Using 3-speed hub, how to make auto-shift?

[Urban Fatbiker]

The difference being that if it's a CG bike engine there's no slight buffer like an auto clutch and that your bike engine is about 32 cc and a four stroke.

And driving the power through using the hubgear as a jackshaft isn't going to make it any better, you're spinning it 5 times faster than it normally would turn, so the engagements will be at higher speeds. This also will fling the gear lube off the sun and planets. Expect to lube it more far often and it will leak all the oil you've added.

But you know, go ahead, you are the expert, right?

Uh, can the snark. I'm the one asking. I'm no expert. Its an idea.

I haven't started on this yet, and still looking for someone that may have done it, good or bad.

LRJerry is running thru the drivetrain with derailleur. You are offering detail based on your experience with 3-speed hub mechanics.

Neither is proof of application using a 3-speed hub under power as a jackshaft, although LR has shown another way to skin this cat. You warn why the hub may not work. I appreciate both inputs.

LIKE I said, I am no expert on this, thats why I asked.

But getting rude about it to me? I am an expert in rude. Prefer not to exercise that expertise. Be civil.

 

[Sidewinder Jerry]

The difference being that if it's a CG bike engine there's no slight buffer like an auto clutch and that your bike engine is about 32 cc and a four stroke.

And driving the power through using the hubgear as a jackshaft isn't going to make it any better, you're spinning it 5 times faster than it normally would turn, so the engagements will be at higher speeds. This also will fling the gear lube off the sun and planets. Expect to lube it more far often and it will leak all the oil you've added.

But you know, go ahead, you are the expert, right?

Have you ever attempted to build a bike that shifts motor driven gears automatically? If not then you have no idea what it will or won't do. Experts told me my bike wouldn't work and yet I'm riding it. Keep you ears open and tell me if you hear any banging through the gears?



I do believe UrbanFatBiker should use the Kilduff shifter though. The shifter can be adjusted for the speeds he wishes it to shift at.

 

[Sidewinder Jerry]

LewieBike it's good that you're presenting possible problems. Now I challenge you to give solutions to how to make a 3 speed IGH shift under motor driven power automatically. Don't think for one minute the auto shifter rear derailleur on my bike is a stock LandRider auto shifter. I've made mods to it. If there's internals in the IGH that need to be modified then lets work on figuring out what they are. I see real potential here if a team of us can do this

 

[Urban Fatbiker]

We do have time to figure this out. Its the season for Tour De Nash, I'll be on my fatbike working the human propulsion for the next month.

This auto-shift is going on a recumbent I'm building, will return to that build after the Tour.

Street-legal, and total isolation of human and engine is important, as I ride a lot of parks around here. My favorite loop includes sections of a 13-mile flat bike trail.

And I'd like to power to TDN next year and have the Metro police bike patrol impressed...motorized street legal, hill-climber, AND bike park friendly recumbent with the expansion-spring floating seat like my last one.

 

[LewieBike]

LewieBike it's good that you're presenting possible problems. Now I challenge you to give solutions to how to make a 3 speed IGH shift under motor driven power automatically. Don't think for one minute the auto shifter rear derailleur on my bike is a stock LandRider auto shifter. I've made mods to it. If there's internals in the IGH that need to be modified then lets work on figuring out what they are. I see real potential here if a team of us can do this

Jerry, I go from observation of over 30 years professional bicycle mechanic experience. Gear hubs, by a large margin have much weaker internal stress resistance to driving loads. This is very true with Shimano 3 speeds made in the 1960's and 70's They had a reputation of 'exploding' under hard use. You might get an old Sturmey AW to last somewhat under really gentle shifting, but if you use an old S-A AW that 's already worn. it's only going to fail that much quicker.

Honestly, the only way I see this working is to have some sort of momentary ignition kill or timing retarding that coincides with the shift point function. Sturmey 3 speeds have a huge gap in the 2nd to third shift point, that you can hold the trigger halfways between these two shift points and be completely out of gear like a neutral in a motorcycle transmission. If any power gets applied while this point is transitioned, you will destroy the gear hub. I've seen idiot kids do this to a bike thinking they were "powershifting' a 3 speed hubgear.

Car automatic transmissions make their gear changes with friction bands, not dogs and claw pawls and cross clutches. A car auto transmission engages smoothly because the torque converter and the brake bands buffers the engagement.

 

[Sidewinder Jerry]

Jerry, I go from observation of over 30 years professional bicycle mechanic experience. Gear hubs, by a large margin have much weaker internal stress resistance to driving loads. This is very true with Shimano 3 speeds made in the 1960's and 70's They had a reputation of 'exploding' under hard use. You might get an old Sturmey AW to last somewhat under really gentle shifting, but if you use an old S-A AW that 's already worn. it's only going to fail that much quicker.

Honestly, the only way I see this working is to have some sort of momentary ignition kill or timing retarding that coincides with the shift point function. Sturmey 3 speeds have a huge gap in the 2nd to third shift point, that you can hold the trigger halfways between these two shift points and be completely out of gear like a neutral in a motorcycle transmission. If any power gets applied while this point is transitioned, you will destroy the gear hub. I've seen idiot kids do this to a bike thinking they were "powershifting' a 3 speed hubgear.

Car automatic transmissions make their gear changes with friction bands, not dogs and claw pawls and cross clutches. A car auto transmission engages smoothly because the torque converter and the brake bands buffers the engagement.

What do you think the results will be with the 3 speed Shimano Nexus and the Kilduff shifter running through the crank using a shift kit?

 

[JerboaJohn]

what engine will you be using?

 

[Sidewinder Jerry]

what engine will you be using?

Myself personally I'd stick with what I know. It isn't so much about the engine type (2 or 4 stroke) as it is more about using a centrifugal clutch coming off the engine. Meaning you'd have to use a pull start to crank it. Still to be street legal in my state Tennessee I'd have to stay under 50cc.

 

[JerboaJohn]

I'm just thinking most of the 4T's would output too much torque on shifting for it to last unless babied. that's why shift kits for the CG's are way more popular they spin fast but don't really pound the cassettes

 

[Sidewinder Jerry]

I'm just thinking most of the 4T's would output too much torque on shifting for it to last unless babied. that's why shift kits for the CG's are way more popular they spin fast but don't really pound the cassettes

I use a Staton Inc system and SI double freewheel shift kit. The chain transitions much smother under actual road conditions. However due to the chain traveling over cogs There is chain and cog wear over time. It'd be my hope with an IGH this issue could be eliminated.