Bernd wrote:krokodil wrote:Those chassis are quite nice, just the speed reduction seems to be to small. For the modern motors we need a gear with over 1:20 reduction ratio. This cannot be achieved with belt drive. ( the worm gear has a reduction in TT around 1:8-1:12, that means the belt drive should have additionally at least 1:2 reduction.)
What do you mean you can't get low reduction with a belt dive. Take a look a Nigel Lawton web site. Here's a link to his pulley and belt products. It looks like you can get up to 1.1 to 11 reduction.
http://www.nigellawton009.com/DriveComponents.htmlBernd
You can, you just do not have the space in TT. If the smaller pulley let us say has a root pulley of 2 mm the overall diameter will be over 4 mm
The second pulley must have root pulley of 4 mm, its overall diameter is 6 mm. This would be 1:2 ratio. Not very efficient as the belt on small diameter will tend to slip.
If you select bigger pulleys, like root 4 and 8 mm, you will be already almost out of space between the wheels because the bigger pulley will have an overall diameter of 10 mm.
The maximum space between the wheels is 10.2 mm.
I just wanted to point out the limitations of the belt drives in this form. Maybe you had a chance to have the Athearn RDC with beltdrive. It was a nice experience how not to build a model vehicle.
Additionally there is always a tension on both axles and on their bearings. That is why some people use ball bearings for beltdrives.