Nothing to lose really.

[Popshot]

A thought has occurred and pleased I am that they still do.
Mobikes have a shaft driven hub on the rear. They use a disc rather than a drum but the principle of being a shaft driven hub is the same. I never took the one I have apart but suspect I'd find a one way bearing in there as a freewheel just like a tongshen mid drive. If one of a pair of those had the one way reversed they'd make an axle set with an easily connected shaft at each end. I appreciate you don't need any extra freewheeling ability if using your diff but you could use a simple solid shaft between them with the one ways acting the part of the diff. You could use the principle of a one way bearing as the drive on a Sturmey hub if you can find one to fit in that recess in the outer face. If you can't find one then perhaps you could machine it to suit or even weld a small housing to the front face to fit one. I appreciate it's not as simple as simply sticking a one way bearing in as the shaft then needs to comprehensively grip the inner part to supply drive but it's possibly an area for thought.

These rear mobike hubs could also be more easily converted to a both driven and turning axle than most other designs. All you'd need is a small plate as an upright to mount the hub with it's 5 bolts and shorten the shaft as much as practical and add a uj. No central diff needed because of the one ways. Just a shaft with a solid drive. The shaft would need a sliding part to cope with the changing length during turns. I'm starting to get ideas of a 4ws, 4wd quad with auto locking diff functions now. I need to lie down.

 

[DannyC]

A thought has occurred and pleased I am that they still do.
Mobikes have a shaft driven hub on the rear. They use a disc rather than a drum but the principle of being a shaft driven hub is the same. I never took the one I have apart but suspect I'd find a one way bearing in there as a freewheel just like a tongshen mid drive. If one of a pair of those had the one way reversed they'd make an axle set with an easily connected shaft at each end. I appreciate you don't need any extra freewheeling ability if using your diff but you could use a simple solid shaft between them with the one ways acting the part of the diff. You could use the principle of a one way bearing as the drive on a Sturmey hub if you can find one to fit in that recess in the outer face. If you can't find one then perhaps you could machine it to suit or even weld a small housing to the front face to fit one. I appreciate it's not as simple as simply sticking a one way bearing in as the shaft then needs to comprehensively grip the inner part to supply drive but it's possibly an area for thought.

These rear mobike hubs could also be more easily converted to a both driven and turning axle than most other designs. All you'd need is a small plate as an upright to mount the hub with it's 5 bolts and shorten the shaft as much as practical and add a uj. No central diff needed because of the one ways. Just a shaft with a solid drive. The shaft would need a sliding part to cope with the changing length during turns. I'm starting to get ideas of a 4ws, 4wd quad with auto locking diff functions now. I need to lie down.

Hi Popshot,
Yes, Sprag-clutch bearings would allow this and eradicate the need for a "diff" in a shared driven axle arrangement.
Every Sturmey drum hub I have ever taken apart all have 28 x 12 x 8mm bearings. So to make this work you would need to have the sprag-clutch bearings with both internal AND external keyways.
This might be doable, but, that size of bearing has a very low Newton-Metre (foot-Pound) load capacity. At least I have not found any with a sufficient load rating for hill starts with a loaded trike + rider.
Maybe I need to look harder?

 

[Popshot]

The TSDZ2 bearing is keyed only internally. It relies on a friction fit to the outer. Maybe you could put two bearings side by side in that outer drum to share the load. It looks like you could press an extra one in at least most of the way. Also don't forget that each wheel is only passing half any load to it's bearing(s) unlike the Tongshen which takes all the load. Even if hillstarting at an angle and the inner slips because it can't take it it will only slip until the outer wheel is caught up to at which point both then are then driven again so in all situations it will distribute all force across both wheels. If you could double up on them then each one is taking only a quarter the load.

TSDZ2 unit.

 

[DannyC]

The TSDZ2 bearing is keyed only internally. It relies on a friction fit to the outer. Maybe you could put two bearings side by side in that outer drum to share the load. It looks like you could press an extra one in at least most of the way. Also don't forget that each wheel is only passing half any load to it's bearing(s) unlike the Tongshen which takes all the load. Even if hillstarting at an angle and the inner slips because it can't take it it will only slip until the outer wheel is caught up to at which point both then are then driven again so in all situations it will distribute all force across both wheels. If you could double up on them then each one is taking only a quarter the load.

TSDZ2 unit.

True on the load distribution, and the outers could be "glued" in with bearing glue beyond their "friction-fit" limit.
Smallest I have found is a 32x12x10 so some machining would still be required in each hub and then they are not able to be returned to standard.
But it is a good option nevertheless.

 

[DannyC]

Further to the musings above, today I made some simple parts to enable the "driven-hubs" to be attempted.

The basic concept is to create 2 half-shaft axles in tubes with the 2WD unit in the middle.
The 2 half-shaft units will be welded into a carrier framework for alignment purposes.
The outer ends of the half-shafts will be threaded to take drive-dogs.
RH half shaft will be LH threaded, LH half-shaft will be RH threaded.
Instead of inner and outer race separators there will be some machined "bearing retainers" that will be puddle-welded into position.

