What size drive roller?

[DamoMotorized]

Put two weedwhacker engines on the bike, one for front and rear.

I did that with two 2.2hp Mitsubishi engines. It was awesome.

Haha

I could, i got 5 working weed wackers that people threw out (they just needed new fuel lines) but its too much work.

 

[DamoMotorized]

Damo: Download, install, and run the bike power calculator.

Plug in your desired max speed, the bike weight, your weight, and set it for flat conditions with zero wind speed. That will give you the approximate power you need to run under those conditions. In your case, since your engine is already spec'ed, adjust the max speed up or down until the power required matches what you have available. For a friction drive, you should be able to use 90% as a rough efficiency.

Then, download one of the gear ratio calculators and calculate the gearing to achieve the max speed above, for your friction drive.

When you introduce slopes into the calcs, things get a bit more complicated. Measure the angle of the slopes on your hills, plug that angle and you/your bike's weight into the power calculator, and adjust the max speed until the power doesn't exceed your engine's power. Then, plug that speed and your engines max power RPM into the gear calculator to get the roller diameter size.

Thanks for showing me these. I've used the "gear rat" one before. It says that i will be able to go 38.46 kph (23.84 mph) at 6000 rpm with a 3.4cm (1.34" spindle) which i'm definitely happy with.

The bike power calculator tells me I will need 1 hp (which approx is how much my engine has) to get to 38.46 kph (23.84 mph) with no hills/wind.

Thanks

 

[BiMoPed]

Its been a long time and i still havn't finished this project. But now that i have long school holidays i will be able to finish it. Would a 3.5 cm (1.38 inch) roller make a big difference over a 1.25 inch roller. Remembering that I have only put on about 6 kg since the first post making me around 56 kg (123.5 lbs) now and not that many hills.

1.25" is probably too big
1.125" / 1 1/8" is the right size
Yes, 1/8" makes a difference

 

[DamoMotorized]

Just a quick update. I ended up buying a 32mm (1.26") pipe. I am just waiting on these bearings to come from US: http://www.vxb.com/page/bearings/PROD/Kit7345. I will show you guys in picks how it will all look when i finish. Once those bearing come from US, pretty much all I have to do is just put everything together.

 

[DamoMotorized]

1.25" is probably too big
1.125" / 1 1/8" is the right size
Yes, 1/8" makes a difference

1.25" is going to be ok. Have a look at this bike: http://www.youtube.com/watch?v=WY-4p4sa03k he is using the same engine and drive roller diameter as me and it runs great. Plus he probably weighs about double my weight.