bsa A7 1947 wheel problem.

[codfish]

Hi, I need some help on this. Iīm restoring a A7 with interchangable wheels ( should be rigid but the old owner decided to fit a a plunger rear suspension). I had a hard time to find the right yokes since itīs a bit larger than the 1950 and so on. But now with the yokes assembled the wheels ( front and reaR)is not centered with the frame. I can only assume that the wheels should be laced withOUT  the hub centered with the rim. I am right or Iīm doing something wrong again?I supose that the brake hub is right for this model.See photos atached.
Any help very much apreciated!!!

By codfish25 at 2011-01-17

By codfish25 at 2011-01-17

[chaterlea25]

Hi codfish
I would seek advice over on the BSA A7/10 forum!

http://www.audioworld.net/BSA/forum/index.php

I have not come across interchangable wheels on a post war BSA???

HTH
John O R

[Rex]

Don't know about interchangeable wheels on BSAs, but you should lace the wheel to centralise the rim in the fork tubes.
Easy enough to do in situ, provided there's a little scope for spoke adjustment.
Another good reason why amateur rebuilders should take loads of measurements for the wheel builder,or do it himself mounted in the frame/forks where it's intended to be used.

Not sucking eggs here, but are you sure that a back wheel can be used up front on an A10? Not saying you're wrong, but it's a new one on me.

[esometisse]

the first two model years of the A7 - 1947 and 1948 - used indeed interchangeable wheels. These consisted of the well known "crinkle hub"
mated to a 7inch drum with brake shoes of 1 1/8 inch width.
I am not quite sure if there are drums for this setup of different width. If there are, that could be the cause of your problem.
If the drums are correct, work from the back wheel to get your center lines right.
You first have to establish that the chain alignment is correct because that will determine where the hub center line has to be relative to the frame when the wheel is mounted in rear position.
Then adjust the rim center accordingly by means of the spoke length. Repeat this for the other wheel and then go to the front and check if the wheels are in the correct position there, too. If not, correct it by shimming on the wheel spindle accordingly.
Hope this helps
Cheers
Andy

[esometisse]

by the way, knock your wheelbuilder over the head first of all things!!!!!
The big advantage of the crinkle hub is that you can use STRAIGHT spokes for increased strength with this construction!!!!!!!!
To use the usual spokes with the bent ends makes no sense at all!
Cheers

[Rex]

[If the drums are correct, work from the back wheel to get your center lines right.

I stand corrected over the interchangeable wheels, but I'd have to disagree with this.

The front rim should be spoked to end up centralised in the forks (note "rim" not "hub") as the forks are symetrical to the frame tube/spine. The rear hub should be fitted with perfect chain alignment, then the rear rim position spoked to also align with the frame tubing or spine. That way the front and rear rims are in-line with each other and the frame centre line.

To leave the front until last risks the front wheel ending up not central in the forks, and how crap would that be?

[wetdog]

I take it that what ever the ofset in relation to the front hub ends up being , the rear is the same or the intercangeable aspect is lost ? this may prove a problem if the correct position is not centeral to the hub as front to back and V/V requires rotateing the wheel 180 deg ( does that make sence )    the rear wheel needs to center  with the frame spine reguardles of chain alignment  ( as this is easyer to correct ) do both wheels need to be ofset  the same way ? did BSA fit the drums on the same side ? ( unlikely i know but not sure )

[esometisse]

@Rex:
What you say about the rear wheel makes perfect sense. In fact, it's the same as I said, maybe just in better words.
But you can NOT begin with the front wheel! Of course you have to centralise the front wheel RIM to the centre line of the forks and the frame, respectively. But you can NOT do it independently from the rear wheel situation because you want to be able to use your perfectly centralised rear wheel at the front, too! That's what the idea of interchangeable wheels is all about after all.
So you start at the back and spoke both of your wheels identically so that their rims are central in the frame when your chain is aligned, and THEN you centralise your readily spoked wheels in the front forks and adjust their position via spacers or shims on the wheel spindle. Because only on the front position do you have a little latitude as to where the hub sits relative to the center line - certainely not on the rear where the position of the hub is determined by the chain line.
That`s why you have to start from the back!

