S1 Brake Pictures

[Alan Cun]

Hello All, Looking for some clear pics of the S1 brake caliper for S1 or RA. I would like to able to achieve as near as possible the right shape. I have the rear brake assembly consisting of an alloy backing plate same shape as the front disc. The drum is a 6 inch bronze detached from the hub and fixed to the right frame leg. A cross on the hub side of the drum must fit an adaptor between the drum and hub. To our newer forum members the S1 is a 500cc ohv early 20s. First 500cc to exceed 100mph at Brooklands. Has a hamburger set up for crankcases, that is 3 layers on top of each other. Same idea as 4 HP no sump, and mounting on two lower frame rails The gearbox mounts under the frame unlike the 4hp which mounts on the 45 angle back of motor above a single frame rail. Both gear boxes have the same internals and clutch mechanisms. An S2 750cc was also produced. Will take some pics to post showing some unusual differences from other models. regards Al

Ah Ha a walk to the shed has revealed the RA is different. Finger type grooves in the caliper and one on the rear wheel too. Still looking for a closer up look of the S1 caliper.

[Doug]

Alan,

There was an S1 that showed up at the 2007 Bristol Cavalcade. These are the pictures that I have showing the front brake-





-Doug

[Dave]

Alan sent in these photos.

[Alan Cun]

Thanks Dave for posting the pics. The first shows the inside of the rear brake. If the hub pictured is an S1 then there must have been an adaptor between the hub and drum. The hub I assume is S1 and I assume would have a hollow spindle with loose balls similar to the TS axle set up. The forks would not be wide enough to take an adaptor so I assume the hub locked into the disc. Had to show a pic of the Footboard I found with the original wrecked frame. Is this the longest footboard on a Douglas around 2 foot. I have half the other side but will cast another. Hard to see but also there is the cast alloy tool box minus lid. It fits where the carrier would normally be. Regards Al

[cardan]

What a fascinating thread. I'd better admit to being far-from-expert about Douglases, but personally I find the S1 the most attractive of the Douglas models. Let me add what little I know.

Cyril Pullin was a most intersting chap, having won the 1914 TT on a Rudge. I'm lucky enough to have an 1914 TT Rudge, and riding it I can see how it could win a race or two. It is said that as well as riding the Rudge, Pullin was responsible for the design of its frame and detail improvements to the engine. I understand that Pullin's involvement with the 100-mph 500cc Douglas was along the same lines - rider and development engineer. Interestingly Pullin went on to make significant contributions to the design of helicopters before the second war. If anyone's interested, look up his published patents!

Anyway, the Rudge/Pullin link explains why I can provide the attached press cuttings of the "S1" Douglas.

Re the brake: Doug's photos are the first time I have seen this form of disk (metal disk, metal caliper lined with friction material). Was this a Research Association (RA) design? Isn't the "usual" RA design a plain metal caliper pressing on a disk made entirely from friction material?

Re the bike: How about some nice photos of the whole S1 (either the model photographed by Doug, or Alan's project) for the "Photo guide to Douglas models" page? Feel free to move any of my photos over there.

Cheers

Leon

[roy]

There is a photo of a S1 in the Bristol Centenary Cavalcade topic.

[Doug]

Re the brake: Doug's photos are the first time I have seen this form of disk (metal disk, metal caliper lined with friction material). Was this a Research Association (RA) design? Isn't the "usual" RA design a plain metal caliper pressing on a disk made entirely from friction material?

Yes, the RA was a similar idea, but with a ferrodo disk and cast aluminum shoe as you noted. 

-Doug

[Alan Cun]

Actually Leon, that is not a thread I put the hub on the end of a tap handle with the other end in the eye of the fork, hoping to show the tips of the forks. Unfortunately the sun at that time of the day created a dark background and I didnt achieve what I wanted. The tips of the forks are holes with no gaps at the bottom, as is the rear of the frame the axle goes through an oval slot. No open section at rear.  I do have copies of the S1 parts book but the quality is very poor. Yes the S1 is a pretty bike. As Howard once remarked, mine came from a tip in Sydney and was advertised in the Trading Post. It also consisted of a side car but although a factory frame (unlikely Douglas) the whole of the tubing???? was 1 inch solid and weighed a ton, well almost. I say this was a factory sidecar frame because I did come across another the same near Tamworth. Still have the body patterns, well the pieces, as they got twisted by the dump dozer too. The bike frame is straight now and powder coated,most plating done, new tank made, mainly just waiting for the wheels to be done, and the front brake sorted. Try and show a progress pic. Alan

[Daren W Australia]

Hi pic of S1? from ebay Ta Daren


[reformat image orientation. 27Jun21, -Doug, Admin]