Engine + Gear ratio question

[arndtnew3]

Hi everyone. I am building a cycle car, basically a larger version of a cycle kart. I have a question about gearing and engine choices. My plan is to use a 16-20hp twin cylinder engine, unmodified, with a torque converter, and with a gear ratio of 6:1. I am using 22'' diameter tires. The car will seat two, and without passengers will weigh around 300-400lbs. Would it be possible to reach speeds of around 40 with this setup. I am new to all this, and any advice is appreciated.

Sam

 

[Doc Sprocket]

My gearing calcs suggest that the above combination will result in a theoretical top speed of 39.27 MPH @ 3600 RPM. Be sure to use a genuine Comet 40, rather than a chinese knockoff to ensure that it will put up with the abuse. You should be able to adjust the governor's set point to get a few hundred more RPM out of it if you want to slightly increase the top speed.

For best results, try to shave off as much unneeded weight as possible.

 

[arndtnew3]

Ok cool! Thanks, this is good news. I plan on drilling holes in the channel steel that I'm using for the frame. Should reduce weight a bit, and Ill do some other stuff also. I''ll be sure to get the genuine comet too.

 

[OzFab]

I plan on drilling holes in the channel steel that I'm using for the frame.

Wait up, can you explain that a bit more? Based on what you've said, that doesn't sound like a good idea...

 

[mckutzy]

Ya dont go drilling willy nilly, defiantly might might cause more problems than what you might expect, especially with that higher HP engine your going to use.

 

[arndtnew3]

Im not going to drill holes in the frame willy nilly. Just a few. Whatever I can do to reduce weight. Im not going to ruin the structural entegrity of the frame, dont worry fellows!

 

[devino246]

You'll have to drill a heck of alot of holes to lighten the frame any noticeable amount. You'd be much better off using different material.

 

[arndtnew3]

You'll have to drill a heck of alot of holes to lighten the frame any noticeable amount. You'd be much better off using different material.

Can you please sugest what materials might be better in depth? I want something strong and light. I dont wanna weld aluminum. I wont go the drilling holes route then. I will reduce weight in other areas that doesnt sacrifice strucutural entegrity.

 

[jman231994]

Designing it efficiently is the easiest way to keep weight down. Do you have any drawings or photos of what your making?

Steel will most likely be your best choice, aluminium would be better if designed properly and you could weld it, however as you said, you dont want to weld aluminium.

What thickness and size steel are you intending to use? As too thick or large will increase your weight dramatically and maybe unnecessarily