BMW R90/6 Cafe

ncologerojr

Coast to Coast
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Next I moved on to the tail cowl. It has to house the battery, which is large due to keeping the electric start. For this I chose to make a wire form buck. Not a great pic of t, but you get the idea. Next more aluminum was shaped.

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ncologerojr

Coast to Coast
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After the cowl pieces were welded a flange was turned to add strength, a seat pan was bent and everything welded up.

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ncologerojr

Coast to Coast
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Next I started on the under-tail details. A tight fit aluminum panel with a rubber seal will make up the battery tray. It will be bolted to the frame separate from the cowl so the cowl can be lifted off the battery for servicing. Another panel creates an area between the frame tubing for wiring/components. (Not the final hardware)

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ncologerojr

Coast to Coast
DTT BOTM WINNER
trek97 said:
Bro I am right there w you. Sure I enjoy going for a ride. However, I leap out of bed in the mornings if there’s work to be done.
I am in awe of the work you and some others are doing. Sometimes I’m surprised you all allow me to be here at all.

Thanks man, there are some very talented guys on here. I’m just a hack that likes working metal.
 

ncologerojr

Coast to Coast
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Today I’m working on the battery tray. Made a quick dimple die on the late to dress things up a little.

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irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Are you going to stiffen up the cradle so it's not a rubber cow anymore? Curious if that will get even worse (or better) now that it's a mono shock. Considering where your top mount is, I don't have as high of hopes.
 

ncologerojr

Coast to Coast
DTT BOTM WINNER
irk miller said:
Are you going to stiffen up the cradle so it's not a rubber cow anymore? Curious if that will get even worse (or better) now that it's a mono shock. Considering where your top mount is, I don't have as high of hopes.

I’ll do what I can. With the original bolt-on subframe, the rear section of the frame was not tied together well and able to twist independently with the swingarm. My rear subframe ties that area together. I don’t see why my shock mount would concern you. With the rear tubes converging in that area it’s pretty supported...
 

farmer92

Coast to Coast
It would concern me as well.
With the original mounts there was zero load on the SA pivots (next to zero anyway)
The shock loads were countered by the lower subframe mounts and they look to have a load of about 1.25x the shock load.

Wit your new mono-shock mount you have greatly increased the leverage on the shock, and obviously also the forces, but this greatly increases the load on the SA pivot.
To my point
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The slight downward angle helps out a bit in reducing the forces but you are probably now putting double the wheel load into the SA pivots.
You are also forcing the top end of the cradle forwards with double the wheel load but that is less of a concern here.
 

farmer92

Coast to Coast
Also, it looks like you have a regressive rate geometry on the rear suspension.
If the shock angle changes and slowly becomes more vertical as it compresses then that is indeed the case. It’s hard to tell from the photos though.
 

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Have you ever ridden an airhead? They didn't earn their rubber cow moniker for nothing. LOL . Between the orientation of the motor/crank rotation and the featherbed-like design of the frame, they are extremely sloppy in turns. It's a very soft, noticeably rubbery effect.
 

ncologerojr

Coast to Coast
DTT BOTM WINNER
farmer92 said:
It would concern me as well.
With the original mounts there was zero load on the SA pivots (next to zero anyway)
The shock loads were countered by the lower subframe mounts and they look to have a load of about 1.25x the shock load.

irk miller said:
Have you ever ridden an airhead? They didn't earn their rubber cow moniker for nothing. LOL . Between the orientation of the motor/crank rotation and the featherbed-like design of the frame, they are extremely sloppy in turns. It's a very soft, noticeably rubbery effect.

Gotcha, I see what you guys are getting at now. The way I read Irk’s first post I thought he was talking about the top shock mount specifically failing or something, now that I re-read I see what you were saying.

Yeah, these frames are known for flex. The first thing I did was start looking at road race bikes to see how those guys deal with it. Actually, first thing I did was consider build a new frame, but it’s not in the budget. I plan to make braces like guys run on their race bikes (pic below), but I need to get everything else in place first to avoid clearance issues. I’ve been thinking over supports in the rear coming from the SA mounts and running to the top shock mount, and a cross brace at the SA mounts to triangulate the area. Similar to what’s in the picture. If you look close, you might or be able to tell in the pictures, the top shock mount isn’t completed because I am considering using it as a landing pad for the rear braces.

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B

BenHolmes21

Guest
Incredible work on this! Can’t wait to see the end result!!


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Hurco550

Keep er' Between the Ditches
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Beautiful work as always on the body work! Thanks for sharing it here. And yeah, can't argue that my R90/6 doesn't feel a bit "wet noodly" when pushing it into a turn lol

This one has an entirely custom frame (I think) but its another idea for bracing none the less.
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