Do I need any gears on my bike? What options do I have?

[unclejemima]

So, I'm going to be converting my tadpole trike to electric real quick...only problem it has 120mm dropouts, and a SRAM 3spd internal hub gears...and no front de-railer.

The 120mm drop out is no prob, as its just a steel frame, so I'm going to just bend the frame to 135mm.

It appears that I probably cant put a rear de-railer on the back either, becuause it does not look like my bike has the proper mounting brackets on the back? (see attached photos)...and the seat post tube is a weird shape, so I probably can't mount a front de-railer either...?

Do I need any gears? I guess if I go DD hub, I can still pedal until the speeds get stupid fast...and going up a hill I have the electric power to help me up.

What sort of sprocket sizes should I run if I can only have one gear...and is it even possible for me to fit at least a front derailer?

Are there any electric hub motors with a internal gear system, or CVT?

Looking for advice...

[amberwolf]

If the motor you're gonna use can do all the work for you, you don't have to worry about gears, unless you want to be able to pedal it under varying conditions without the motor.


If there is room for even a few sprockets between the motor and your rear dropouts, you can use older / cheaper type rear derailers, which don't require a hanger-bolt-on as part of the frame. See
http://www.disraeligears.co.uk/Site/Fal ... le%29.html
where the "hook" at the top is? That goes over the axle, and a little bolt goes thru the hole to the side of it, with a nut that matches the end of the dropout slot, to keep it from pivoting.

Since the axle of the motor has flats on it, you don't even actually need the little bolt.

[BATFINK]

You could install a schlumpf drive on the front and a single speed cog at the rear?

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[BATFINK]

That would give you 2 gears one easy to pedal and one where you could really contribute when your at higher speeds.

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[Chalo]

So, I'm going to be converting my tadpole trike to electric real quick...only problem it has 120mm dropouts, and a SRAM 3spd internal hub gears...and no front de-railer.

The 120mm drop out is no prob, as its just a steel frame, so I'm going to just bend the frame to 135mm.

It appears that I probably cant put a rear de-railer on the back either, becuause it does not look like my bike has the proper mounting brackets on the back?

Those are very ordinary front opening horizontal dropouts. To fit your trike with a derailleur, you just need to get one with an integral hanger claw. They are cheap and easy to find.



If you want to install a nice quality derailleur instead of the cheap kinds that have integrated hanger claws as an option, you'll need an adapter claw. You bolt the claw onto the frame, and attach any bolt-on derailleur to it.

Do I need any gears? I guess if I go DD hub, I can still pedal until the speeds get stupid fast...

It borders on insanity to consider going fast on that trike. It's set up entirely wrong for fast travel. Too high, too narrow, can't lean into a turn. The thing will throw you right onto your head the first time you try to turn at 20mph. What you have there is a weird grandpa trike-- keep safe by limiting yourself to weird grandpa speeds.

Are there any electric hub motors with a internal gear system, or CVT?

The SRAM Sparc, now long out of production, was a 5 speed internal gearhub with two small electric motors built in. It was lightweight, but not very powerful (250W), and it had a top speed of around 16mph. That's more than fast enough for your deathtrap, but acceleration and climbing would not be very impressive.

Chalo

[dogman]

One gear can be plenty, it just depends on how the bike is used. What ratio you pick may depend on if you want to pedal till you reach a too fast to pedal along speed, or use the motor till you can pedal along at top cruising speed.

Personally, I'd just slap a derailur from a cheap MTB on it, the kind that bolts into the slot on the dropouts. Then even if you ride in one gear all the time, you get to pick that gear after you finish the build, instead of taking a guess at which gear you will prefer.

[spinningmagnets]

Simplest and cheapest is probably add a triple chainring to the bottom bracket. Would involve having a derailleur-mount welded in the right spot, or perhaps fab an aluminum block that clamps onto the lower seat-tube.

Nexus and Sturmey-Archer (SA) make a 3-speed trike hub, with a second sprocket on the shell, and the stock separate freewheel sprocket (which has a changeable tooth-count). You could make/adapt a U-bracket to hold it halfway from the pedals to the rear wheel.

If you are a handy fabricator, you could make an adaptation plate to add the shell-sprocket onto a Nexus 7-speed.



A possible mount-bracket donor ($20?)


problemsolversbike.com has a sliding "bolt-on" bottom-bracket, so you can place the pedals farther forward. If the diameter of the clamping part is too small, you can buy a raw frame-builders BB-tube, and have it welded to your frame.
http://problemsolversbike.com/products/sliding_bottom_bracket_shell/

[unclejemima]

Thanks all for the reply's.

Those are very ordinary front opening horizontal dropouts. To fit your trike with a derailleur, you just need to get one with an integral hanger claw. They are cheap and easy to find.

Good to know...

If you want to install a nice quality derailleur instead of the cheap kinds that have integrated hanger claws as an option, you'll need an adapter claw. You bolt the claw onto the frame, and attach any bolt-on derailleur to it.

Cool. I would imagine that I can purchase this from any bike shop? What are they worth? You say it will bolt on, with hose clamps or similar?

It borders on insanity to consider going fast on that trike. It's set up entirely wrong for fast travel. Too high, too narrow, can't lean into a turn.

Agree'd, its very tippy, but I can two wheel it around corners as long as I initiate the lean before the corner. Then I can corner as fast as any bike. It gets heads turning to see thing 2 wheeling around the trails

[unclejemima]

The thing will throw you right onto your head the first time you try to turn at 20mph. What you have there is a weird grandpa trike-- keep safe by limiting yourself to weird grandpa speeds.

lol. Actually, i'm not even 30 yet... I guess I like weird stuff ...but i really bought it because I live in northern Canada...6 months of the year is snow, and with a regular bike, even studded tire, results in laying the bike down at least once a ride...not with this reverse tadpole trike!

I'd like to be able to do 20 mph on the the straight familiar sections, just so I can actually get home faster on my commute

[Chalo]

If you want to install a nice quality derailleur instead of the cheap kinds that have integrated hanger claws as an option, you'll need an adapter claw. You bolt the claw onto the frame, and attach any bolt-on derailleur to it.

Cool. I would imagine that I can purchase this from any bike shop? What are they worth? You say it will bolt on, with hose clamps or similar?

You see that screw in the picture? It has a funny hat-shaped nut on the back side. The nut goes in the back of the dropout slot, and the claw bolts onto the outside. The axle of your hub will therefore sit about 1/2" forward of the rear of the slot, and you may have to adjust your brakes a little if that's a different place than where the wheel sits now.

My shop sells the claw with its nut and screw for $4.

Have fun and be careful. Your machine should give you some good times as long as you keep it right side up. Sounds like you know what you're getting into, though.

Chalo

[amberwolf]

You see that screw in the picture? It has a funny hat-shaped nut on the back side. The nut goes in the back of the dropout slot, and the claw bolts onto the outside. The axle of your hub will therefore sit about 1/2" forward of the rear of the slot, and you may have to adjust your brakes a little if that's a different place than where the wheel sits now.

As I noted in my reply way up the thread, since the hubmotor axle has flats on it that would probably match up with the flats on the slot of the adapter, you very likely won't even need that little bolt--simply sliding it over the axle and tightening down the axle nut should be sufficient. Then the hub can seat all the way into the dropouts.

You could still use the bolt if you like, but you don't have to, if the adapter does fit across the flats "tightly" enough. The only thing you have to deal with without the bolt is that hte derailer will come off with the wheel when you take the wheel out for any reason.

[unclejemima]

Cool. Thanks for the kind reply.