CVT belt live

[bf109v7]

I build myself a diesel bike https://www.dieselbikeforum.com/view ... 1&start=30
but my belt brike after only 300 and some Km. And I dont realy know what to blame for.
What it could be:
Chinese copy of Comet , belt without kevlar
shafts were not parallel by 1,5 °
Thottle got stuck 3 times and I had to stop the enginge by stalling it wit rhe brake
Roller weights did not run smooth cousing steps with interuptions on exelerating
Belt got diesel on it and I cleaned it with brake cleaner.
Does anyone has an other idea what could shorten belt live?
I lined up the shafts, made bronze roller weights whitch run smooth and fixed the thottle cable so it can not get stuch any more, and I will be more carefull nut putting diesel on the belt.
I ordered 10 belts from China, they are stuck in Manila costoms, I hope they will be released next week. And a friend will bring me 2 kevlar reinforced belts in March.
It would be very interesting to me what ist the belt live on your CVTs
Alex

[BertTrack]

What's the gearing to the backwheel like?

What kind of rpm does the cvt make when you reach your top speed (theoretical based on power available)

[bf109v7]

I started with 14:45, top speed was 90 Km/h. But it was hard to go up a mountain and so I changed it to 14:53. Top speed is reduced to 80 km/h, and I think at this speed the engine and the CTV with 3600. Officiel speed limit here is 60 km/h, and there is seldom a chance to go much faster.
Going up this mountain with the 14:45 reduction might also have damaged the belt. Engine RPM went down, and the belt sliped. but this was for 500 m only.
Alex

[BertTrack]

Could you give me your wheel diameter please and the type of tyre. Or the circumference of the backwheel?

[bf109v7]

The circumference of the backwheel is 1989 mm. But I do not anderstsand what this has to do with the livetime of the belt. With the 45 chain weel the reduction is little to long, the enginge will not reach the 3600 RPM. With the 53 chain weel the 3600 enginge speed is limiting the top speed. Probably 50 would be best, but, dont forget, I am in the Philippines living in a very remote place in the countryside. so I have to live with what the lokal dealers have.

[gearhead1951]

As you are so remote I suggest you check out www.backyardmetalcasting.com and http..//gingerybooks.com !

These will get you a foundry for cheap (mostly your labor) and the second will get you a machine shop the same way !

Do a google or youtube search for gingery lathe , milling machine, and drill press to see what can be accomplished !

[bf109v7]

This is not the problem, I am quite good equipped with machines, also I left most of the in Germany. I build a complete airplane, including engine and prop without any qualified help.
The problem is, that I can not understand why the belt broke so fast.
Alex

[gearhead1951]

Mainly because belts are at the edge of their performance limit to start with in that application , ANY additional stress( too tight , too slack , poor alignment Ect....)

That you got all the tools is good , and the metal casting web site will give you all you need to produce parts you simply CANNOT buy as well as parts that are just too expensive to buy ! Check out http://www.crossbreedcycles.net for the " Maserati Bike " in the build log section to see what I mean !

[BertTrack]

The circumference of the backwheel is 1989 mm. But I do not anderstsand what this has to do with the livetime of the belt. With the 45 chain weel the reduction is little to long, the enginge will not reach the 3600 RPM. With the 53 chain weel the 3600 enginge speed is limiting the top speed. Probably 50 would be best, but, dont forget, I am in the Philippines living in a very remote place in the countryside. so I have to live with what the lokal dealers have.

Well i calculated the same thing for my track.

Using the circumference of the backwheel and your final drive ratio 3.78. Assuming you have 1.0 ratio on the c.v.t. when it's fully extended you should be able to reach 113km/hr at 3600 r.p.m.

Now if you say you can only reach 80km/hr on this setup, maybe your belt is slipping, or your engine isn't doing 3600 r.p.m.

Let assume the belt is indeed slipping. Knowing you're not in need of the 113km/hr (and you probably don't have the power for it) you could increase the final drive ratio even more which would make it easier on the belt as the c.v.t.

a 14/70 final drive ratio would give you a top speed at 3600rpm of 85km/hr. Asuming your minimal ratio on the c.v.t. is 1.

[bf109v7]

Thank you for your anwer. Your questions mde me thinking already. I measured the circumfence of the rear weel, it ist 190 cm. The 1989 I had from the Internet. And I made a shopping tour, and I found a 56 teeth weel and a 12 teeth spocket. Of coarse, they do not fit, I have to make them fit, but at least they have the teeth already. And costed only 6 USD.
Calculated top speed at 3600 RPM should be 88 Km/h or 73 at 3000. 73 is about the speed trafic allows here. And with the hevier bronce weights the CVT should go to 1:1. We will see.
So I have something to do wile waiting for belts.
The belts from China are stuck in costoms for 8 days now, I was toled it could take an other 2 weeks.
Alex

[Diesel Dave]

I would avoid using brake cleaner on a belt if you contaminate it I'd use alcohol to clean it.