The layout may be like this.

I think it will work.

 

[DannyC]

Doh! I just realised that my bearing retaining bush idea will not do what I want it to do because I must have the inner race able to rotate with the axle.
So, a minor change, the retaining bushes will have their centres drilled out to 17mm in order to clear the inner race. I looked at a video of a Hase bearing replacement and they appear to only have the outer race held in a clamp and they don't appear to worry about side-loads; so neither shall I.

Another consideration is how to lock the axle-shaft to the output of the 2WD unit. It is a 12mm rod in a 12mm hole, so I was thinking either an M6 SS bolt or a hardened roll-pin.
What do you think is best guys?

 

[Popshot]

I would think a roll pin will hold it tighter than a bolt. The pin will expand to grip the hole but the bolt will not. Also a pin will be perfectly balanced but again a bolt will not.

If you have room you could weld one half of a double split clamp to the outer face of the hole. The other half will then be free to grip it. I doubt any of us could generate enough power to break that clamping force.

 

[stormbird]

Doh! I just realised that my bearing retaining bush idea will not do what I want it to do because I must have the inner race able to rotate with the axle.
So, a minor change, the retaining bushes will have their centres drilled out to 17mm in order to clear the inner race. I looked at a video of a Hase bearing replacement and they appear to only have the outer race held in a clamp and they don't appear to worry about side-loads; so neither shall I.

Way over my head , however maybe it doesn't matter ?

Another consideration is how to lock the axle-shaft to the output of the 2WD unit. It is a 12mm rod in a 12mm hole, so I was thinking either an M6 SS bolt or a hardened roll-pin.
What do you think is best guys?

On building this I suspect [ well least if I was building it ] this locking device needs to be very easy to remove as during construction it will be in and out many times ?
Also will it have to be removed for any maintenance jobs after completion ?
So my money is on a M6 bolt ?
Paul

 

[Popshot]

I'd certainly use a bolt during construction for the reason you mention but without any clamping or spline system the bolt or pin is then the sole means of drive. I'd worry that the looser the joint to start with then the more movement is possible and the more friction and wear can occur. Could it be welded in or is some movement perhaps beneficial to allow for minor misalignment in which case a bolt becomes preferable?

 

[DannyC]

Thanks both. I shall think on this some more.

 

[DannyC]

Some progress today.
I tinkered with some tube so that 28x12x8mm bearing would fit inside it.

Then I worked on the axle half-shafts so that the bearings would in fact be a slip-fit and not jam up on the metal bar. This means the half-shafts will be removable and bearings can be replaced as needed.

 

[stormbird]

DannyC

A nice day for tinkering in the garage , did the shaft take long to emery smaller ?

Paul

 

[DannyC]

DannyC

A nice day for tinkering in the garage , did the shaft take long to emery smaller ?

Paul

Hi Paul,
No it was surprisingly quick once mounted in position.
An emery band, some cutting oil and 600 RPM made pretty short work of it.

 

[pegasus]

When I bought my reasonable priced lath, one criteria was that the through hole was more than 19mm.
The one I bought has a 22 mm through hole, but when I wanted to alter my 19mm axle I realised the chucks center hole is only 18mm, grrr.

 

[DannyC]

When I bought my reasonable priced lath, one criteria was that the through hole was more than 19mm.
The one I bought has a 22 mm through hole, but when I wanted to alter my 19mm axle I realised the chucks center hole is only 18mm, grrr.

Mine has a spindle bore of 25mm I think, I too wish I had opted for one of a larger bore (34mm) but we have what we have.
I have had a lot of fun and learning with it no matter the deficiencies.
I would love to get a bigger machine...but.... space is limited.

 

[DannyC]

I did a little bit more today and put a Left-Hand M12 Fine thread on the end of the Right-Hand axle.

Nothing fancy just used a die holder in the tailstock and turned the headstock by hand.
I made a schoolboy error and scored up the shaft in the headstock jaws, but I polished the score marks out again and the bearing is still a slip-fit along the axle.

 

[stormbird]

I did a little bit more today and put a Left-Hand M12 Fine thread on the end of the Right-Hand axle.

Nice

I made a schoolboy error and scored up the shaft in the headstock jaws, but I polished the score marks out again and the bearing is still a slip-fit along the axle.

Is there a non schoolboy way of doing it then ?

Paul

 

[DannyC]

Is there a non schoolboy way of doing it then ?

Yes. Stupidly I had not realised that the rod I wad threading had hit the back of the die-holder and was too wide to fit through the hole in the back, so the thread stopped and the bar was forced to rotate in the headstock.
Silly mistake, and I put a few more thread-turns on with a standard die holder instead.

 

[maddox]

Spindle bore on my HBM lathe, the whopping 39mm.
Had a lot of use of that in the past. Machining go cart shafts (30mm) and such.

 

[Popshot]

I'm getting an inferiority complex at 12mm with my md65.