20" wheel[s] with 70mm SA hub brakes

Seem to have a 20" wheel with a dragging SA 70mm hub brake ?

Does anyone have any unused wheels with hubs with or without back plates to give me some kit to swap over and try and diagnose/fit it ?

regards Paul

Kevin

That’s a very generous offer however...

I have a confession to make ?

The wheels I am having problems with were bought from you in the first place

IIRC they were removed from an tadpole trike that shuddered  & shimmy when braking and so were replaced and I bought the wheels from you as I intended to fit them to the rear of a Delta and so did not expect to encounter those problems ?

I had some NOS back plates and hubs not laced into wheels and am trying to combine the two.

I started a thread here about the problem ?

and continued it here :-

So one hub/backplate combination works ok with the weight of the valve making the wheel swing backwards and forwards till the valve stops at the lowest point and the other grabs and stops suddenly with the valve anywhere  ...

So today not being an engineer I did this :-

Tapped one bearing in as far as it would go , added the axle and the inner anti-crush tube then put the end of my 6" steel ruler over the end of the anti-crush tube and convinced myself that the ruler was not touching the outer race lip any of the way around ?

So made another anti-crush tube filed it to a fraction shorter than the original and convinced myself that the ruler was now touching the outer race lip all the way around ?

Bolted it up hand tight and the wheel now swung to and fro before settling hurrah I here you shout ?

So I set about making these permanent [ from the point of view of being able to ride it ] and added washers and 12mm lock-nuts to the 12mm bolt axles.

Ok now I am really pi**ed off even tightening the lock-nuts till the washers were only just gripped NEITHER wheel now swings to and fro before stopping they both stop rather suddenly !!!

So wasted all this time for absolutely no improvement at all ?

regards Paul

A few key facts regarding the SA70 drums provided as service notes  by ICE

 ( I'am a UK Premier ICE Trike Dealer and have the factory approved and designed measuring tooling )

Pulsing Sturmey Archer Drum Brake Correction
 
If you have a drum brake trike which pulses when riding the trike at a low speed when one brake is applied then it is likely that the drum shell is oval.
 
In measuring drum shells it is our experience that all shells are oval to a certain degree and work fine provided that the total ovality does not exceeded approximately 0.07mm. Above 0.07mm the pulsing becomes gradually more noticeable and a wheel with ovality of  0.15mm would feel completely unacceptable.
 
Some of this ovality is due to manufacturing tolerances of the hub shell (there is actually a tolerance of  0.15mm according the S.A. drawings!) and some is due to distortion of the hub shell due to spoke tension. It is surprisingly easy to effect the ovality by small changes to the spoke tension.

Have a close look at a spares kit offered by ICELETTA of Germany 

You should spot a pair of HARD metal "spacers " the modern versions have a rebate to assist location into the back plate .

https://shop.icletta.com/en/wheels-hubs-rims-mudguards/sturmey-archer-drum-brake-complete-set.html

 Earlier versions also used by ICE during their custom built period have a slight cone but no rebate .

So can be fitted the wrong way causing a great nashing of teeth and the brakes don't like it either .

Your hit and miss pull your hair out and scratch your head method is probably forcing the drum too far onto the backplate …….hence the wheel does not want to revolve ? 

You also risk damaging the bearing seals if the home made spacers used are thin wall tubing .

Practical Cycles sell a variety of genuine SA spacers for 99p each plus PP 

Fitted correctly it should work and well worth the cost before you write off the wheels .

ICE are selling a pair of brand new but old stock axles and nylocs for £5 inc vat via EBAY 

Hope that helps with probably a simple solution to your woes ……..Kevin D 

You could consider not using the current Quick release axle fittings ?

The back plates your attempting to use are for wheelchairs .

SA do not expect WC users to hit speeds above 10mph !"£$

However if you settled for a "solid" bolt on thru axle system with the SA spacer 

You would resolve your current problems .

The ICE axles on Ebay would be perfect and of course tested as "fit for purpose" .

You would not want your wheels passing you by on the next hill because you fitted a gash bolt .

So for £10 out of your piggy bank …...you could complete the "Wheelie" parts of your project .

If you need Quick release solid thru- bolt axles ICE offer them for £26 a pair ( I have them in stock) 

Hear from you later on Tuesday and I can explain the finer points  

Regards Kevin D