Commando rear wheel in Slimline F'bed

Hi gents,

I'm trying to fit a Commando rear wheel (with cush drive shock absorbers) on my 1960 Dominator (slimline Featherbed) and I'm faced with a problem that I can't solve:
The wheel is not properly centered in the swinging arm (about 5 to 6 millimeters too far on the RH side).
I've tried different combinations of shims & spacers (using Commando and/or Dommie ones) but without any success.
I can't locate the brake plate and drum closer to the LH side because the brake plate is already very close to the swinging arm (about 2 millimeters gap) and it would'nt be enough to achieve the proper set up anyway.
It looks like if the spacer protruding out of the inner side of the brake drum should be shortened a bit, but I'm not sure at all that it is the answer.

I appreciate that it is not a commonly made modification, but if anyone has a clue, it would really help.

PS1: all the bearings / shims / spacers of the Commando wheel have been renewed and installed as per the Commando workshop manual. Nothing wrong on this side.
PS2: the swinging arm is OK. No problem at all to install & remove the Dommie wheel and perfect handling.

Many thanks & regards

Laurent

Hi Laurent

Do you have the original Dommie brake plate, brake drum, stub axle, and wheel hub? If so, measure and compare to Commando part, to try to determine what is pushing the wheel rightwards. If you do not have the Dommie parts, I can measure my Atlas parts (they are off the bike at this time).

I do not know the Cdo intricacies, but I think (think means I am not sure) the Cdo swing arm is wider where the axle passes than the Dommie or Atlas. If so, it would tend to shift the Cdo wheel on your swing arm.

Check that the chain is aligned coming off the gearbox to your brake plate/brake drum assembly. That is the first thing that must be put right.

Maybe someone has made this mod before and will chime in.

Slick

Hi Slick,

Many thanks for your prompt reply.

Yes, I still have the Dommie brake plate / drum / wheel etc... and hence I can measure and compare the 2 types of wheel to determine where is the difference.
A guy who had made it told me it was feasible and pretty straightforward except for some adjustments, but I don't remember which and have lost his phone details!!!

Brake plate / drum / shoes are of same dimensions. I suspect that the problem lies in the gap existing on the Commando between the drum and the hub (and necessary to allow the cush drives to do their job, whereas there is no gap between drum and hub on a Dommie).

Cheers,

L.

Hi again Slick,

Yes I have checked the chain alignment and it's OK. Which means that there is nothing wrong and nothing to change with the brake plate and drum location.
Solution should be found at the hub location level. The only one I'm thinking of currently is machining the spacer protruding out of the inner side of the drum, so that the hub (and rim) could be pushed a few millimeters further on the LH side.

But I will get in touch with that guy before!

L.

L:

Glad that chain alignment is OK.

I am fairly certain Cdo axle is longer than Atlas or Dommie, thus something must be wider in the Cdo than Dommie....wheel hub?

You say your wheel is 5-6 mm too far right. How much is the gap between Cdo wheel hub and drum? As I said, I am no Cdo expert, but I would think 1 mm would be sufficient to let the cushions do their work. If you have more gap than this, I would wonder why and whether the wheel is properly "homing" on the lugs.

I am not sure what spacer you are contemplating turning down, but it seems to me, the wheel hub to brake drum gap will be controlled by the stub axle (except if Cdo has an additional spacer between hub and stub axle not found on Dommie). On my Atlas, I have about 2 mm CLEARANCE between the stub axle and hub when the wheel is bolted up to the brake drum. Do you see any difference in the Cdo & Dommie stub axle dimensions?

We need a Cdo guy to chime in on this.

It might be helpful to put the wheel on the bench, insert the stub axle in the brake drum, then place drum on wheel lugs to determine if wheel homes on drum as one might expect.

Slick

If the wheel is off center, but the hub and brake, and chain alignment is good, then why not just move the rim over to center it? You could adjust the spoking to basically move the rim over on the hub to center it. Basically the hub and brake stay as they should, but the rim itself moves over, by loosening the spokes and pulling them up tight towards the side that you need to bridge the gap on.

Thanks to you both Slick & Wilkey.

The Drum To Hub gap is approx. 2mm. It is controlled by a spacer which fits into the drum bearing (contrary to a Featherbed where there is no drum bearing and of course no spacer). That spacer is in contact with the LH side hub bearing. It is the one that MAY have to be shortened a bit (whilst leaving enough gap for the cushes to mork properly).

I'm sure that the wheel fits nicely on the lugs and is set in place by the spacer (see above) as it should be.

But you're right Slick: if the Cdo long + short (dummy) spindles are longer than on a F'bed, it means that the swinging arm is wider.