[codfish]

     First of all , thanks Rex,wetdog, Andy and John for your fast answer!
So If I understand right I should first align the chain and then ajust the rear rim to the center of the frame and then put the front wheel at the rear and ajust the rim too.After that I should put the front wheel at the front and ajust it with shims to make it centered to the frame.
     Andy there isnīt any straight spokes  in Brasil but I will buy some from Uk to to make it right!
In my ignorance I thought the BSA A7 1947 wheels were assembled with the rim centered to the hub but I think even if I change that It will be "possible" to interchange the wheels as the rear brake drum  is it the oposite side.(180 deg).
     This motorcycle came to me almost burnt and in pieces to me so I had to start from scratch.Fortunately I got a lot of help from you felow bikers which do not  have any problem in sharing information and a provision to answer my questions.
Thank you.
Antonio

[esometisse]

Yes, Antonio. That's the way I would do it anyway. And don't worry too much about the straight spokes; it doesnt matter all that much!
You did a very fine job so far and I am sure you will finish this restoration to your satisfaction.
The attached pic shows a crinkle hub with straight spokes.
All the Best
Andy

[R]

In this part of the world, all spokes start out straight - I've watched a wheel builder neatly bend them all to the required angles - on a jig.

[cardan]

Just a note of caution if you decide to centre the rims between your fork legs with the hubs as they are now.

The spoke flanges of the hubs are quite close together (i.e. narrow hub), so as you adjust the spokes to move the rim over towards the brake drum, the spokes on that side will reduce in angle - i.e. they will move closer to the plane of the rim. You need to take special note of the spoke tension if you are to retain the lateral strength of the wheel. The tension of the spokes on the brake drum side will need to be higher than those on the other side. Just how much higher depends on the difference between the spoke angles on the two sides. For example if the spokes on the brake drum side make only half the angle with the plane of the rim as the spokes on the other side, the tension of the spokes on the brake side needs to be about twice as great as those on the other side. When truing the rim laterally, this means that you if you slacken/tighten a brake side spoke by half a turn, you need to tighten/slacken its partner on the other side by only a quarter of a turn. (If you're adjusting radial run-out on the rim, it's still about 1:1 - all in the sines and cosines!)

Anyway, beware of moving the rim so far that the spokes on the brake side loose their "dish" (rim centre nears the flange on the brake side of the hub). Your wheel may collapse if give it a decent whack on the side! If in doubt, discuss with a professional wheel builder.

Leon

[Rex]

. But you can NOT do it independently from the rear wheel situation because you want to be able to use your perfectly centralised rear wheel at the front, too! That's what the idea of interchangeable wheels is all about after all.

Well, yes, but I was rather ignoring the interchangeable wheel aspect as
a) riders tend to use use-specific tyres now (ie front or back fitment) rather than some sort of universal thing as was popular back in the hard-up 1940s. Probably a useful feature if the bike (and most likely, a side car) was your year-around transport, but not something anyone's really going to utilise now, I'd say, and
b) so many bikes after 60+ years have had incorrect replacement parts fitted; hubs, spacers, even complete wheels and forks may have been changed, so unless the builder is 100% sure that it's all as BSA made it, then it's better to start from scratch and treat each wheel individually,  in  my opinion.

Anyway, if you know it's all correct, why not then just build two "front fork centralised" wheels? Wouldn't that be the most convenient way?
Mind you, I personally wouldn't do that....

[codfish]

hey Andy, it seems that your hub has a "cover" oposite of the brake, is it patern? both of my hubs dont have it , if itīs patern I will look for it as I always tought it should have a cover or something. Thanks for the incentive.
R, in Brasil all we can get made here are bented spokes for japaneeses.
Cardan, thanks for your advice, I will tell that for my wheel builder.
Rex, I agree with you, I donīt have the intention to exchange the wheels.
Thanks for all of you!!!

[esometisse]

Antonio,
I don't know if anyone sells this little hub cover as a pattern part.
But it should be easy enough to make one yourself from a piece of sheet metal or you could even turn one from aluminium.
That should be nice looking when polished!
Cheers,
Andy