If my memory is holding up there is an offset on the comet setup between the front and rear sheaves?



This might be for the 44 series only.

I the best wasn't flawed on some way then it's over stressed somehow - either by alignment or the amount of torque being transmitted or the centre distance between the shafts being too short.

I get over 20,000 miles out of a belt on my maxi scooter, but this has a separate centrifugal clutch. I've always thought it was poor engineering to ask a belt to transmit power at zero rpm the way the Comet system does. When I was futzing around with the Comet setup (years ago) I was going to make up my own centrifugal clutch using a tiny car brake drum & shoes.

Best of luck.

[bf109v7]

I know, it was stupid to put diesel on it and making it worse with the brake cleaner. Promis, I wont do it again.
The 3/5" ofset is correct, I had this drawing. And center to center is correct to.
But I got my hands on an RPM meter today, and the engine made only 2700 RPM. Still I think that Bert is right and the belt slipped, because it was pre damaged (narrow) from the bad things* I did to it. I think s because it broke during fast driving, long after starting.
I put the sping in the last holes and reajustet the thottle stop, and the engine makes 4000 now.
I read in this forum somewhere that somebody drove more than 20 000 miles with one belt, so there it should work, after eliminating the wrongs.
Alex

*Bad things:
100 Km with 14:45, and 500 m up a hill with the belt slipping, because the enging lost RPM
2 times stuck throttle cable and engine stalled with the brake.
Sticking roller weights

[BertTrack]

You probably have this right on your bike. But your sheaves primary and secondary so keep the belt straight when changing ratio? The moving sheaves are opposite of each other? (i only found that out late)

[bf109v7]

I have this right, it is like on the drawing. And I just checked it, the belt will stay staight when the pulleys change the ratio.
I have the 12:56 final in now, and, if I would have a belt I could drive. I am going mad.
Alex

[BertTrack]

Hang in there. I know the feeling.

But you WILL ride.

And enjoy it.

[bf109v7]

The 10 belts from China came, and I did ride, and eberything feels fine with the shorter reduction. And the bronce weights. But, after 500 Km the first belt broke.
I hope that the belt with Kevlar will last longer. Did anybody tried both types?
Alex

[bf109v7]

I notised that the pulleys get real hot. And I read that snowmobiles have cooling for the CVT. To protect my foot I made a cover for my CVT. It is good for my foot but it keeps the air of the CVT. So I added a blower, but the Pulleys are still very hot.
And the word whistleblower became a new meaning. I will have to change something to reduce the whistle.
Alex

[gilburton]

https://www.dieselbikeforum.com/view ... 715#p15715

[bf109v7]

duople
Alex

[bf109v7]

I have a COMET 40 clone, and it had bronce bushings, part 6. Parts 2, the cam rollers I made out of bronce also. Original they are iron.
Alex

[bf109v7]

The cooling seems to help, so I did more.

To cool the driver, it would be best to blow in from behind, so I added one more fan on the driven bowing to the front.

And there is a gap between driver and crank housing, and blowing air in there would cool the crank and the inner disk of the driver.

I got the air from the front airstream between crank housing and exaust pipe
And funneled it in this gap.
Let us see what all this does to the belt live.
Alex

[bf109v7]

Belt ran 627 Km now and still looks good. But I hve the feeling it streched and is longer now, because top speed is less with the enginge running full speed. I think, hat the belt does not go to the smallest diameter on the driven, and so the reduction does not go to 1:1. I will dieve this belt till it breaks.
This is the Chinabelt with Nylon Reinfocesement, and Nylon can strech. With the COMET belt and Kevelar reinfocesement the belt should not get longer, because Kevlar does not strech.
Alex

[UAofE]

Even with Kevlar it will still change functional ratios as the rubber wears.

[bf109v7]

750 and still running.

[mark_in_manchester]

I'm following this with interest - I really like your air-cooling. So - still running? And your 'foot protector' - looks good. Fibreglass, or something else?

A few years back I also followed the path to madness referred to by a contributor to one of your threads, and got involved in home-metal-casting. If you like machine tools (and are living remotely and I assume trying to recycle as many materials as you can) then you might like to give it a go - it's great fun. A burner running on a mix of waste engine oil and diesel is easy to make, and furnace lining can be clay / sand mix rather than expensive hard-to-obtain stuff. But perhaps you have a life with actual worthwhile activities in it!!