Riddle me this racing aficionados

All about BMW in racing can be discussed. Sharing of pictures, and other information.
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jwonder
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Riddle me this racing aficionados

Post by jwonder »

Hello,

I was browsing around the Internet yesterday and I came upon this very strange rear end suspension configuration on a plunger frame. I am wondering if this is an "official" racing suspension or just something someone put together. I still don't fully know how it is working from the pictures but I am studying them more!
inzerce_zoom_343342.jpg
inzerce_zoom_343347.jpg
inzerce_zoom_343349.jpg
James Wonder
Long Island, New York

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schrader7032
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Re: Riddle me this racing aficionados

Post by schrader7032 »

Isn't it just a different type of shock (as in exposed coils) used on a plunger frame? The top and bottom parts of the shock are fixed. The axle comes over and connects to a moveable part of the shock that is connected to the lower coil of the spring. As the axle goes up when hitting a bump, the spring compresses.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

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caker
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Re: Riddle me this racing aficionados

Post by caker »

I'm pretty sure this is homebrewed and/or Russian, and/or cobbled together nonsense? I found the listing it came from and it's kinda a mess.

Some (early?) plunger final drive cover castings did have a cast-in boss to accept a suspension friction damper? ... I don't know too much about it - perhaps a holdover from the prewar R51 racing era, or perhaps BMW had intentions of making the damper part of production but was later abandoned...

Before I post your own pic back here as an example of the boss, you have a picture of one that you sent me a week or two ago :)

-Chris

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jwonder
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Re: Riddle me this racing aficionados

Post by jwonder »

You mean this boss.
Screen Shot 2021-02-03 at 9.47.52 PM.png
James Wonder
Long Island, New York

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caker
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Re: Riddle me this racing aficionados

Post by caker »

Ya!

Some pics I took at BMW in Munich:
2A0660EB-6542-4A72-8F2C-EEA2D6AA082D.jpeg
624A5565-E150-4F0A-83C9-FE1E7A54617C.jpeg
360EF437-D459-4643-89BE-D8369EF54764.jpeg
45F7164D-0025-470D-936F-EB970A41DDA6.jpeg
FAF32926-D1BA-4EC7-8D7C-AFD4BF6E476F.jpeg
-Chris

stwilliams
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Re: Riddle me this racing aficionados

Post by stwilliams »

The flat round area or "boss" was indeed intended for the application of a hydraulic damper on the right rear of late plunger bikes. So you may see starting around 1953. The damper was never put into production.

jwonder wrote:
Wed Feb 03, 2021 9:48 pm
You mean this boss.

Screen Shot 2021-02-03 at 9.47.52 PM.png

stwilliams
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Re: Riddle me this racing aficionados

Post by stwilliams »

As others pointed out, this is 100% conclusively NOT BMW racing product. Cobbled together and/or fabricated by previous owner. Perhaps was a sidecar at some point given some of the brackets/handles that are on there. Interesting from an ingenuity standpoint, not so much from an originality standpoint.
jwonder wrote:
Wed Feb 03, 2021 6:31 pm
Hello,

I was browsing around the Internet yesterday and I came upon this very strange rear end suspension configuration on a plunger frame. I am wondering if this is an "official" racing suspension or just something someone put together. I still don't fully know how it is working from the pictures but I am studying them more!

inzerce_zoom_343342.jpg

inzerce_zoom_343347.jpg

inzerce_zoom_343349.jpg

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jwonder
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Location: Long Island, New York
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Re: Riddle me this racing aficionados

Post by jwonder »

caker wrote:
Wed Feb 03, 2021 11:52 pm
Ya!

Some pics I took at BMW in Munich:

2A0660EB-6542-4A72-8F2C-EEA2D6AA082D.jpeg

624A5565-E150-4F0A-83C9-FE1E7A54617C.jpeg

360EF437-D459-4643-89BE-D8369EF54764.jpeg

45F7164D-0025-470D-936F-EB970A41DDA6.jpeg

FAF32926-D1BA-4EC7-8D7C-AFD4BF6E476F.jpeg

-Chris
I like that friction damper. I could build one of these fairly easily. Hmmmmm.
James Wonder
Long Island, New York

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