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Just wondering how you adjust the belt tension when converting from an Optima chain to belt drive. With the chain, you'd slip a 1.5mm Allen key under the chain on the top deck and pull it tight. Is it the same procedure for the belt drive, or can you run it tighter? My brief one-page documentation of the conversion installation doesn't cover correct belt tension.

Thanks!

A loose belt is a happy belt.
I usually run belts in belt-drive cars as loose as I can without it falling/slipping off.

I pulled this from another topic in the schumacher forum page. It is a little out of context, but still holds true.

"One thing also that people don't understand is that by nature, belts are intended to be run tight. If a belt has too much play, then the mesh between the belt and its pulley can become a problem. As torque is applied to the drive line, the belt will want to climb away from its mating teeth (read skip), and there will be a pitch difference between the belt and the pulley (belt = a larger raduis, and the pulley's radius stays the same). This will quickly want to wear a belt out, and round over pulley teeth."

Even if the belt isn't skipping (BTW) it can still be too loose. Technically, there are equations supplied by the manufacturer on how tight the belt should be. This is usually determined by the amount of deflection the belt has when a given amout of pressure is applied to a given length belt. A little too complicated for our purposes. Basically, tight enough not to skip plus just a hair. (not enought to play dueling banjos however). Hope this helps. -Jeff

Thanks for that, Jay Dub. I was kind of thinking along the same lines. A chain is less likely to skip a tooth than a rubber belt, and I could tell just moving the belt back & forth that it could "hiccup" with too much play. There's probably less friction with a belt than a chain, so my guess is that it could be pulled as tight as possible with no ill effects.

Of course, if anyone else has info to support or "refudiate" this, please share!

Too tight can be equally as bad, by placing too much tension on drive train parts (causing premature wear), and degrading the belt and its components (mainly breaking down the kevlar or fiberglass belted reinforcement). Good thing is these parts are usually pretty well designed and manufactured. Bad thing is these parts (belts mainly) are designed for specific operating environments and conditions. Definatelly not our particular niche (rc car hobby) especially with the power systems we can currently employ. This is multiplied by the fact that in this situation you are propably using 20+ year old belts that had a manufacturer shelf life of 5-7 years . On that note, I will soon be going a similar route as you with another optima build. Have fun. -Jeff

So the question still remains: How do you adjust it to an appropriate tension? "Keep it tight" and "leave it loose" are subjective statements. The aforementioned procedure of slipping a 1.5mm hex key beneath the belt before tightening the tension is a quantifiable method of setting a specific tension. At least, that's how the manual recommends to properly adjust the chain-drive's tension. Would doing the same for a belt be a good idea?

Well, it fairly difficult with the optima to check belt tension if you are using the belt covers and upper plate, as there is no access to judge tension. However, I would say run the car with the belt adjusted where you feel it should be. Then if the belt skips, tighten it untill it doesn't and go just a little more for running purposes. Unfortunately almost all cars use a trial and error method (accept the original schumacher cats, they gave you an actual mm deflection). However you don't have a bunch of spare belts to figure it out . The good news is that in all the years that I have been running 4wd cars, I have almost never had a belt fail because it was too loose. I have seen belts run as loose as chains, or as tight as a banjo, and still work. Just set it as you see fit ("moderately tight") and see how it works. Good thing is there are plenty of belts availble on e-bay (this is the same belt as the SWB optima mid btw) incase you have a major catastrophy . If you really wan't to know exactly, go to a abelt manufacturers web site, find a belt that is similar to the old kyosho belts, and look up the calcutations/specs regarding that series of belts. (usually it consists of a distance between support points, width of the belt, etc.) Good luck -Jeff

I was doing some research on suspension/performance tuning and found a suitable answer to this question in concrete terms.

With the correct belt tension (any belt-driven car), you should be able to press the belt in at least 1 cm before it goes taut. A belt that's too tight will cause the chassis to flex.

Source:
http://www.rc411.com/pages/howto.php?howto=2

Free the Belts • If you are running one of the many belt-driven cars on the market, this tip's for you. Never run the belts so tight that they may be causing the chassis to flex. This should go without saying, of course, but you'd be surprised at how many cars we've seen with this problem, especially now that most kits offer adjustable differential angles that control the belt tension. The belt should always be loose enough that you can press down on it by at least 1 cm before it goes taught. If it is too tight, it can cause the chassis to flex, and this will almost certainly mess up your car's tweak--and since it's an on-power effect, you may never even notice it.

I always set mine to stop any skipping.

My Turbo Optima runs great with a 19t Mod brushed in fact has lots of speed.

I was not impressed with the belt drive conversion back in the late 80's as the performance was no better.
Just less maintance.. Cost around $160 too at the time.

Funny it's the same belt as the MID.

Mad Racer wrote:I was not impressed with the belt drive conversion back in the late 80's as the performance was no better.
Just less maintance.. Cost around $160 too at the time.

It'll be interesting to compare performance between my two Turbo Optimas--one is chain-drive & mostly stock except for titanium turnbuckles, LRP ESC & mod brushed motor that I believe is 14T, and Project CYANide when it's finally completed. CYANide has the belt drive & will get an EZRun motor, either 3900 or 4300 kv. Haven't decided yet--anyone here have experience with either?

The Optima with the 14T brushed motor is almost ridiculously fast. I can't imagine wanting to go any faster, as it's hard to control!

Coelacanth wrote:The Optima with the 14T brushed motor is almost ridiculously fast. I can't imagine wanting to go any faster, as it's hard to control!

You need more practice

That, too!

I think the belt made a big difference...maintenance wise. I don't believe it increased performance that much. I remember having to adjust the front end constantly due to chain stretch. All that action takes a toll on the chassis rails and screw heads. Also, it made it easier for me to constantly lose screws. LOL! With the belt, you could use some loctite, set it and forget it.