belt BROKE. Luckily I was only 1/8 mile from home. This first belt lasted 797 miles but the short life could have been due to my learning process and hilly terrain. See my Intro where I am keeping a log of my experiences (2 entries in this link, latest update is 9/21/07) - http://www.motoredbikes.com/showthread.php?t=5772

  12. Jim H

    Jim H Guest

    Ray, did it actually break as in severed, or did it like let go and overstretch to uselessness?
  13. GEBE belt breakage (picture)

    In my case, the belt broke on the tooth side of the belt while the belt backing stayed intact. I stopped the engine as soon as I detected massive slippage. If I ran the engine longer, the belt backing might have broke as well. In the picture, I bent the belt backwards for better visibility.

    From the picture, one can see the frayed fibers. Inspecting the rest of the belt, there are a couple of other places on the belt where fiber fraying has started on the belt edges. The peak of one belt tooth looks like it is splitting. These are definite signs of general wear.

    The actual breakage happened going downhill. I think going downhill is very hard on the belt. This is because the bike is moving at its own speed, only restrained by the drag of the belt. When the engine is revved up, the clutch engages at 4kRPM (on my stock GEBE 35cc) and the belt is suddenly forced to run at the speed of the engine. This can put a great instantaneous stress on the belt if the engine speed is not matched to the wheel speed (very hard to do), and is definitely a higher stress than just starting the bike from a dead stop.

    ************ New information added 9/23/07pm ************
    With all the discussion that has been generated by my belt breakage observation, I wanted to add a few additional comments
    * This is my FIRST experience with a MB. So, part of my experience is to push the design as far as I can to see what the limitations are. Then, I can figure out how to adjust my riding to increase performance or system longevity or whatever.
    * My riding includes some very hilly areas. I commonly ride up and down 7-10 degree grades which are rather steep. One of my concerns, from the beginning, was how well the GEBE system could take steep hills.

    After breaking my 1st belt, and thinking about why, I have concluded that the premature failure was due to how I engage the engine going downhill. If the bike is picking up speed coasting downhill (steep) and then the engine is engaged at a low 4krpm, the belt will experience a sudden jerk which, after the fact, I now know is too hard on the belt. That explains why my belt broke when I went downhill and engaged the engine.

    I can think of three techniques to remedy this -
    1) Coast until I am only going about 15mph. Then, engage the engine as usual. This is approximately the speed at which the centrifugal clutch happily engages and is similar to a rolling start. I did this on my ride today and the belt sounds very happy, with no flopping or snapping sounds.
    2) Coasting downhill at high speed, then engage the engine/clutch by using maximum throttle all at once (do not use anything less than maximum throttle!). The idea is to make sure the centrifugal clutch is spinning AT OR ABOVE the speed of the bike wheel when engaging. Instead of belt jerk, the centrifugal clutch should slip and push the bike faster, minimizing stress on the belt. This can be tricky because the bike could still be going faster than the motor/clutch can support.
    3) Go downhill fast (above 15mph), keeping the engine engaged all the time by giving the bike gas. This way, there is no switching of the clutch from off to on. Since the engine is always engaged, there are no extreme sudden stresses exerted on the belt.

    After all this, I think technique 1 is the best for short steep hills, and technique 3 is the best for long steep hills. I am not sure about technique 2...I need to try that in a real world situation to decide.

    I wanted to add these additional comments because I didn't want people to prematurely judge the GEBE design harshly because of my firstime experience, without knowing some of the extremes I put the bike through. I am still going through the learning curve of understanding the design's strengths and weaknesses, and adjusting my riding style accordingly. I am expecting to achieve many more miles on the 2nd belt (already 50 miles of hills today with no problems).

    Attached Files:

    Last edited by a moderator: Sep 23, 2007
  14. smapadatha

    smapadatha Guest

    I've noticed this too. Going down a steep hill, I previously would not use the throttle since the hill itself was giving me quite a bit of speed. The drive belt would start to oscillate madly. I could hear it and feel it. Intuitively it seemed like this would be bad for the belt, so I would brake to slow down and then use the throttle to minimally engage the engine. The belt oscillation stops immediately. After reading your post however, I'm going to be even more aggressive about controlling this type of belt oscillation on hills. Eight hundred miles per $25 belt is quite a lot of money (although still trivial compared to the cost of car repair).

  15. larymor

    larymor Guest


    Is there anyplace else to get belts?
    The $25 you quote for a belt Sam...is that total price with shipping? I got a replacement plastic drive gear cover for my Robin under warranty, and had to pay $7 for the shipping. I think they should have paid the shipping...anyway...:cry:

  16. Jim H

    Jim H Guest

    25+4 shipping&handling from gebe=29 bucks. Yeah if I suspect that I'm only going to get 800 miles per belt I'll have to look into a chain drive from Staton but as it is, I estimated close to 2000 miles on my first belt; I can live with that easy enough though I ain't made of money.
  17. larymor

    larymor Guest

    I got 225 miles on my belt right now and it doesn't appear to be wearing at all yet. No slipping..fraying etc. It just seems $25 for a belt is a lot of money... I know they need to make a profit, but I suspect that is probably five times their cost....they have kinda like a monopoly....where else ya gonna buy your electricity?
  18. Jim H

    Jim H Guest

    I've been googling Gates for this particular belt and can't find a definitive part number, only partial. The number reads on my belt 16355M09KSPCL... all I get is 16355M09 and a link to york industries so york carries it for Gates and gates has it as well, however it's difficult for me to understand fully not being an engineer so that's all I have at the moment.
  19. Alaskavan

    Alaskavan Guest

    Jim, I suspect that the KSPCL is shorthand for Special, i.e. a part made particularly for Gebe. I have access to the NAPA parts computer system. I'll see if I can find anything out about it tomorrow. I also suspect that it will not be much, if any cheaper through Gates.
  20. GEBE Belt Life Observations (added)

    I amended my original post (about 7 entries before this one), with some thoughts on how to prevent premature belt breakage.

    In regards to GEBE belt pricing, I also think the price of $29 each is high. However, this is a low volume business, and i knew before embarking with my 1st MB that this ***is*** a proprietary belt design. For these reasons, I gladly pay the price for belts, allowing the inventor to recoup development costs and even make a profit.

    Now, as a consumer having just bought replacment belts, I feel challenged to make each one last at least several thousand miles! :grin: