Frame crack

  • Thread starter Thread starter Davo
  • Start date Start date
sfcpiet said:
The frames will crack in bog-standard form
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I can vouch for that. I just had mine repaired.

Looking forward to riding again. The bloke who repaired it took forever, but whenever I told anyone the name of the bloke who was repairing it, said the bloke is a legend, and if he couldn't fix it no one could.

Dave Hall is his name. He works four days a week at his proper job, and does motorbike work on the side.

vKGToJx.jpg
 
I have followed the various posts  in the last couple of months on adding gussets to the frame at the steering head. Also did a search and have the factory drawings with the recommended modification. I have an RGS Corsa and no cracks in the frame at present, about 50k km (30k miles). Bike is stripped to bare frame as part of a restoration I am starting. I use it for "normal" street riding and it is pretty stock, stock forks, brakes and wheels. Everyone adds gussets in 2 areas. First extend the current factory gussets down along the steering head to the  horizontal frame tubes.  Second, add new gussets from the bottom of the steering head to the down tubes.  Question...is this generally deemed enough as a preventive measure for normal use?

The factory mod, and some posts, shows adding a cross piece between the two vertical frame tubes below the oil cooler and above the headers. As well it shows a small gusset from the bottom of the horizontal frame tubes (near the steering head) to the rear side of the vertical tubes.  Were these generally considered as overkill for normal use where there are no existing cracks, so most do not bother with these mods, or so obvious they are needed that most don't post pictures of these mods? I am sure there are varying opinions and I welcome the education. Thanks. 
 
When reinforcing the 1000SFC frame, the factory added quite small and thin gussets above and below the "horizontal" tubes only, where they meet the front downtubes.  Obviously, the factory had become aware of RGS frames cracking and introduced these measures to prevent any future failures.  Only found on the last 50 or so 1000SFCs.  Seems they are quite ample, as I have yet to see such a frame showing the "normal" cracks.

I'm guessing the factory opted for an overkill repair solution to take weakened, cracked tubes into account.  Imho, too much gusseting may well show up weaknesses elsewhwere...

piet
 
Thanks Piet.... from my admittingly basic understanding of motorcycle frame design, the frame does need to flex a bit to work as designed. I will make up the  gussets and then off to a "proper" welder and motorcycle fabricator  I know.

i  can chicken shit weld with my small MIG but  this  job is not the place for the amatuer hour.
 
Some photos from the frame guy today. Crack repaired, headstock gussets welded on, frame straightened. He tells me both front and rear ends were out of alignment so someone between me selling it and getting it back has been down the road. Did always wonder why the right hand engine mount bolts were a really tight fit and misaligned compared to the left.




Now Ship Shape
 
chrisk said:
:o The twist in that swingarm is huge.
At least he is doing it properly ............. it'll be better than new.
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Speaks volumes about the design. Bike rode like the frame was straight, never had a single wobble or head shake. Before I had the wheels straightened the rear wheel had a huge buckle, never felt that while riding either and only found out about it from the folk following.
 
Holy shit, that swing arm was very twisted. I'd have thought it would have been obvious looking at the bike from the arse end that the wheel was canted over. Must have been crash damaged to knock it that far out of whack. Good thing you had that frame crack or you may never have got it fixed!  It will be interesting to know whether you notice any difference in handling with everything aligned properly.

 
Dellortoman said:
Holy shit, that swing arm was very twisted. I'd have thought it would have been obvious looking at the bike from the arse end that the wheel was canted over. Must have been crash damaged to knock it that far out of whack. Good thing you had that frame crack or you may never have got it fixed!  It will be interesting to know whether you notice any difference in handling with everything aligned properly.
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On my 81 the swing arm was out about 4 degrees or so the same way... ...............only noticed when changing out the shocks but yes the wheel always did look a bit cantered to the left at the top.

Nothing a couple of hours and a hydraulic porta-power couldn't sort out though. 
 
Don't like the welds at the bearing houses.
Were they round after welding or oval?
Have you milled it after welding together with the upper housing in line with the swinging arm axis?
Or did you do it like the Teufels from Orange country cycles?
Yust a remark
Andre
 
I welded similar bracing into my RGS frame headstock. I was concerned about the welds distorting the lower bearing housing, so I measured the diameter (with a digital Vernier caliper) in several directions before and after welding. There was no measurable distortion within the accuracy of the caliper (0.001 mm). The bearing still fitted OK and it rotates smoothly.

That bearing housing is quite a thick lump of steel and TIG welds don't put a lot of heat into the metal.
 
Dellortoman said:
so I measured the diameter (with a digital Vernier caliper) in several directions before and after welding. There was no measurable distortion within the accuracy of the caliper (0.001 mm). The bearing still fitted OK and it rotates smoothly.
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man, that is impressive, you can measure 1 micron with a set of digital vernier calipers
I can only measure to within 2 micron with my $5,000 Bower Fowler 3 leg digital bore gauges, looks like I got ripped off
FFS
 
andre g said:
Don't like the welds at the bearing houses.
Were they round after welding or oval?
Have you milled it after welding together with the upper housing in line with the swinging arm axis?
Or did you do it like the Teufels from Orange country cycles?
Yust a remark
Andre
Click to expand...

As frame repairs and straightening is all he does for a living I would assume (always risky I know) that he knows what he is doing and has done it correctly. (to within 1/2 a micron as measured with his plastic vernier - for Cam's benefit  :LOL: )
 
his jig is nearly identical to the one Dave Kellet uses here in Brisbane so I believe there is no issue
Dave being the frame guru here and has done a couple of dozen Laverda frames for us so far

 
I wonder if its a Motolinner or home made, there used to be lots in Sydney bike shops before Alloy beam frames became the norm. I had an XT 500 frame moded to reduce the trail from 130mm to 90mm after grafting long travel suspension onto it using a Motolinner. They were a great gadget.
 
Had a phone chat with the frame guy today. Says the frame is now spot on. The steering head was apparently as twisted as the swingarm and the swingarm was also twisted off centre not just off horizontal. He tells me that when he ground the crack out with an angle grinder he noticed that the frame metal was porous at the point where the weld on the gusset had stopped and that there were a couple of pinholes full thickness.

Of more interest was that when putting the rear wheel back on he noted that the bearings were really tight and the wheel did not spin particularly freely. So he checked the front wheel as well. A couple of the bearings in the cush were really tight as was one of the front wheel bearings. One of the front wheel bearings just dropped out it was that loose and one of the rear wheel bearings close to the same. Going to sort it all for me.

The damn crack could well have been a good thing.
 
"He tells me that when he ground the crack out with an angle grinder he noticed that the frame metal was porous at the point where the weld on the gusset had stopped and that there were a couple of pinholes full thickness."

I rest my case yer 'onour

I would lay money that frame welder had part welded the gusset on, and then ground it of realising his placement mistake, and welded on another, not the worst that I have seen, but when Norton where having the Commando frames made in Italy, they were delivered to Reynolds for checking here in the UK before onward despatch to Norton's, Ken Sprayson has stated that they made more profit by checking, straightening or rejecting, as required, than they would have by making them in the first place, how many Commando riders know that they are riding around on an Italian chassis?, the rejection rate was staggeringly high and the cost of each unit, at the time, to Norton,was ?27.00, I wonder how many got sent back or scrapped and how much Reynolds charged Norton for the service, as they had originally tendered to build them and lost the order on price only. British head in the sand, bean counting wankers yet again?

you can see the rust marks in pinholes on the weld and the poor finishing point. Don't jerk the rod off, stir and float off, just like a departing Saturn five.
CLEM
 
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