Mijimobile

[Dan Hunter]

Guess I'm still going to be counting teeth! Uncle!

I've been thinking about it this morning and I think I'll buy a southpaw and disassemble it for the threaded portion and pin it to an Azusa sprocket. I'm inclined to stay with the 20" tires at this point not only because of the cost but to limit the trail on the front end.

 

[Alaskavan]

Dan, My next project is a trike with a 20" rear wheel, so I am watching this closely. How many teeth on the Azusa sprocket?

 

[Dan Hunter]

Ok, my gearbox is actually a G4 which uses a BMX chain and an 8-tooth sprocket...I just counted 'em. Azusa's website has a PDF file on it. They'll sell blanks and choice of tooth count is broad.

 

[gone_fishin]

Guess I'm still going to be counting teeth! Uncle!

I've been thinking about it this morning and I think I'll buy a southpaw and disassemble it for the threaded portion and pin it to an Azusa sprocket. I'm inclined to stay with the 20" tires at this point not only because of the cost but to limit the trail on the front end.

ok, you guys are blowing me away with all the gearing talk, very interesting to watch this one. about the wheel size, tho...why not use 24" on the front also to retain rake & trail? my opinion is it would look even greater still

(of course, cost is a valid factor, i can completely relate)

 

[Dan Hunter]

There's a ton of rake which ensures a fair amount of trail. Project a line down the stem and visualize where it contacts the ground. Then project straight down from the axle. Excessive trail makes the front end rather floppy at low speeds. Nice stability at a high speed, though. With a larger front tire, it'd be aggravated.

I've got an email out to Dave Staton to see if he has easy solutions. I wish he made a billet adapter that had left hand threads and held the 74mm bolt circle sprockets that are used on the crank/front dérailleur on a mountain bike. That would allow for tooth counts from about 24 to 32 and tremendous gear selections. It surprises me because, though not necessary with his gearbox that has something like 18.75:1 reduction, it would really make for climbing power on a mountain bike.

 

[gone_fishin]

well, i was suggesting you change both wheels to leave the basic geometry alone...but as i said, it was only opinion, she's your motoredbike, after all

 

[Dockspa1]

OK then instead of changing the sprocket for more speed and with out losing trail, why not go to a 16" rim on the rear?
doc

 

[5-7HEAVEN]

Dan, what is your reduction box gear ratio?

 

[Dan Hunter]

5:1. You're correct, Viza doesn't give much info on their gearbox. They used to be more liberal with info and proud to discuss it. I waited something like six months for my G3. I don't think they want to be a gearbox supplier. Still, it's very stout and comes with the sprocket and clutch drum that bolts right up to the smaller Hondas and can be adapted with a Staton adapter to the GX50 if you're into four strokes and pulling up to the gas pump and not need a bottle of premix in your pocket.

 

[5-7HEAVEN]

Dan, if you could find a 6-tooth engine sprocket, that'd raise your total gear ratio to 13.33:1. then you'd probably get decent low end and great top speed. this would be cheaper and easier than changing the rear gear.

this would be like a happy time engine with 32t rear sprocket.

Myron