gas/engine speed/roller/speed/rear wheel speed relationship

[mifletz]

Where I live in the north of Israel there are NO flats at all! Everything is either a very steep hill up or a very steep hill down.

Good job I listened to Staton and got the smallest 7/8" roller, as it can just cope. Anything bigger would be near useless.

The only problem is having to constantly raise the roller on the down slopes, less the engine over rev. Can making over-use of engine breaking downhill damage a Robin 35?

 

[andyszyd]

4 stroke engine like Robin EHO gets lubricated no matter of throttle position. You can go downhill with no problem. Considering engine breaking effect + roller friction resistance you will not overrev engine, just do not go much faster than your max speed is on the flat.

I was doing 27Mph downhil (with pedal assist) wide open throttle on my Robin EHO 35 with 1 inch roller.

I calculated my RPM at 27 MPH with 1 inch roller is 8400-8500 RPM.

 

[Pirate88179]

Where I live in the north of Israel there are NO flats at all! Everything is either a very steep hill up or a very steep hill down.

Good job I listened to Staton and got the smallest 7/8" roller, as it can just cope. Anything bigger would be near useless.

The only problem is having to constantly raise the roller on the down slopes, less the engine over rev. Can making over-use of engine breaking downhill damage a Robin 35?

You could buy a BMP 1.250" diameter one-way roller and have a local machine shop turn the OD down to your 7/8" size. The one-way roller is great as you can coast totally freely.

Just a thought. The shop would then have to add some scoring to the surface again for traction.

Bill

 

[andyszyd]

I don't think you can machine down BMP 1.25 roller to 7/8 without affecting freewheeling mechanism.

There must be a reason BMP does not make 1 inch frewheeling roller, only the 1.25.

But to be shure one can check with James at BMP.

He is one of the best and most friendly guy to deal with.

 

[Pirate88179]

You are right. I just measured mine and it appears that you would not want to take it down to much below 1.00" OD. This would leave enough material to house the one-way needle bearings and still give you a .200" plus wall thickness. I can get better measurements if I take my roller off but these numbers are pretty close. Going down to .875 (7/8) would probably make the wall too thin and it would not have good integrity.

Bill

 

[Happy Valley]

BMP doesn't make those rollers, they are industrial overstock from an electric bike that is out of prodution. They were only produced in the 1.25" size and are made from mild steel, hence their tendancy to wear so fast.