frame damage effects

I have a 72 LRF with a frame thats had a frontal inpact, the top main tube is bent approx 3/4 , thus shortening the wheel base [i guess] what would this do to the handling? Dont worry i intend to get it put right,or change the frame, There's a frame on Ebay, but again the top tubes bent up . there is a few ebay frames, but i wonder why...crash damage ?

I have a 72 bent frame, its top tube is bent down by 3/8", as the headstock has dropped this has also caused one downtube to bulge outwards to one side and the other has bent outwards next to the sidestand lug. The maintube bend is concentrated just before the support U that comes up from the Z plates so there are no bends in the triangulated areas. One of these days I will take a trip to our local welders and see if I can cut the downtubes so they do not interfere and then apply heat to the maintube bend and straighten it before sorting out the downtubes.

Back in 81 there was a garage on the Pacific Highway , but still in town , with a black S.W.B. Commando on the forecourt .

Investigation revealed " Nah , we got it from the Insurance Company . We just put a chain block on it and pull the front out .
Weve done plenty of the, . They all do that if they hit something . We do them all the time , weve done about a dozen " .

yes . . . well . . .

Some people mightve had a bit of dificulty with the front brake . Adviseable to have a escape route in traffic preplanned .
and get your legs clear of sideswipes . :cry: Thus encourageing a continuous prgression through obstacles .

I suppose the yeilding top tube is a clever Norton design to absorb impacts :lol: sort of crumple zone :?:

Pics please

Just had an Email from the guy selling the bent frame, "He states it's a sold as seen" and as it's still for sale he aint bothered if it will do the job, he as not even revised the listing after being told its bent. is "sold as seen" a total disclaimer?

I would be VERY skeptical of the safety of a damaged and straightened frame being re-used. Once it's suffered a plastic deformation, it loses quite a lot of its strength.

It is a highly stressed structural component and N-V didn't find out until long after it went into production that it was more heavily stressed than the calculations (slide rule back then) had indicated. Unfortunately, I didn't have enough data to set the forces on the fatigue-test of the frame high enough for stronger brakes, and I quit N-V to emigrate before I got the high number of test cycles it would have taken to show a fatigue crack.

With that wimpy 2LS brake, the problem wasn't uncovered in testing. It wasn't until the after-market disk brakes, and Norton's production one, got the braking forces high enough to cause a problem. We'd seen fatigue failures on the AJS Stormer, specifically on the works team bikes. Its frame was very similar to the Commando, but with the top tube attached to the bottom of the head-stock. It cracked across the top half of the tube, just behind the stiffening gusset, rather than across the lower half like the Commando frames failed..

It's a shame that the redesign of the Commando didn't take the same idea as the Stormer instead of putting that ugly auxiliary tube in. On the Stormer, the top tube was split along the horizontal centerline and opened up at the front to be just slightly shorter than the full depth of the Head-stock. At the rear it ended up its original circular cross section. A long triangular filler was then welded into the opening between the top and bottom halves. The stress distribution was actually parabolic, but a parabolic top tube would have been very diffcult to make unless changed to a pressing.

frankdamp said:

With that wimpy 2LS brake, the problem wasn't uncovered in testing. It wasn't until the after-market disk brakes, and Norton's production one, got the braking forces high enough to cause a problem.

Click to expand...

Norton Villiers were certainly aware of the frame breakage problem (and took steps to correct it) only a few months after the Commando went into production, this was well before disc brakes were fitted to Commandos.

It's intresting to know if our Hobit [steve] as broken many frames, if not we can all rest easy. anyone else snapped a frame?

I don't get to chime in here much but I thought it might be interesting to show my frame repair.
Before:
After:

You can also see my new garage door that's going to make the shop MUCH nicer this winter .
I agree that once you bend the frame, you can't regain all the rigidity just by bending it back. But what else can you do. Should be fine for street riding.
Here is the shop that did the work http://www.wascoframe.com/

Wow Roadrash that spine shows twice as much as Trixie or Peel. I see front support but how did you support the other end and apply the rebending force?
Did you check the under tube too for side to side or middle bow?


Amazingly enough so far only broken off the rear loop before I became aware of that issue. Trixie's deer strike hit so hard on headlamp sideways if flipped bike out form under to hit ground and bounce back up then come back down on me with L knee between ground and head which took out knee and later discovered the under tube brace knocked to LH 3/8" and checked against Peels which was still essentially centered. There may be a bit more bow in spine on both Combats but that's so common is a non issue. The cracked framed I've seen here and there were in the mid down tubes a bit above the the gussets. I discovered Ms Peel had buddy breast bulges on front down tubes after all the paint sanded off. I assume crash bar clamp damage someone had welded up but for sure fully tested in drag wheelie landing and gofter hole and wild and wooly ravine play with MX and Trial bikes. I think pre-Peel 7th day drag launch tire fold up WHIP down put so must twist in the swingarm even GT Enterprises could not straighten it. I don't know if my own crashes and clutch dumps bend pre-peel's cradle or not but it was found tweaked as it unswrung on complete tear down and then the crankcases were found twisted .003+ on the dowel pins binding cases horrifically together empty or not. Snapped off foot pegs and bend foot stalks till just removed them for rear sets and found much better posture and control.

Impact wise fork tube bend well before frame on front only impacts.

Next Peel has triple triangulated crash cage but that is for public not really letting hair on on a tract so the extra stiffness may interfere with her flights of fantacy on compliant frame energy storing and release.

Hobot- How's the knee now? Bikes are easier to repair.
I have no detail for you on exactly how Wasco jigged up the bike to bend it back. Richard's shop is full of proprietary rigging he has developed over decades. The top tube wasn't the only thing wrong with the frame once they got into it. Now the frame is back to factory measurements and geometry.

UGH, i had spent last of wad on the Combat on move to Arkansas and no job sight found yet when I was helped off track and everything below knee stayed on ground as I stepped up till skin sprung it back into shattered remains to see jean shift 3" to the side and R foot going sideways to about touch R hip before fully on ground. Crowd was really excited on seeing a Norton open header SnOrton-ing so cheered to high heaven on me getting up just after the x-mass tree then total silence when they saw the damage that took me down. I was stick as stomach I'd ruined my life as no money for new knee and thought it would just heal a solid lump. But I'm deeply trained in this and remembered rats with knees completely drilled out, one bunch ace wrapped another casted and a 3rd in clock like motion device, so did the tolerable motion approach and completely regrew knee better than new in 7 months. That was '99, deer strike frame damage knee was in 2006. Superbike School took out L ankle so foot faced up in '01 and goats got the R knee in 2009. Ultra light save on my feet made them look like dead chicken feet in '83 and took a screw to hold some pieces together. Told never will run well again let alone walk right but i'm 61 now and no joint issues at all by stretching neck taking minerals complexes and avoiding medical route and expenses.