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Author Topic: Frame strut (brace) Rubber Cow  (Read 401 times)

Offline dogshome

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Frame strut (brace) Rubber Cow
« on: October 22, 2021, 04:05:13 PM »
I spotted a particularly nasty set of frame braces on the web. Two exhaust U clamps welded to a bit of tube. E149, so priced OK, but not pretty. A nice looking equivalent with threaded ends and what look like simple rose joints are going for nearly E400. So I am making a home brew.

It stands me 20 for 4off 28mm pit bike handlebar clamps, some 3/4" 16SWG tubing and 4 round M12 threaded long nuts. The rear frame tubes are 28mm and the front are 32mm. More pics to come.
« Last Edit: October 25, 2021, 02:10:56 PM by dogshome »
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Online wilcom

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Re: Frame strut (brace)
« Reply #1 on: October 24, 2021, 12:19:16 PM »
I'll be watching this thread with interest...... let us know if it makes a difference you can feel.

I don't know about my bike but I think I could use a couple of struts. :naughty:
Joe Wilkerson
Telephone man with a splash of Data
Menifee, CA

Present:
1984 BMW R65LS "Herr Head"
1982 BMW R65LS 
past:
1979 R65
1980 R65
1982 R80RT
1974 R90/6
1972 R75
1964 R50/2
19xx R27
ZX-11

Offline dogshome

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Re: Frame strut (brace)
« Reply #2 on: October 24, 2021, 01:33:44 PM »
I will. The fork brace made a surprising difference. Passing lorries on the motorway gives no wobbles. Then again, i have replaced wheel bearings and adjusted the swingarm ones, making incremental changes also.

Looking at the frame, it's two rectangles only joined together at the bottom by the engine bolts. Tying the gearbox to the top tube looks the most secure, but I'm not messing the bike up for that. The back end where the subframe bolts also looks wibbly. These side braces should link the headstock to the swingarm and will triangulate the two big rectangles. Exactly how much impact that makes I really don't know. I do know that the oversized 'aerospace' pushbike racer I had with hand brazed joints was a lot stiffer than the Reynolds 531 "pipe-fitting" frame before it. The conventional frame bike would weave going downhill at 50MPH and cause the chain to hit the front derailleur going uphill, whereas the the hand made frame was a lot nicer to ride.

I will be putting some bends in these side braces and should be able to stick weld by cutting access holes to the long nuts through the tube. Fill the hole, grind it down.

The bike was 1 person power, so even a relatively meagre 60 or 70 horse power must be deflecting the simple BMW frame. I was thinking of getting the rear frame off to powder coat it and can see an ideal place to put a cross brace between battery and rear mudguard. The subframe is a simple hoop with no side to side support. Where does the twist from my weight and the push from the shocks go? The idea with both these braces is that I don't have to remove good things like the air filter or mess up simple battery maintenance or make it look unusual etc. My mate has a TIG welder, so I'm hoping if I get everything cut and tacked using my stick welder on the subframe, he can do a much better job than I will to finish it.

The R65 front forks are only 31mm, but the top and bottom clamps are thick aluminium. I could not believe the steel thing on some of the bigger bikes! Looks really wibbly. So no plans there.
« Last Edit: October 24, 2021, 01:43:37 PM by dogshome »
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline Burt

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Re: Frame strut (brace)
« Reply #3 on: October 24, 2021, 08:16:29 PM »
Not sure if I am on the right track here but are you attempting to stiffen up the chassis to get around the the "rubber cow" reputation of the frame? 

If so, I recall an article in one of the US magazines years ago when someone welded a brace underneath the rear swingarm in an attempt to stiffen things up.  There is a chance I may have a copy of that article somewhere but will have to have a good look in amongst all my old BMW stuff. 
Black 1984 R65 - the Wombat

Offline dogshome

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Re: Frame strut (brace)
« Reply #4 on: October 25, 2021, 04:07:12 AM »
That is the plan. I don't go racing or ride fast, but do appreciate something I can hang-off on country roads and that won't get in a shimmy from a pothole mid-corner. I remember the CX500 was really bad for that. The frame on my H100 also flexed around corners, but was light and could be levered where you wanted with the wide bars.

