Back Bone Brace tube

Lester

Lester

XS650 Junkie
Messages
528
Reaction score
1
Points
16
Location
Norway
Hey Guys,

Any thought or know how about altering the angle of the back bone brace tube.
I would just like to stuff it alittle further up there so the tank I plan to use will cover it... just a looks thing but I don't want to weaken the frame too much.

See my sktetch... picture stolen from this site.... from Travis I think.

Back Bone brace tube.jpg


Thanks
Lester
 
I've build bike without that tube at all, you can change the location of it easily enough and the bike should remain plenty rigid
 
Punkskalar said:
I've build bike without that tube at all, you can change the location of it easily enough and the bike should remain plenty rigid
Click to expand...

Hugh, would you say taking out that gusset, isn't that big of a deal then?
I know there's been much debate over it, but, you've built/seen quite a few 650's.. So, with that being said... Have you seen any problems with builds that have no gusseting, back bone, or a combination of both?..
 
There are people who believe "the factory did it best" and will argue tooth and nail that nothing should ever be changed. That said, I see much heavier bikes built with much less bracing in the headtube, and they do fine.

For a full on race machine, stiffening up the frame is a must of course, but for 99% of us, these frames were full overbuilt to start with..

Hugh
 
Thanks for the input guys, interresting.
I'll keep you updated when I decide how to go about it.
I'll probably just change the angle.
Who knows, in its day it may just have been put there to hold the coils neatly.

Any more suggestions are welcome

Lester
 
I do not see any problem moving the brace. I do think the top motor mount should be a keeper. I know people have run without the brace. I have seen the rear case crack crack because off this. Just one so it could have a casting flaw for all I know. A lot of bikes are over designed. Mostly because of Liability and lawyers trying to make a buck.
 
Thanks Scabber... I wouldn't remove the top motor mount.... too much vib in these little bike for that. Its just that tube not getting hidden by the new tank is all. A silly looks thing that will be alot of work to sort out....LOL

Remember... too much bracing is not good either
 
I have done around 10 with that tube gone and it gives the bike a longer look with out doing anything. I have also changed out many of the backbones on bikes to use longer tanks.
No Problem
 

Attachments

  • drop_seat.jpg
    drop_seat.jpg
    87.9 KB · Views: 168
  • $(KGrHqYOKnME4N+Kr!EHBOGJkEkS-g~~_3.jpg
    $(KGrHqYOKnME4N+Kr!EHBOGJkEkS-g~~_3.jpg
    116.7 KB · Views: 184
  • 100_0143.jpg
    100_0143.jpg
    253.1 KB · Views: 206
Paulrxs650 said:
Hi,

This is what I did with Peanut Wassell tank from Lowbrow - got rid of the long tube and gussets and welded in some sweeping braces:
100_2663.jpg

100_2664.jpg
Click to expand...

Looks nice man... I think its wrong to call them sweeping braces thou... not braceing much at all... lol look good 100%.:thumbsup:

Could you point me in the direction for some info on that coil... one lump is easier to hide than two. :doh:
 
I was going to ask about the braces you put in there, as they don't appear to be able to brace much to be frank. Better than nothing perhaps, but unless they're tied together, they're just two pivot points for the engine to swing in.

I'm building out a Voodoo Vintage MK4 frame and at the moment have no plans for a top engine brace. We'll see what happens :) Depending on what tank I end up using, I might subsequently build a brace in there - I've seen some guys do some pretty nice looking braces with round bar, but again, not sure how much engineering has gone into them.
 
Paulrxs650 said:
Hi Lester,

That was the best description I could think of :)

The coil is a "Gill" coil from the Boyer Bransden stable of ignition units, nice and compact too!
Click to expand...
Paul, sorry not ment as critisism.... just the conservativ engineer side of me getting to the key board.... my knees start to go on me as I think about removing braces and so on.... lol. BUT I think I'll just neatly remove it... easiest way to go really. I just have to do it neatly so nobody will miss it. I have to get the bike through technichal inspection after fram modification in the back. I'll have a closer look at the brace this weekend

thanks
lester
 
Hi Lester, no apology necessary at all! The same thought crossed my mind :)

Tim, the top, engine mounts, combined with the lower ones combine so that the engine has some bracing at the top and they can't pivot. They were mainly dictated by the dimensions of the tank.
 
Don't get me wrong - not suggesting the engine could actually pivot once mounted. Just saying that the stock top engine mount locks together and can't move once installed, transferring the wonderful engine vibes into the frame vs. letting the top end resonate as much.

In your case I don't know how much the bracing will actually help given it's not locked together and the front braces are pretty long. I'd think the bracing won't do much to keep the engine vibrations minimized / transferred into the chassis.

I'm no engineer of course - so my opinion is worth the weight of the electrons used to transmit it, and some bracing is no doubt better than none.
 
Yeah, pretty much my train of thought - something's better than nothing on the engine mount. I wasn't comfortable having nothing and, like you say, I'm a fan of feeling the engine through the frame! None of these modern rubber suspended engines! :)
 

Similar threads

T
Fork Brace Application and Potential Install Modification Question?
Replies
5
Views
176
The Standard
T
toglhot
Yamaha frame building.
Replies
2
Views
297
Max Midnight
Max Midnight
denverdean1
Is this frame salvageable?
Replies
6
Views
519
gggGary
gggGary
DB90
1981 Chopper Build
Replies
2
Views
399
DB90
DB90
Signal
XS 850 Re Model
2
Replies
27
Views
2K
Signal
Signal
Back
Top