Sprockets Second derailleur

[Murkle]

Hi folks, I'm a new poster, but I've read around a lot so bear with me.
Since I don't want to wear out my bicycles main cassette and derailleur, what would you think of a set of forks, attached to a rack, where I can mount a rear wheel hub, cassette, and derailleur, with a sprocket welded (or another method of attachment) to the left side of the hub, for a shift kit of sorts?

While it would be a technical adventure, I'm up for that. So instead of a regular shift kit, I use a second hub and derailleur for an in-line chain drive transmission. I haven't personally seen it done, but I know it can be. What are your thoughts?

Thank you,
Murkle

 

[FurryOnTheInside]

My thoughts are that the drawbacks of the shift kit, as I see it, don't even include wear and tear on the cassette and derailleur.
Cassette and derailleur are there to be used, anyway. Buying a second set of c&d doesn't even reduce the wear and tear it just moves it to the new c&d that you just bought.

The only drawbacks of the shift kit, IMO, are
1: Drivetrain losses.. i.e. the engine power being put through three chains instead of one, three shafts instead of two (clutch and wheel), up to five tensioner pulleys instead of one, and five sprockets instead of two.
2: Difficulty in making a system where you are in "tandem" with the engine, i.e. can pedal effectively at the same time as using the engine.

Any alternative system would, in my opinion have to address these drawbacks to be a worthwhile alternative.

 

[Murkle]

My thoughts are that the drawbacks of the shift kit, as I see it, don't even include wear and tear on the cassette and derailleur.
Cassette and derailleur are there to be used, anyway. Buying a second set of c&d doesn't even reduce the wear and tear it just moves it to the new c&d that you just bought.

The only drawbacks of the shift kit, IMO, are
1: Drivetrain losses.. i.e. the engine power being put through three chains instead of one, three shafts instead of two (clutch and wheel), up to five tensioner pulleys instead of one, and five sprockets instead of two.
2: Difficulty in making a system where you are in "tandem" with the engine, i.e. can pedal effectively at the same time as using the engine.

Any alternative system would, in my opinion have to address these drawbacks to be a worthwhile alternative.

1. Drivetrain losses: wouldn't be too much loss, I'll already have like 3 axles (not the right word) for reduction... Do you know of a good reduction setup that doesn't cost much?

2. Tandem: I would have the engine and everything else on a rack, but the final drive would be a left side spoke mounted sprocket. So human power on the right, engine on the left. This setup would also let me more easily remove the engine from the bike to make it a normal bike again. - I could also move it to another bike if I brake this one.

My main concern is just the bulk of my current idea for reduction, anything for compact is ideal, but it's a bike, I'm tryna be cheap not make a new Honda... :|

 

[FurryOnTheInside]

1. Drivetrain losses: wouldn't be too much loss, I'll already have like 3 axles (not the right word) for reduction... Do you know of a good reduction setup that doesn't cost much?

2. Tandem: I would have the engine and everything else on a rack, but the final drive would be a left side spoke mounted sprocket. So human power on the right, engine on the left. This setup would also let me more easily remove the engine from the bike to make it a normal bike again. - I could also move it to another bike if I brake this one.

My main concern is just the bulk of my current idea for reduction, anything for compact is ideal, but it's a bike, I'm tryna be cheap not make a new Honda... :|

No, I don't know of a good reduction setup because I don't even know what kind of engine you plan to use.

Yes, it does sound very bulky and heavy. All those things and the hub and derailleur need to be supported really well to prevent flex that would chew up and throw chains; and with many shafts and gears, or shafts sprockets and chains there is power loss inherent in it all.

The two popular jackshaft setups are the Z shape arrangement of the Shift Kit, and the Y shape arrangement seen on some homemade projects.
The Y shape puts engine power through only two chains.

 

[Murkle]

No, I don't know of a good reduction setup because I don't even know what kind of engine you plan to use.

Yes, it does sound very bulky and heavy. All those things and the hub and derailleur need to be supported really well to prevent flex that would chew up and throw chains; and with many shafts and gears, or shafts sprockets and chains there is power loss inherent in it all.

The two popular jackshaft setups are the Z shape arrangement of the Shift Kit, and the Y shape arrangement seen on some homemade projects.
The Y shape puts engine power through only two chains.

Yeah, thanks I'll look those up I'm planning on using a chainsaw engine, all I'd have to do is replace the sprocket to fit a bike chain. The size depends on how illegal I want it, the 'limit' here is 35cc, I've got that, and I've also got a 40cc and I think a 60cc too. Since I'm not supposed to be able to shift the drive ratio anyway, I'll probably go with the 40cc. The 35 and 40 I have, have the same case so I can swap it out and look ligit. But the nice thing about the design I've thought up is that I could change out the motor without much difficulty. The reason for said complex reduction, the engine is just direct drive at the shaft.
Thanks

 

[Murkle]

Okay, so it's a bump I guess... But with ideas from other threads, I have the best reduction method: NuVinci CVT hub in a jackshaft mount!

This actually gets rid of the need for a second derailleur....

 

[5-7HEAVEN]

Yeah, thanks I'll look those up I'm planning on using a chainsaw engine, all I'd have to do is replace the sprocket to fit a bike chain. The size depends on how illegal I want it, the 'limit' here is 35cc, I've got that, and I've also got a 40cc and I think a 60cc too. Since I'm not supposed to be able to shift the drive ratio anyway, I'll probably go with the 40cc. The 35 and 40 I have, have the same case so I can swap it out and look ligit. But the nice thing about the design I've thought up is that I could change out the motor without much difficulty. The reason for said complex reduction, the engine is just direct drive at the shaft.
Thanks

With only a shift kit and a single jackshaft, you will not be able to create a low enough gear ratio to maximize the chainsaw's potential.

 

[Murkle]

Well, that's why I was talking about the reduction methods in post #3... But I'm working on a SketchUp of it...