D.I.Y Gearbox

3 posts / 0 new
Last post
Mr. Sander
Last seen: 14 years 4 months ago
Joined: Monday, December 3, 2007 - 12:02
Points: 5
D.I.Y Gearbox


I would like to have some response based upon below idée, the sketch is about to show a gearbox device for my newly acquired second hand 750W Bosch engine. According to the motor maker the engine output is about 3300 rpm. it is little to fast for direct connection to the wheel. The initial plan during my hopeless struggle was to have another second hand heavy duty planetary gear, however the planetary gearbox has lots of metal fragments inside it is basically broken or it should definitely be destroyed during frequently use.

Next on the list: How-to make your own gearbox, I have chosen spur gears, they are ok price vice, sound level would be ok if I'm using z1 + z2 > 60. I will try to mount in axels as stiff as possible. There shall be one bearing one each side of the gears. The assembly would be in a aluminum housing and as I understand that the housing must be carefully made by keeping the axial distance within a few hundred of millimeters. I'm lucky to know a guy that have a small mechanical workshop. Else I do not think it is possible to be within required axial distances. So any comments to this setup?


Mr. Sander

To-Do before EV take off: Battery 100% Charger 100% Engine 100% Controller 40% Gearbox 10% EV Frame ?%

Last seen: 14 years 11 months ago
Joined: Tuesday, November 21, 2006 - 13:01
Points: 137
Re: D.I.Y Gearbox


I don't have any experience of building electric bikes (that's what you want to do, right?), but I think you are making things too complicated. As you write, the gearbox requires high precision, something that is difficult and/or expensive to achieve.

What gear ratio do you need? Depending on the actual load rpm of the motor and the size of the wheel, you might need a ratio of between 1:5 and 1:10. That could be achieved by a chain setup, even though a high ratio requires a very large chain ring. In any case cheaper and less demanding. And easier to adjust the ratio as well, if necessary. If that doesn't give you enough gearing, try to simplify the gearbox to only one stage, perhaps 1:3, then the remaining ratio with a chain drive.

Another option is a toothed belt setup as first gearing stage. Also very robust and doesn't require that high precision, but has slightly higher losses.

Hope this helps or maybe gives you some new thoughts at least.

andrew's picture
Last seen: 14 years 4 months ago
Joined: Tuesday, November 28, 2006 - 17:21
Points: 1361
Re: D.I.Y Gearbox

Sander, I 2nd what rgx said. Martin makes virtually every sprocket/belt one would ever need: http://www.martinsprocket.com/sprockets.htm Which can be sourced from an industrial supplier.

A cheaper option is here: http://www.surpluscenter.com and also here: http://www.electricscooterparts.com/sprockets.html . Some of the sprockets at that last source include a freewheel mechanism, and those small sprockets will handle the power just fine.

[url=/forum-topic/motorcycles-and-large-scooters/587-my-kz750-electric-motorcycle-project]KZ750 Motorcycle Conversion[/url]
[url=/forum-topic/motorcycles-and-large-scooters/588-fixing-my-chinese-scooter]900 watt scooter[/url]
Pic from http://www.electri

Log in or register to post comments

Who's online

There are currently 0 users online.

Who's new

  • Mohammadawawdy
  • Jiya
  • volejbol
  • Gordongadget
  • Cold Rider

Support V is for Voltage