need advice to mount sprocket on chainsaw (no welder available)

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azguero

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Hi i am trying to biuld a chainsaw bike but have no idea how to mount the sprocket, it has a clutch so dont want friction drive but worried about taking housing off as i dont want to ruin the clutch... any ideas??? Thanks in advance, also i am mounting this to the front wheel
:-|| scratg
 
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azguero

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i just realized it got putin the wrong section my computer sucks i tried posting in general but i guess i was stilll on this one, i will remove but as to eliminate your confusion my idea is to mount the engine in front of the handle bars and run the chain down to a sprocket off of a mtn bike front crank and bolt it to the spokes such as the motor kit sprocket does, but i have no way to mount the sprocket to the saw
 
Bikeguy Joe

Bikeguy Joe

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bigbutterbean said:
you say no friction drive, but your mounting the engine over the front wheel? only possible front wheel drive i know of for a bicycle is friction drive.
Click to expand...
bigbutterbean is wrong.

You can mount a sprocket to the front wheel using a "rag joint". You can put a centrifugal clutch on the chainsaw with a sprocket, and run a chain between the two.
 
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mat_man

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Hi Azguero

Unless you are using a 16" or smaller wheel you are going to need a jackshaft reduction.
Something like 18 to 1 reduction is what you need.
 
Bikeguy Joe

Bikeguy Joe

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He won't need a jackshaft either, as long as he has enough reduction with the sprockets....say 9 tooth drive, 60 tooth driven.

I know you don't want a friction drive, but I have seen a very simple set up using the chainsaws clutch drum running right on the tire. The guy built it in 15 minutes.
 
wayne z

wayne z

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Dec 5, 2010
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mat_man said:
using
http://www.diygokarts.com/speed-calculator.html

8/52 gears with 12" wheels gives 49mph at 8888 rpm

with this setup you would need a BIG chain saw motor, min of 88cc
Click to expand...
But I think he plans on using 26" wheels, and with your numbers, the gear calc in the DIY forum calculates to 105.8 mph at 8888 rpm.

To get useable rario without a jackshaft, he will need a sprocket about the size of his wheel rim. Similar ratio as running the clutch drum against the tire.

There was a front wheel drive build here recently(Lowracer? Lowrider?) where he used a 26" bike rim for a sheave and a belt cent clutch on the motor.
 
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mat_man

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Azguero

I did see a youtube video of someone using a dremal tool to shape the chainsaw clutch teeth to fit some kind of bike chain. I would not advise this.
 
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azguero

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the bike i have is a 24'' i dont have many resources at the moment unfortuantely i like these ideas i think im going to play around ith it a little and see what kind of frankenbike mess i end up with lol im just trying to get motorized somehow and i get the feeling i may be trying too hard as i usually do and then end up doing the simplest thing and having something solid but it seems to be one fail after another lately,,, i put the chainsaw on rack on the rear of the bike and ran a normal chain to gear 4 and reached behind to throttle it, but without modding the saw the chain slipped alot (but worked somewhat) MAIN issues was pedals turn using this method but it was a mockup and ratchet strapped down (very painful in the end)
 
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azguero

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.dd.daxtit
mat_man said:
Azguero

I did see a youtube video of someone using a dremal tool to shape the chainsaw clutch teeth to fit some kind of bike chain. I would not advise this.
Click to expand...
i actually did consider this and as i only need to go about eight miles it COULD work but what do you think the risks could be using this method becuase it almost works as is
 
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mat_man

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I think the video had something like 6 teeth, this small number would be hard on the chain and sprocket. The hardness of the steel, I suspect would be
lacking.

I would go with a friction drive and a drop clutch.
 
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azguero

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only problem i have with friction is i would need to find a peg or something and cut out the plastic on the saw or break it off but i might have to just do it as long as i can get work without having to pedal (wind always seems to blow both directions)
 
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mat_man

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Bikeguy Joe

Bikeguy Joe

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As I said, you can run the clutch drum right on the tire for a friction drive, if you can remove enough of the housing. There is a thread on here somewhere where a guy did it.
 
killercanuck

killercanuck

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I remember that thread Joe, I think it was This Guy, with the wood saddlebags.

That's a good idea attaching a cut up cassette for ratio changes. Would need decent welding skills though.
 
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mat_man

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Yes Bikeguy Joe, I have seen the youtube video and it looks like it works well,
BUT running the numbers for a 54mm clutch:

(2.13" * 7777rpm) / 336 = 49 mph

It would work best for a rider under 150lbs, willing to pedal up to 15mph first,
45cc or bigger, and willing to ride in a tuck.

Also a slick bell housing would not work well in wet conditions. Not sure if you could glue
some 36 grit sanding belt on.
 
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NormO

NormO

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I don't know what the problem would be with shaping the teeth of the sprocket with a dremel. I did it around a year ago and have had absolutely no problems. I've had more problems with the clutch and drum glazing and slipping more than i have sprocket problems. Wetness doesn't seem to bother the clutches at all believe me on this one. If it's a concern cut a small diamond hatch pattern in the shoes. This all comes down to gearing as well. A nice starting point is 20:1, but 30:1 is better.
 
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