MattyCiii
100 kW
Thread resurrection.
In the 3 years since I started this thread I've made some design changes. I'll document them all later, but here's at least one detail: I'm going to mix RC drive electric power with human power using a jackshaft, behind the cranks and concentric with the rear suspension pivot.
Picture if you will: the jackshaft will double as the suspension pivot. Using a freewheel, electric power will be put to the shaft on the left side of the bike. Also using a freewheel, human power will be put to the jackshaft on the right. A cog fixed to the shaft will send human and/or electric power to the rear wheel via a chain...
Believe me it all seems to work in my imagination!
So, using as many off the shelf parts as possible - especially parts that wear such as cogs and freewheels - I'm designing a freewheel/cog mount for the 1/2" jackshaft.
Below: a 1/2" shaft. Placed loosely on it, a Shaimano 9-splined adapter (for human input to a NuVinci hub, used here for example). Below that, a freewheel adapter from user Recumpense: thread on a 30mm freewheel, two set screws fix the adapter to the 1/2" shaft...
Here's a picture of the Recumpense freewheel adapter showing its set screws. Note: this is a 1.375" freewheel on a 30mm mount, so it's just haphazardly friction fit. That's why it's crooked in the picture!:
I don't have a lot of space to work with so things have to be mashed together. The mounted cog and freewheel will look a lot like this:
Here's the part I have in mind: half of it is a 1.375-24 threaded section for a screw-on BMX freewheel, the other half has two 90 degree offset set screws to fix the adapter to the shaft. Once the adapter is affixed to the shaft the fixed cog slips over the splines and is held in place with a big "C" shaped spring clamp. Here's the problems this solves:
1. After awhile, freewheels are very hard to remove, because putting power to through them makes them thread on tighter.
2. So to remove a freewheel from an adapter, in the past I've had to put the adapter in a vice to unscrew the freewheel. In the future I hope to use a chain whip to hold the cog in place to remove the freewheel
3. Worst case, it'll always be easy to remove the cog and loosen the set screws to take the adapter off the shaft so I can work on it off of the bike...
Here's the cog. It has a 9 spline interface that would work with a Shimano cassette interface. The NuVinci N360, 380 etc use these cogs.
This is a NuVinci freewheel with the cog placed on it. It's a wear part (should the bearing fail or freewheel pawls wear), inexpensive and replaceable. I'm using it because it looks like what I need...
Here it is with the ring clip in place, keeping things nice and tight:
Why am I bringing all this up? I'm going to have some of these parts made. I got a quote from eMachineShop.com for $40 per adapter, as long as I buy 10. They're about $150 each if I buy 2 (I need 2 for my next bike).
Interestingly, a much simpler part - one that simply has 1.375-24 thread the whole length (because I could simply just use a thread-on cog) costs almost the same amount...
So I'll write a new post with some specific machinability questions to the machinists out there sometime this weekend. Stay tuned!!
8296
In the 3 years since I started this thread I've made some design changes. I'll document them all later, but here's at least one detail: I'm going to mix RC drive electric power with human power using a jackshaft, behind the cranks and concentric with the rear suspension pivot.
Picture if you will: the jackshaft will double as the suspension pivot. Using a freewheel, electric power will be put to the shaft on the left side of the bike. Also using a freewheel, human power will be put to the jackshaft on the right. A cog fixed to the shaft will send human and/or electric power to the rear wheel via a chain...
Believe me it all seems to work in my imagination!
So, using as many off the shelf parts as possible - especially parts that wear such as cogs and freewheels - I'm designing a freewheel/cog mount for the 1/2" jackshaft.
Below: a 1/2" shaft. Placed loosely on it, a Shaimano 9-splined adapter (for human input to a NuVinci hub, used here for example). Below that, a freewheel adapter from user Recumpense: thread on a 30mm freewheel, two set screws fix the adapter to the 1/2" shaft...
Here's a picture of the Recumpense freewheel adapter showing its set screws. Note: this is a 1.375" freewheel on a 30mm mount, so it's just haphazardly friction fit. That's why it's crooked in the picture!:
I don't have a lot of space to work with so things have to be mashed together. The mounted cog and freewheel will look a lot like this:
Here's the part I have in mind: half of it is a 1.375-24 threaded section for a screw-on BMX freewheel, the other half has two 90 degree offset set screws to fix the adapter to the shaft. Once the adapter is affixed to the shaft the fixed cog slips over the splines and is held in place with a big "C" shaped spring clamp. Here's the problems this solves:
1. After awhile, freewheels are very hard to remove, because putting power to through them makes them thread on tighter.
2. So to remove a freewheel from an adapter, in the past I've had to put the adapter in a vice to unscrew the freewheel. In the future I hope to use a chain whip to hold the cog in place to remove the freewheel
3. Worst case, it'll always be easy to remove the cog and loosen the set screws to take the adapter off the shaft so I can work on it off of the bike...
Here's the cog. It has a 9 spline interface that would work with a Shimano cassette interface. The NuVinci N360, 380 etc use these cogs.
This is a NuVinci freewheel with the cog placed on it. It's a wear part (should the bearing fail or freewheel pawls wear), inexpensive and replaceable. I'm using it because it looks like what I need...
Here it is with the ring clip in place, keeping things nice and tight:
Why am I bringing all this up? I'm going to have some of these parts made. I got a quote from eMachineShop.com for $40 per adapter, as long as I buy 10. They're about $150 each if I buy 2 (I need 2 for my next bike).
Interestingly, a much simpler part - one that simply has 1.375-24 thread the whole length (because I could simply just use a thread-on cog) costs almost the same amount...
So I'll write a new post with some specific machinability questions to the machinists out there sometime this weekend. Stay tuned!!
8296