Maybe I'll end up with off-setting the rim as Wilkey suggests, after having compared Cdo and Fbed components to understand why it is not as straightforward as expected!

L.

L

If your hub/drum gap is 2 mm, you cannot get 5-6 mm shift! Wilkey's offset may be only way.

Slick

I run my 850 Commando wheel on my Wideline the brake part that sits in the slot on the swing arm to brake plate has to be machined down to get the right space, I did mine in 1980 when I first built my Featherbed and all I did was to grind it down, I used my Commando spacers but you need to get the wheel sitting evenly in the swing arm I am running 19" wheels (Akront) and have enough room, the wheel spacers will need to be made to fit right and be spaced to make sure the chain runs straight, I did this 35 years ago now and is still running all the same spacers as well as the Commando brake plate, I think the Slimline will be the same, I have both Wideline and Slimeline Featherbeds, but still building the Slimline, but its all Dommie rear.
Its a pitty as I only just put my rear end back on my Wideline if you asked a week ago I could have taken pics as well as messurements.
Ashley

I also run my stock Commando axcles as well as my commando frontend, works perfect and the Featherbed stills handles great.

Ashley

I will take some more close up pics today, here is a look from the other side these pics were taken when I was rebuilding it just over 5 years ago.



Ashley

Commando swingarm is 8" width at the axle.

Some more pics










Hope this helps

Ashley

Thanks for the replies and pictures. Quite helpful!

I have adjusted the sort of pin which locates the brake plate on the swing arm (as you did Ashley) and checked that the sprockets alignment is correct and that the drum spins freely with its dummy axle tightened on the swing arm. So the set-up is OK on the LH side.
At this point of the story, the only way I see to get the rim centered is to have it laced with an off-set to the left. Once done, it will be easy to make the required RH spacer.

When you installed your Akront rim Ashley, was it laced with an off-set?

L.

laurentdom said:

Once done, it will be easy to make the required RH spacer.

Click to expand...

You should be able to make that spacer even without having the rim laced to have more offset.

The hub and drum and spacers (and speedo drive ?) won't be any different in any way,
they simply need to be the dimensions required to lock all the components in place along the axle,
and neatly fit within the swingarm.
In fact, you need to do this first, to be absolutely sure all the components are in the correct place, and the rim offset will then be correct.

Ashleys wheel looks to be laced so the rim is central to the hub.
But its hard to tell from pics, any offset may not be so readily visible.

Spot on Rohan!

I'll start with the wheel axle components from which I'll calculate the offset needed.

Merci beaucoup.

L.

It was laced to the Commando hub so don't know if it was off set or not it was laced from the place I brought the rims in 1980 so a long time ago, the spacers are the most important thing to go by and making sure the brake hub braket to the swing arm is better fit than nomal, but after 34 years its work with me.

Ashley

You need to be careful when measuring the offset and correcting it. If the difference between the LHS and the RHs is 6mm, you probably only have to move the rim or the hub 3mm.

I have been out to the garage and had a look and I can confirm what I said earlier. You need to use a Dommie dummy axle as the Commando one is too short and doesn't fit the swing arm correctly. The Dommie dummy axle needs to be machined to the same size as a Commando one so it fits into the brake drum, luckily the Dommie one is larger so can be done. You use the Dommie spacer on the drive side so you have the correct spacing to match the gearbox. It has to be correct using this, because it puts the brake drum in the same place as the Dommie one. You then have to use a Dommie rear wheel spindle as the thread is different on a Commando and a Dommie. You then use the Dommie wheel spacer on the other side, which is 1 inch, a Commando one is longer and won't fit.

My Commando wheel in the Featherbed frame is in the centre of the frame and the Commando rear rim is central to the hub. If you are using a Commando spacer on the drive side, I'm sure it is shorter and you will find that the wheel is too far over to the left. If you bolt up the drum with a Commando dummy axle, it will still turn freely, but to get it in the right place you need to use Dommie spacers.

If your wheel is off centre to the left, I would say it's because you are using Commando spacers, if it is over to the right it could be that the wheel isn't in the cushdrive rubbers enough. With new rubbers it is a very hard job to get them all the way in. I had to take the wheel out and stand on it with lots of grease on the rubbers to get it fully in.

L

Horrors post seems to have it all together for you.

One thing I would add: If you machine down the Dommie stub axle to fit the Cdo drum, give yourself about 0.020 - 0.030 clearance. this will allow you to center the drum on the brake shoes. do this by snugging up the stub axle nut, applying the brake, then cinching up the nut.

Slick

PS....I would use brake fluid to lubricate the rubbers when mounting the wheel onto the brake drum, grease can deteriorate the rubbers.