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Attempt at aluminum subframe

Old 09-12-2010, 04:49 PM
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Attempt at aluminum subframe

The idea of getting an aluminum subframe for my VTR has been eating away at me for some time now (especially given all the weight savings I have already managed to realize). Due to its location high up and away from the c of g (especially towards the rear), I would suspect dropping weight here would have the most discernible effect on handling. While the strength of Al is not up there with steel (a concern for carrying a passenger), virtually all modern sportbikes use it for subframe fabrication (with Yamaha even using magnesium on the latest R6) so it is clearly up to the task.

With all this in mind, I just pulled the trigger on a subframe from a 98 CBR900RR (comes with passenger pegs). My goal is to alter/mod it such as to retain use of the existing (Sargent) seat and bodywork. I am not a welder and don't have a Mig or Tig machine so I'll obviously have to get someone else to do that end of the job but I'll try to do the cutting and fabbing myself. Hope it works out, if not I'm not out too much $$$$$.

P.S. A wet weight of 400 lb would be a wonderful thing

Here it is:
Attached Thumbnails Attempt at aluminum subframe-cbr-sub-pegs.jpg  

Last edited by mikstr; 09-12-2010 at 04:53 PM.
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Old 09-12-2010, 05:03 PM
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You should probably keep in mind that most alu subframes in modern bikes are a bit more sturdy than the steel ones they replace both literally and generation wise...

I made mine not as a straight copy, but added a fair bit of bracing and plates... It's still a whole lot lighter than the stock... And I'd actually guess somewhat stronger too, but that's just guesswork... If I hadn't managed to forget to take pictures of it, I'd show you... But basically a copy of the stock with smaller cross bracings...
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Old 09-12-2010, 05:11 PM
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I do plan to add a lot of bracing as I do carry a passenger from time to time. While I don't have a number as to the weight of the stock unit (still mounted on the bike....), I would imagine there are a few pounds to shed with this mod.

Hopefully it will work out (would sure be a lot easier if I was a welder)....
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Old 09-12-2010, 05:37 PM
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Well... I'm somewhere between novice and complete clutz with a TIG, but I make do... All according to my brother that does it for a living... That never stopped me from being to stubborn to have him do it for me though...

His assesment of my latest work was that it would be merciful to shoot me... Dunno exactly if that was opposed to shooting him, or not... But I did figure out he didn't think it was pretty... He did however say that nothing I ever welded is likely to break in a weld though...

Get a TIG and start practicing... It's useful in so many ways...

Last edited by Tweety; 09-12-2010 at 05:41 PM.
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Old 09-12-2010, 08:13 PM
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Any one have a weight difference on this? I really am curious to see how much weight would be saved.
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Old 09-13-2010, 03:42 AM
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Ballpark figures from me working with it, not piutting it on a scale (weighted the whole bike, was more interested in that)...

Before I started bracing it, when it was just a straight up copy of the original, mine was somewhere between 1/3 and 1/2 of the original...

Ended up somewhere around half the weight I'd say... And then I was bracing the hell out of it, I don't want it to fail since I frequently carry a passenger...
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Old 09-13-2010, 04:08 AM
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Originally Posted by Tweety View Post

Get a TIG and start practicing...

I agree, everyone should have a TIG machine!


Rex

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Old 09-13-2010, 04:21 AM
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Originally Posted by bjorn toulouse View Post
I agree, everyone should have a TIG machine!


Rex

Nice toy! I have no concept of that brand... Around here everybody uses ESAB's for some reason (Ooooold Swedish brand)...
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Old 09-13-2010, 04:28 AM
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thats a lincoln, thats some top of the line goodness right there. id love to get a tig i just dont like the cost of them so i use my mig for what i can
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Old 09-13-2010, 04:45 AM
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I'm using an ESAB TA34... That's basically top of the line... It was molested by the previous owner, and ESAB denied his warranty claim when he fubared it himself... I repaired it, so now it's working nicely again...
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Old 09-13-2010, 06:08 AM
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Perhaps we could get inderocker to weigh a stock one to get an idea....
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Old 09-13-2010, 06:54 AM
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I have one hanging in my garage. I'll go weigh it. I too would love an aluminum one. Same with the Fairing Stay. Can't wait to hear about the cbr modded one. If it's easy, ebay will be busy.
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Old 09-13-2010, 07:09 AM
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Great, thanks! I have a Graves aluminum fairing stay waiting to be installed (1.7 lb weight saving BTW) but I have to mod it to accpet the RC51 speedo I bought first. That will get done this winter when the bike is hibernating (same goes for the sub-frame)
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Old 09-13-2010, 07:56 AM
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Stock sub frame. 6.78#
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Old 09-13-2010, 09:17 AM
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Originally Posted by Tweety View Post
Nice toy! I have no concept of that brand... Around here everybody uses ESAB's for some reason (Ooooold Swedish brand)...
In the USA the two big brands are Lincoln and Miller..

There are other brands, but those usually are either: owned by one of those two, cheap Chinese junk, or specialty equipment.
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Old 09-13-2010, 09:43 AM
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Originally Posted by lazn View Post
In the USA the two big brands are Lincoln and Miller..

There are other brands, but those usually are either: owned by one of those two, cheap Chinese junk, or specialty equipment.
Let's just say if you ever used a stick welder... Well then you have used tech developed by ESAB... The guy that founded it invented the use of coated electrode sticks... Around 1904-1906 I think...

Other than that it's kind of the same as around you, either Chinese crap or copies of ESAB's stuff... Or special...
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Old 09-13-2010, 10:24 AM
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what is the weight difference?
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Old 09-13-2010, 10:26 AM
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I'd say mine is about half the stock... possibly a bit less... so around 3-4 #
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