Friction Drives

I like friction drive but not a lot of others seem to be as enthused as I.

I'm planning a friction drive with a 33cc motor on a MTB. Deacon has inspired me.

I've ran a friction drive stand-up scooter for years. The only negative thing I didn't like was I was constantly getting flats. The spindle would drive whatever (thorns, nails, staples or glass) was stuck in the tire deeper. But besides that I was happy to own a 44 mph scooter.

I am gonna go that way. and I have been thinking about it for months

If you don't have any serious hills to climb a 33cc friction drive should be cool. My lil 25cc does great on flat and minor hills but put it on a real hill and it just cant do the trick.

I am thinking seriously and I even bid (I lost thank god) on a chainsaw motor from ebay. I think I can use it with the clutch and sprocket to drive a rear wheel china sprocket. Something about 42cc is what I have in mind. I keep hoping someone can tell me what it will do so I don't have to wander into it. lol.

I just had a thought, I wonder since the chain saw motor is so light, how it would do as a front wheel drive with that china sprocket. Why I would do that I have no clue. Just a random thought from an electron misfire in my damaged brain no doubt.

But I do love friction drive. It is the easiest way to get power to the wheel. I never had the flat problems just the moisture problems. Standing water on the road will give me a sudden but temporary loss of power. Riding in the rain is a no no, but then why would anyone want to.

Thanks deacon, I was wondering about how much displacement was enough. 33cc is enough then thats great. The larger stuff is a bit more expensive.

I have been keeping a close eye on your project, because I have been wanting to do the same thing. I also share the same concerns for the front wheel drive, but I think it might be unlikely to throw you forward because of the wheel spinning away from the forks when the bike is moving forward. I was also wondering how the steering might be affected by the extra weight.

Finding an engine thats adequate for a front wheel drive set up might be the hardest part though.

I mounted mine on the front for a day. It seemed to do okay but I just couldn't get all the stuff juggled right.

I think now I have the ideal solution for me at least.

1. The engine always stays in good contact with the rear wheel.

2. I pedal it down my short drive in full choke.

3. I switch to half choke for half a block after it starts.

4. I turn off the choke and just pedal away.

5. At about four miles an hour it will start.

6. It will shut down automatically when it slows below that speed. (If you have good constant pressure on the wheel.

7. I can start pedaling from a reasonable uphill and have it start no problem much better than even the china girl bike. It is much lighter. Now there is more drag on the rear wheel so it is harder to pedal than the bike would be without the engine but it is doable.

Downside:

You can not just pedal it. the engine will start. I will be carrying a tool kit to take the nuts off the engine hold down to release it. That is just in case of major problem far from home. I'll just tie the engine up and go.

I am still in the test phase but I learned something new today. Even the 25cc which I had no previous experience with has a threaded shaft. It was hidden behind a spacer of some kind. I found the when the spacer unscrewed itself for me by accident. I am now having a new drive wheel welded.

Also I found out that almost all new home improvement store trimmers have the same engine. the two hundred dollar trimmer has a 31cc ryobi engine and so does the 69.99 model.

If you live in a reasonably flat area the 31cc should take you all over the place no sweat. So even if you go new its 75 bucks for the engine another 75 or so for a wallymart bike and a little more for assembly parts, and you have a motorized bike.

I know even here I can get a working 31cc engine at the flea market for 35 bucks and a used bike for 25 bucks. Twenty five more for mounting hardware and for under a hundred bucks you are riding to work instead of walking.

When I am finished with this experimental project, I plan to do a parts list and step by step to convert a weed whacker to bike engine instructions.

If you have hills like me you might take a look at used backpack blower engines. Some of those run 40cc and of course chainsaws

Thanks for the information Deacon! I am staying tuned.

Update on the 25cc engine..

I loosened up the friction drive so that it would skip when it went into overload. It still doesn't skip much but it runs a 100% better. I made my tie down bar adjustable and now I'm going to work on getting it adjusted correctly.

Here is the good news, the bike pulled itself and my fat butt up all the hills. Yes it dropped significantly in speed but on the test track it did run up all the hills. I pedaled on one just to keep the speed up.

It has never had a new spark plug and I'm sure the plug is a hundred years old so I'm going to spring for one in the next day or so. I am not going to tear this one down but I am going to build one with the 31cc ryobi engine to see if it is significantly better on the hills. This one is suicide going down hill wide open. I just need a little more umph on the uphill side.

I am going to hit the lawn mower repair shops next week and look for a 31cc engine at least. But I can tell you now this is a very doable project but I still need to work on getting the tension on the drive right and try a slightly larger engine.

I hope the ryobi 31cc will work because it is readily available at very reasonable prices.

Now one of those chainsaws would be good... I actually think I would like to try the 31cc next just to see if there is enough there. I would like to find the minimum cost for one.

I might have 500 in mine but the next guy could build one for a hundred bucks I think.

The reason I really got interested in a cheap bike build was when I was walking for my health I would meet a young black woman who had to walk about two miles to the mall every morning to work there. I thought how nice it would be for her to arrive there without all the sweat and starting out the day tired. Probably no one would want one for that reason. I'm also hoping seniors will build them to get out and have a little fun plus keeping them active a little.

these bikes are good for my balance as well... Today for the first time since I was a teenager I stood on the pedals to get more leverage. I have been terrified to do that till today. I didn't think about it, it just happened. I tell everyone this is the best thing I have ever done for myself.

Wow, check this friction drive out...this guy used what look's to be a alternator for the drive



I guess he would just run a fan belt from the motor to the alternator...I guess it would not be that bad if you had a guard for the belt

Wish I had thought of that.

Now that is homegrown ingenuity! I like his way of thinking.

Well I rode my rather plain (by comparison) weedeater bike with the galvanized pipe (plbg dept of home depot) drive again today. A lot of how the bike does is i how I ride it. The bike needs some assistance but it's more about when I give it the assistance.

When I start from a stoplight the engine is totally dead. It starts about five miles an hour which isn't much. The trick is to pedal it hard even though it has started for a while. Pretty soon even on small hills it will roar wide open. Then it can keep up for quite a while before I have to pump it up a little.

with the short pedals and the small drive chain the bike has to get to almost stall before I can comfortably override the free wheel mechanism. Then I just pedal like heck till the motor roars again. It is a good idea to just use two speeds on the motor. idle and oh my god if that chain breaks I'm a dead man.

But the bike is a lot of fun. If I need to run an errand i still use the china bike. I am looking for a 35 to 43 cc engine to build a new friction drive, then I might just dump the china bike on the next guy with a couple of bucks who shows an interest.

On the next and I hope final build I plan to mount the engine much closer to the rear seat and possibly lower. I might hang a saddle bag type thingie off the other side to kinda balance the look of it.

Okay, I went looking for a motor for my next build. I couldn't find the used week whacker man, so i went to the big lots store. They often sell factory refurbs. I found a poulan 33cc chain saw in an open box. The chain had been stolen.

To make a long story short after a ten minute wait the manager arrived. She and I did a little tap dance and I bought the engine for $50 plus tax. Now I have to test it, then figure out how to best use it. Definitely friction drive. I might have tried to use it on a sprocket if it was 45 or more cc.

So I have the first part of the new build on hand. Anybody know anything about chainsaws. I'm going to try to save the centrifugal clutch.