Gearing Ratios

[OldPete]

I look at it from the tire's perspective.
Convert mph into fpm vs the tire's circumference to rpm.
1mph = 1.46667fps
So if the engine peaks at 7k rpm, just figure from there.

Silly but it works for me.

 

[SlicerDicer]

pete...

12 tooth to 30 tooth to 10 tooth to 36 tooth on a 26 wheel? I do not understand how the 30/10 tooth would be calculated...

Would that make it so the rear tooth was equal to 36x3 being a 108 tooth? as in 30/10 reduces it by a factor of 3? I do not understand gearing very well

 

[OldPete]

30/12=2.5

36/10=3.6

2.5x3.6=9.0 to 1 reduction.

Most 26" tires are 2 meters around or 6.5'.

An 18 to 1 reduction will offer about 28mph w/a 26" tire with the engine at 7k rpm. just a guess-ta-ment

 

[SlicerDicer]

the RPM for full clutch engagement is 2300rpm and the top speed of the motor is 3600rpm.

So that would mean about 15mph at max 3600rpm and about 10 at engagement?

 

[gone_fishin]

ok, so now you "adjust" by changing that intermediary sandwich. again, i'm no help with the actual math :???:

 

[SlicerDicer]

that math is beyond my head too..

 

[SlicerDicer]

Ok now that the gearing ratio has been basically answered. Here is the dangerous part...

How to reinforce the rear wheel? LocoWelder got any ideas how to reinforce a wheel to be hell for stout?

I am afraid of ripping all the spokes off in one shot when I get metric tons of torque on that wheel..

 

[OldPete]

What size and type of wheel you looking for?

 

[SlicerDicer]

26 inch wheel for mountain bike with 7 speed cog.. the cog will be welded if needed.

Is there anyway to reinforce a normal wheel to handle 3.5hp and not shred?

 

[OldPete]

Golden Eagle has rear wheels that are laced 4 cross with 12g spokes for a very good price. Shipping is $20 though. They come in silver or black, packable bearings or sealed bearing type(disc brake). The disc brake type hub can be used on a V brake anyway(I think the rim's side wall is finished for V brakes? Better ask if you go that way.). Could even mount a drive sproket where the disc rotor mounts for that matter.

Google 4 cross lacing and road speed gear charts, there are lots of hits for both.