The R65 is stable with the right tyre pressures and front fork brace and not in the rubber cow category. I rode numerous 70s and early 80s bikes and lots of those were  :cowsleep:
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline dogshome

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Re: Frame strut (brace)
« Reply #5 on: October 25, 2021, 11:57:00 AM »
Plan A. The bit of copper I had laying around is easier to add or subtract bend to get the shape. The 16SWG steel I only want to bend once! There is a good 20mm clearance between everything and everything else and it does not stick outboard of the frame.
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline dogshome

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Re: Frame strut (brace)
« Reply #6 on: October 25, 2021, 01:54:49 PM »
ideas:

Pic 1 is of the notorious H1 Widow-maker. I have ridden one of those and a tuned up H2 which was very scary even with wide bars to get hold of it! H1 had clippons and was nasty.
Pic 2 is of the (not dissimilar) BMW frame. At least the headstock is tied to something substantial and not just a cross piece. The wide open spaces between headstock and swingarm are obvious. Also square and not triangular.
Pic 3 Norton frame. Closed spaces and frames tied together at front. Upper shock mounts tied into the frame and not out in the subframe.
Pic 4 red lines are the braces I can fit easily, with green lines being the forces I am expecting to deal with. Black represents the engine.

X braces on the down tubes at the front and above the swingarm pivot are obviously better, but the engine sticks out at the front and the battery and airbox are at the rear. COMPROMISE: The side bars fit easily and the subframe (which needs paint) comes off for welding.
 
« Last Edit: October 25, 2021, 02:05:35 PM by dogshome »
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline Burt

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Re: Frame strut (brace) Rubber Cow
« Reply #7 on: October 26, 2021, 05:19:15 AM »
I like the idea.  I know I have seen something very similar in the past as an accessory but unsure which model it was for.  Possibly from Luftmeister?

I've had the bump in the long sweeping corner on my '65 in the past well above the speed limit and the wobble was put it politely a little un-nerving. 
Black 1984 R65 - the Wombat

Offline dogshome

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Re: Frame strut (brace) Rubber Cow
« Reply #8 on: October 27, 2021, 12:30:32 PM »
3 or 4 plug welds either end and paint now.
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline dogshome

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Re: Frame strut (brace) Rubber Cow
« Reply #9 on: November 02, 2021, 02:02:14 PM »
I'm not sure about my friend's welding. What do you think?  :-\
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline dogshome

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Re: Frame strut (brace) Rubber Cow
« Reply #10 on: November 02, 2021, 02:05:46 PM »
 8) 8) 8) 8) 8) ;D
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline Justin B.

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Re: Frame strut (brace) Rubber Cow
« Reply #11 on: November 03, 2021, 09:14:00 PM »
Good looking spot welds.
Justin B.

2004 BMW R1150RT
1981 R100RT - Summer bike, NEKKID!!!

Offline dogshome

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Re: Frame strut (brace) Rubber Cow
« Reply #12 on: November 14, 2021, 09:36:11 AM »
One brace is on, the other is proving troublesome. There is less wriggle room on the right due to the cylinder being close to the frame at the rear. Combined with the speedo cable and airbox inlet this side, I can't get enough room to drop it in. Without the RT frame strut there would be enough height. It's frustratingly 'not quite'  >:( It went before the nuts were welded in, but that wriggle has now gone.

I've been out with one brace on today and it's doing something. Much like a tyre pressure check and finding the front is a couple PSI low - maybe, not sure. What is noticeable though is the change in engine vibration. The horn did flap occasionally and the plastic sheet that moves with the bars on the RT did it regularly. Both of those have shut up. It's all marginal stuff, but something is going on.

I have a cunning plan for the RHS, the problem being my brace needs a good 15mm of drop-in clearance and can't be adjusted once in.

Nice sunny day pic (brace side).
« Last Edit: November 14, 2021, 12:14:25 PM by dogshome »
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline dogshome

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Re: Frame strut (brace) Rubber Cow
« Reply #13 on: November 14, 2021, 12:00:41 PM »
I had to borrow Mr Millyard's hacksaw for this. Mine is nowhere near accurate enough  ;D
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline Tony Smith

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Re: Frame strut (brace) Rubber Cow
« Reply #14 on: November 16, 2021, 01:12:51 AM »
Fork Brace - yes you will defintely feel the difference. Fork braces are good.

Frame brace - unless you are Valentino Rossi in mufti you will not feel the difference.
1978 R100RS| 1981 R100RS (JPS) | 1984 R65 | 1992 KLE500 | 2002 R1150GSA |