custom tricycle project please help

[BigT]

Ok so I have a tandem tricycle bike. It has 2.seats side by side .2 seperate cranks so each person can peddle . I got a wild hair and wanted to put a motor on it to help with hills. It has bmx gearing so hills suck bad.
I bought a Chinese kids 110cc quad. It's electric start and automatic. No gears , just start and go. I mounted motor and am using a jackshaft kit. The gearing is a 14 tooth on motor to 14 tooth on jackshaft drive input sprocket. Near the tire it goes to a 42 t sprocket on jackshaft output to 21 t sprocket on rear tire. The tires are 22" bike tires. Right now the bike has ZERO bottom end torque...I have to pedel really hard and the motor just bogs ...the jackshaft gear ratio is 3:1 but I don't know if extra sprocket (21t) on tire throws off ratio. I have hills near my house and need lots of bottom end torque. Top speed isn't a concern for me. Any help is appreciated . I can post pics if it helps

 

[BigT]

I would like help getting gear ratio around 7:1 or maybe 8:1

 

[landuse]

OK, you have a big problem here. With you having a 14T on the engine and a 14T on the JS in, you might as well not have a jackshaft, because the initial ratio on the 'In' side is giving you 1.

You gearing as it is now looks like this:

(engine teeth/JS in)*(JS out/axle) You divide the bigger by the smaller

So (14/14)*(42/21) = 1*2 = 2:1

Your gearing is 2:1. That is so high that I am surprised you are even moving. What you have to do is look at different sprocket combinations to give you at least that 7 or 8:1 ratio that you are looking at. Having 2 14T sprockets on the same side of the jackshaft makes it useless as a jackshaft.

You could get another 42T sprocket and have your combination like this:

Engine - 14T
JS In - 42
JS Out - 42
Axle - 14

This will give you (42/14)*(42/14) = 3*3 = 9:1

You will probably find this is much better than the 7 or 8:1 that you are looking for because of the diameter of the tyres. I have a minibike which I had to gear to 11:1 before I got any decent torque out of it.

I hope this helps

 

[r97]

If you can, put the 42t on the tire, the 21t on the jack shaft "in", keep the 14t on the engine, and put the other 14t on the jack shaft "out". That would give you a 7.5:1 ratio. I'm not sure how well that will work because a lot depends on the engines internal reduction, but it should at least give you a starting point without having to buy more stuff (assuming you ca switch the sprockets).

If that ratio is too low try switching the 21t and 42t sprockets from where they are currently, and put both 14t sprockets back where they were.

A third option is to ditch the js (if possible) and run the 14t on engine to 42t on axle.

Right now you have a 1:2 ratio, not a 2:1. In other words you have an overdrive instead of a reduction.... bad.

 

[qtband]

Please let us know what happens!

 

[landuse]

Post some pics of your tricycle. I am interested to see what it looks like.

 

[BigT]

You guys are a lot of help. I think I have a 60 tooth sprocket I can swap out. O have been pulling my hair out trying to figure this out. I will pull bike out today and take some good pics and post. Maybe ill get video and post it

 

[BigT]

I'm limited on swaping sprocket because the 42 and the 21 are both bicycle sprockets and the motor 14t and js 14t are for a 41 motorcycle chain..

I can go
Engine 14t
Jackshaft in 60t. 4.2:1
Jackshaft out 42
Axel. 21 2:1 8.4:1???

That should get me to 8.4:1 if I'm figuring this out right??.
Little more cutting and a little more welding

 

[Leftythenub]

I'm limited on swaping sprocket because the 42 and the 21 are both bicycle sprockets and the motor 14t and js 14t are for a 41 motorcycle chain..

I can go
Engine 14t
Jackshaft in 60t. 4.2:1
Jackshaft out 42
Axel. 21 2:1 8.4:1???

That should get me to 8.4:1 if I'm figuring this out right??.
Little more cutting and a little more welding

Jackshaft out 42
Axel. 21 2:1 8.4:1???

This is all wrong. You divide the driven (21) by the driver (42) and you get 0.5: to 1 ratio. Your final drive ratio would be 2.1:1. You need to get rid of the 42t sprocket and replace it with a 10t sprocket. Can you post some pics so I can see what you are working with?

Thanks,

Lefty

 

[BigT]

here are a few pics of the tricycle project maybe this will clear up gearing issue

 

[BigT]

By the way I have a kids trailer to tow behind bike also...torque is a must

 

[Leftythenub]

Just switch the large sprocket and the small sprockets on the jack shaft. It may not be ideal, but it will be better.

FYI:
Chain Dimensions

Chain Pitch Btw Inner Plates
25 1/4" 1/8"
35 3/8" 3/16"
40 1/2" 5/16"
41 1/2" 1/4"
50 5/8" 3/8"
420 1/2" 1/4"
428 1/2" 5/16"
520 5/8" 1/4"
530 5/8" 3/8"

#41 chain is the same pitch and size as bike chain except it is wider. You could probably get away with using it to power the bike wheel.

 

[r97]

Okay, well I think the thing for you to do is this:

1. Switch the 42t and the 21t, that will give you a 2:1
2. keep the 14t engine sprocket, and purchase a larger "JS in" sprocket.

Now you are going to need to figure out what size sprocket you need to get. To do that you should either know the size of the sprocket that was used on the engine's donor vehicle and its tire size.

OR

You need to find out the primary reduction ratio, and all the transmission ratios of the engine. Also we will want to know some specs on the engine (hp, rpm, etc). With that information we can run some numbers to figure out approximately what size sprocket you need.

 

[Leftythenub]

Hey BigT, I forgot to tell you about OMBwarehouse.com. They are a great place to find parts for minibikes and gokarts alike.

http://ombwarehouse.com/home.php

 

[Bluethunder3320]

ahhh those jackshaft bearings everyone has problems with them including me.

they always self destruct
might have to upgrade to pillow blocks soon

and plastic rims. be careful. haha.

 

[r97]

I did some research and found out the common chines 110cc atv has:

16" OD tires
14t engine sprocket
40t axle sprocket

engine primary reduction of about 3:1(???)

So.... after some rough estimates I would say you may want to try a 28t on the JS in, although I cant make any guarantees. Hopefully some other members will give their opinions on that number too.

 

[BigT]

The rear sprocket on the quad it came off of was a 36t . It still lacked enough bottom end . I'm going to try a couple things an will give an update

 

[BigT]

Engine 14
Js in. 60. 4.2:1

Js out. 10
Tire. 21. 2.1:1

Over all ratio 8.9:1
Should be plenty of bottom end

 

[BigT]

video

http://www.youtube.com/watch?v=K4MMhj2g7ys&feature=youtube_gdata_player

This is the bike almost 100% done

 

[anderkart]

Nice job BigT

I was kinda wondering if the kid might be breathing exhaust fumes back there...