Nothing to lose really.

[DannyC]

OK, I know I said I was NOT building any more trikes. I may have been economical with the truth.
I have almost convinced myself that a 2WD delta is on my horizon and that it can be made with my 2WD unit and use that pair of cheap(ish) SA 70mm drum-hub clones I bought on flea-bay on the back wheels. I know all these things have been done before in different combinations; but not by me. So the challenge is there to be overcome.
Metal tubes/billets are on order, and the thinking cap is still on.

 

[stormbird]

OK, I know I said I was NOT building any more trikes. I may have been economical with the truth.
I have almost convinced myself that a 2WD delta is on my horizon and that it can be made with my 2WD unit and use that pair of cheap(ish) SA 70mm drum-hub clones I bought on flea-bay on the back wheels.

First problem is how to drive a SA drum brake ?

I know all these things have been done before in different combinations; but not by me. So the challenge is there to be overcome.

Be careful should you be successful there may be a ' which trike do I keep ' decision in the future ?

Metal tubes/billets are on order, and the thinking cap is still on.

Before you finalise on a frame construction , consider I am thinking of a perimeter frame to make it easier to mount a body and achieve 2wd however both sides may not come from one length of 40mmx20mm 1.5mm and so have just splurged over £74 on 2 x 3m lengths !

..and also might as well have suspension , only a couple more parts and weight

Lets see some drawings ?

Paul

 

[Popshot]

First problem is how to drive a SA drum brake ?

An interesting challenge indeed. The backplate would need fixing to the chassis and the axle passed through it on bearings and then fastened to the drum. A tough job.

 

[DannyC]

First problem is how to drive a SA drum brake ?

I think I have an idea on this.
The backplate will be affixed to an end plate on an axle-tube (4 holes drilled through the backplate and bolts into the end plate on the axle tube).
There will be a 12mm drive shaft that is supported on 28x12x8 bearings in that tube. The axle passes through the back plate and then through the drum-shell and out the other side.
A 12mm x 24TPI LH thread protrudes through the outside.
A hub "cap-plate" with the matching 12mm fine "nut" welded to it is bolted to the spokes of the hub shell, Or, the cap-plate has drive-dogs that engage with the hub shell's spokes.

There is a significant challenge to overcome in that in its natural state the hub-shell is bolted tight against the backplate and the internal separators allow the shell to spin freely on its internal bearings; this deployment requires the hub shell to be locked to the axle shaft and spin with the shaft while NOT catching on the backplate or going out of concentricity or the shell interfering on the brakes shoes.

Some trial & error testing is required, so excess M12 rod and other bits are in the plan.

This is the first bit that has to be "proved" before anything else, but I believe it can be done (famous last words).

I will make a "test" driven hub before I try to do anything else so this element will be before any firm frame plans are attempted.

 

[Popshot]

Sounds live you are making what would be described on a car as a live axle. That would preclude independant suspension.

 

[stormbird]

Maybe the whole brake assembly can be inboard and the hub not be part of the wheel ? or be driven ?

Similar to your idea with a flange that grabs the shaft and bolts to the drum , the existing bearings whilst redundant stops them having to be replaced with turned spacers.
maybe a sprocket could be introduced between the flange and the drum itself ? Of course being SA that interface will also be hard as the spokes on the hub's I have slope from the centre of the hub to the rim.
I suspect you will need a new back-plate as most of the originals are horrid affairs if you plan on bolting them to anything , there is not a flat surface parallel to the brake shoes anywhere !
Still should keep the inner lathe-boy occupied over Xmas

Paul

 

[DannyC]

Still should keep the inner lathe-boy occupied over Xmas

...and far, far beyond I suspect.

 

[DannyC]

Sounds live you are making what would be described on a car as a live axle. That would preclude independant suspension.

Yes it would indeed. Fatter tyres then.

 

[DannyC]

I have several sample "Pivots" with the 28x12x8 bearings in them so I will use one of those to dummy-up a prototype axle-tube arrangement with one of those with a 3mm plate welded on the end to fix the SA backplate to.
As far as the backplate being curved is concerned I had thought to overcome that with domed washer sets like you have on disc brake callipers.
Not sure how I will make an M12 LH threaded nut, but I might cheat and just buy them rather than mess about internal threading.
Lots to think about for sure.

 

[stormbird]

All the SA hub's I have seem unsuitable for drilling the hub spokes for bolts to interface with an axle , they are heavily domed and the easiest part to drill is also the thinnest part.

the backs are not helpful for this plan either :-

Not much room to maneuver inside either

Paul

 

[DannyC]

Yes, it will be a challenge.... doubtless.
As I paid a low price for the hubs it won't really matter to me (or anyone else) if they get mangled.
If I find a workable/repeatable solution, that would be good and would benefit others (which would be good).
We will all have to wait and see, I think.

 

[stormbird]

yes I am sure others could be interested and find it useful , except there is only you and I using SA hub brakes me thinks ?

If you will excuse a slight hijack I am looking to get a pair of these cheaply :-

As I am questioning why we bother using single side mount hub brakes on a delta ?

The delta could just as easy have 2 of these with a single speed freewheel ? all that needs doing is the drop outs being 'adjusted' to allow the wheel to move forward to get it out and clear the chain ? I always find fixing a puncture to be easier if the wheel is in my hand rather than spinning against your tyre levering forces ?

Just my 2 pence worth

Paul

 

[Popshot]

Another 2p worth is that single sided look much nicer than having chassis either side of the wheel.

 

[DannyC]

I have thought of another problem that must be overcome if this endeavour is to succeed.
The standard deployment has the hub shell spinning on its bearings around a stationary shaft/bolt.
In this deployment we need to allow the shaft to spin and impart motion to the hub-shell while NOT creating friction on the elements it passes through.
This implies that the standard Outer and inner Washers will have to be replaced with one's with an oversized bore that does not contact the axle.
All the other elements in the stack rotate freely as they turn with the hub shell anyway. This is why prototyping will be so important.

 

[DannyC]

Further investigation shows that the cheap 70mm drum hubs I snagged on e-Bay have a different construction from my own 90mm drum hubs.
The 70's have a moulded 1-piece "All alloy" ( or probably Aluminium) backplate with 2 steel pivot pins so there can be no welding anything to them.
The 90's have a 2-piece backplate whereby the Alloy backplate has a pressed steel plate riveted to it.
However, I think I can see a way to make the backplate captive relative to the main axle-tube while allowing the drive shaft to rotate.
Also, I think I have figured out a fairly simple way how to transmit the drive to the hub shell.
One of the additional challenges is that I am trying NOT to make irrevocable changes to the standard product that would prevent reversion to normal operations.

When I have some more concrete progress there will be pictures.

 

[stormbird]

Is the title of this thread misleading ?

Nothing to lose really.

Should it be

Nothing to lose really but my sanity ?

Paul

 

[DannyC]

Is the title of this thread misleading ?

Nothing to lose really.

Should it be

Nothing to lose really but my sanity ?

Paul

Really? How kind.

 

[stormbird]

Really? How kind.

Will it not be very very hard ?

Paul

 

[DannyC]

Will it not be very very hard ?

Paul

Don't know, the early mock-up says it will be "fun", but not madness inducing. It is either doable or not-doable (by me). I shall let you all know in due course.

 

[stormbird]

Would this work ?

There is a spacer inside between the drum and the back plate , if you made yours like this the piece shown here with the studs could rotate inside the brake shoes ? The far wall of the drum nearest the centre of the wheel hub could be drilled to mate with this piece and screwed through from the 5 spoke side of the hub ?

Paul