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Old 11-30-2011, 01:20 PM   #1
Damian_74 OP
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BMW F650 in a Diet!

Weight Saving
Have just scored another 2005 Dakar on the cheap - am thinking of going to town with the grinder and scales!!

Have any of you blokes looked into a different swing arm? I hate the adjusting system and having to run it towards the end of it's adjustment to fit in an 18" wheel - and it is very heavy!

Looked a a KTM 640 bit it was too narrow to fit on the back of the Rotax engine, the only other option that I can think is is a Husaberg (also runs the chain in the right) but from the photos that I have seen the linkage set up looks all wrong. Any one have know of any other bikes that I could steal a swing arm from?

The other option is to make my own - Had a think, made a couple of drawings, checked the aluminum stock sizes and it can be done - I have a lathe, mill and TIG!
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Old 11-30-2011, 01:38 PM   #2
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Grade Selection

There are so many to choose from!

Have done lots of looking, and I keep coming back to 6061 - easy to get hold of, highly weldable, machines, and heat treatable.

Had a chat with the foundary manager of Harob Engineering, the cost of having the swingaarm heat treated after fabrication is very low - off the top of his head he was talking about $4/ Kg - that seems very cheap but I am sure there are other costs (min charge, setup or something like that).

He also suggested having it anneled to T7 grade - have spent some time looking on the new but can't find any specifications for 6061 T7 - can anyone help here?

http://www.engineersedge.com/aluminum_tempers.htm

Damian_74 screwed with this post 07-24-2012 at 07:02 AM
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Old 11-30-2011, 03:19 PM   #3
tex_downey
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i can post as Im no longer taking over taking over the f650 thread. thanks for starting a new one.


I know it would be a pain but I have a tig and lots of time, I was womdering about just fabing one up out of AL plates. thicken it up and see how it works.

But then I wonder it it would just be easyer to get one off a G650X, I keep hearing its the short travel that caused them to break so I will have to see.



SIDE NOTE

Im going to start with a AL subframe as its a bit safer to work with, its higher so changing it to AL will lower my center of gravity.
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Old 11-30-2011, 03:51 PM   #4
Parx400
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I think we should start with the TT Aluminium swing arm and see what went wrong. It might be something that could be fixed. The TT Germany site has a pretty popular forum but its all in German. Anyone here Speak German and want to ask? I'm sure we could find someone who knows the issues. Hell maybe someone has a cracked on in their garage someone could have as a starting point.
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Old 11-30-2011, 03:58 PM   #5
Jakub
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Both the Factory F650R and the Touratech Race Kit bikes had different swing arms compared to stock.
You can try contacting Touratech for info about there's. The Factory race bike one is unobtanium.

Touratech swing arm.



BMW Factory swing arm (ala Andrea Mayer)

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Old 11-30-2011, 04:05 PM   #6
Damian_74 OP
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Ally Sub Frame

Ally Sub-Frame is on my fabrication list too - please post all
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Old 11-30-2011, 05:02 PM   #7
tmotten
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That wouldn't be to hard. Although you'll need a proper mandrel bender if you want to use the OEM seat because the beams have compound bends in them. The Xc uses OD 20 x 25. Thick 2mm. Not sure on the ali used though but I doubt it's it's super high grade.
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Old 11-30-2011, 05:27 PM   #8
tex_downey
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Quote:
Originally Posted by Damian_74 View Post
Ally Sub-Frame is on my fabrication list too - please post all

Oh I will. three weeks and a 2000+ mile ride home and ill be back to my Garage.

Oh Baby how I have missed you.

the worst part is my GF has the keys and she said I cant get them back for a mounth, but at that rate I think ill just have to ditch the GF, I have work to do.
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Old 11-30-2011, 07:23 PM   #9
LoJack
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Originally Posted by Damian_74 View Post
Ally Sub-Frame is on my fabrication list too - please post all
What have you found for material for the swingarm? The closed I have found that I think might work is 80mm x 40mm x 4mm wall (would be more comfortable with 5mm wall). The alloy is 6060 which I believe isn't quite as strong as 6061, or 6063 (which is close to 6061 and some folks I've talked with consider interchangable). Still, I think it might work. It would be nice if it was a bit narrower, but the next size down at this distributor is 80x30x3wall and I'm just not sure it'll cut it. I wonder how much it would cost to get some custom extrusions?

I think that if I want to do a direct mount shock I'll need more tank clearance, which means I'll need to modify my tank or make a new one. Think it might be better to make a new one. How? Not sure yet, but I'll probably be making an aluminum sub frame as well. 6061/6063 seems the material of choice, as it's everywhere. I considered titanium, but material cost is prohibitive. Still might. It would be pretty sick.

Lojack
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Old 11-30-2011, 07:38 PM   #10
tex_downey
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I considered titanium, but material cost is prohibitive.

+1
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Old 11-30-2011, 07:49 PM   #11
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Yeah, is a 3lb. subframe really worth a $500 materials cost?
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Old 11-30-2011, 08:08 PM   #12
redbastard
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Does it need to be that complicated?

Back in the day I swapped the steel tubular swing arm on my 77 KZ1000 with an aluminum swing arm from a Suzuki GS1000. It used the same diameter swing arm bolt, I just had to shim it with washers. I'm not sudgesting you try to bolt on a swing arm from a 1980 Susuki...or am I ?
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Old 11-30-2011, 08:10 PM   #13
tmotten
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It's not that much here, but still not worth it I thought. It's about A$100/m and you need just over 3m. You need to get it welded as well.
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Old 11-30-2011, 08:14 PM   #14
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Quote:
Originally Posted by LoJack View Post
I think that if I want to do a direct mount shock I'll need more tank clearance, which means I'll need to modify my tank or make a new one. Think it might be better to make a new one. How? Not sure yet, but I'll probably be making an aluminum sub frame as well. 6061/6063 seems the material of choice, as it's everywhere. I considered titanium, but material cost is prohibitive. Still might. It would be pretty sick.

Lojack
This is how. Not only is it only 5 lbs and acts as the sub frame, it also holds 6.7 gallons and allows for 11.5 inches of travel due to the over-swing arm shock position and angle being changed. And, it uses a G650X seat pan that has been finished by Renazco. This seat is half the weight of stock F650



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Old 11-30-2011, 08:16 PM   #15
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Yeah, it's about $30/ft here. Give or take. But then you have the mounting tabs, bits for the exhaust mount(s) and taillight, etc. Cut fee's when you only need 8" of 1x0.25" plate and what not. Think I added it up a while ago and got around $500.

As far as welding goes, I worked at a custom bicycle manufacturer as a welder for 5 years that specializes in ti. Comfy cozy with a torch in my hand and some 3/2.5 on my bench.
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