21cc Echo FD

[Chainlube]

Yeah FDs are not for everyone, there is the wet weather thing though thats is able to be overcome as you know.
I would like you see more interest in them. Well done they are pretty bullet proof operationally.
You have made a very nice unit, that I hope generates some sales. The Echo build was a exercise to get a bike motorized with the minimum. The trimmers bearing head becomes the third bearing. I havent pulled one down
yet but there may be two bearing in there. The radial load is on the head not the engines bearings. The drive shaft
is solid steel. Not much to fail. I believe the bike would give issues before the FD.
I think you have a good idea about plans and or parts for off the shelf trimmers. I have recently kicked around a design
to mount a trimmer vertically over the front wheel and drive the side wall. Would keep the weight/foot print central to the bike. You have to have an idler roller opposite the engine but that's a simple loop that would bolt to the fork.

Feel free to pm me if you want to kick around Ideas. I have built many FDs, I like em!

That not might be the best idea, most sidewalls are basically a rag that holds the rest of the tire on the rim.

A short chain to a jack shaft with the roller mounted to it would centralize the weight.

 

[2speedboi]

The side wall thing is interesting idea, but I agree with the floppy rag statement.

We really need Michelin to make a solex style tire for friction drives bicycles.

Thick slicks look nice, 5mm or so of rubber

 

[Cannonball3]

I have seen this crudely done using a vertical shaft mower engine. What a rig but it did work. Dont know
for how long. I would feel pretty confident using some of the ebike tires. I think the Hookworms are probably
up to it. If I ever get caught up with things, may give it a whirl, non pun intended.

 

[Cannonball3]

So drained and filled the tank, took a smidge over 14oz. Ran a course that was clocked with my car at 10 mi.
Total fuel used(drain and read in measuring cup) right at 10oz. Burns an ounce a mile. 128mi/gallon. Im sure this varies
on road/weather conditions, terrain etc. So probably a solid 100mi/gal. The other day when I ran the same course and it
burned 2/3 estimated of a tank, I thought it a fuel hog. Guess not, just a small tank. A small 4 stroke should do even better.

 

[Cannonball3]

Like this. Like the larger clutch. https://www.ebay.com/itm/139F-4-Str...=p2349624.m2548.l6249&mkrid=711-127632-2357-0

 

[2speedboi]

Like this. Like the larger clutch. https://www.ebay.com/itm/139F-4-Str...=p2349624.m2548.l6249&mkrid=711-127632-2357-0

I cant find a clutch size on that unit. What engine copy is this specific 31cc?

 

[Cannonball3]

I assume its a Honda GX clone. Im sure would use the bigger(78mm)? clutch. A pit bike clutch drum assembly
could probably be adapted. I used a Briggs 4cycle on a build, but it was heavy and cumbersome. I didnt run it long.
This at least looks more compact. Price is pretty decent. Listings from $109

 

[Cannonball3]

I think this fits. I modded one of these for a roller years back. Dont remember exactly how but think I replaced the toothed shaft with a 3/8 fine all thread that threaded into a bmx peg. https://www.ebay.com/itm/Gear-Box-C...=p2349624.m2548.l6249&mkrid=711-127632-2357-0

 

[2speedboi]

Yeah it's a large clutch

 

[Cannonball3]

Just get a larger hole saw.