1934 500 Blue Star W34-9 rear brake operating rod diameter

[David Samways]

Hello all, I'm getting dangerously close to finishing the Blue Star but it's currently fitted with a 1/4" diameter rear brake operating rod which seems a little thin. The operating lever through hole is clearance for 5/16" which compounds my doubt about the current rod.

[Bicycle repair man]

Mine is 5/16 but is a 1935 and a left hand brake drum.

[David Samways]

Thanks for the reply BRM. I notice that there's a single part number for the adjusting nut for all the 1934 lightweight machines and another for the heavier models. It's unlikely that the lightweights would use a 3/16" rod, so if 1/4" is the diameter this suggests a 5/16" for the heavier models.

[Bicycle repair man]

Does the pin on the brake plate lever rotate on yours or is it fixed?
If fixed, it will require a larger hole to allow for the rotation of the lever.

[David Samways]

Good point BRM - I'll check.

[David Samways]

The pin in the operating arm is fixed so I'm guessing 1/4" is the correct diameter. Thinking further this does make sense, the front operating rod is only 3/16" so the lightweight models may have used 3/16" rods for the rear brake.

[Steve.S]

Well David, I wonder if I might have part of the answer to your conundrum?
I am certain that the lightweight models have a 1/4" brake rod.
The Sloper models had a 3/8" diameter rod, reduced to 5/16" at the threaded end.
Since the part number for the wing nut (15-7985) is the same for the Sloper and the W35-8 Blue Star, it seems safe to assume that the threaded end of the Blue Star rod is 5/16". ( Sorry, I can't remember if yours is 34 or 35).
In the Sloper parts book, the reduced diameter is very clearly shown, but I only have a BMS photocopy of the 1935 parts book, so the picture is indistinct, but it does look as though it might have a reduced diameter. If you can get hold of an original parts book, it might show up more clearly. If so, your rod should be 3/8". To give the necessary clearance, the hole in your pin should be about 11/32". If it's smaller than this, you may have the wrong lever. There are levers with different size holes.
Hope this helps.

[David Samways]

Thanks Steve, all that makes perfect sense. I do have pdf parts books for 34, 35 and 36, but it's not clear if the diameters are reduced. It could well be that the operating lever is from a light weight. I'll do some more investigating.

David

[Bicycle repair man]

Have you got the collar that sits on the fixed pin of the rear brake arm,  collar part number 15-7975? The cross hole on this is the brake rod diameter. The collar is also used on the M20.

[David Samways]

Ah, I wondered what 15-7975 was for. I don't have it, but 5/16" passes through the operating lever pin with clearance to allow for movement. I shall make a collar to suit.

[David Samways]

What material is 15-7975 made out of BRM? I'm guessing it's steel.

David

[Bicycle repair man]

Yes , steel. There is a 1/4 bsf (or bscy, I'm not getting into that discussion!) threaded hole at the top for a grease nipple.

[David Samways]

Great, thanks again.

David

[David Samways]

Rod, bush and wingnut complete. Not sure how authentic they look, but better than what I had before.

[Bicycle repair man]

I don't think that you will have the "brake rod" police chasing you!