Frames accuracy

Been looking at threads about frames and the accuracy of.
Recently measured 3 frames looking for straightness. The procedure was as follows.

1. set the bottom rails and rear ISO long mounting bolt level in 2 planes using a precision engineers level.
2. set a straight edge exactly in the middle of the front and rear mounting lugs .
3. Drop a line with a plumbob from the centre of the steering head column tube.

Now it got interesting. If the engine /gearbox is 1/8th to 3/16th's offset to the left, the plumbob should show this by being to the right of the straight edge.
On all frames this was not so. all frames showed the plumbob to be in line with the straight edge. To me this indicates the axis of the mounting lugs is not parallel with the frame. I confirmed this by making a tool to accuratly measure whether the front lugs are indeed centered with the rear mounting. On all frames the front lugs appeared to be offset 150 /200 thou to the left of the rear lugs. The rear lugs were centered on the main top tube. There fore the centreline of the mounting lugs is not parallel withe the frame centreline

The front lugs widths varied from 5 15/16ths to 5.980.
The rear lugs measured correctly at 8 3/4.

All frames had a bend in the top main spine tube of about 1/16th inch. The bend is exactly where the welds are. Is the concentration of welds where the rear loop and the headstock brace meet causing the top tube to distort and perhaps this was another quality control issue. There is a lot of weld here on relativly thin tube and i do not know if the welding jigs took this into consideration. is there such a thing as a dead straight top tube. Would a bent top tube alter the steering angle, if so is this enough to change handling.

the point of this is to ask if the stories about bad handling commando's, especially where the fitting of a steering damper was necessary , can be traced to particularly bad manufactured frames. perhaps the old Monday or Friday bikes. all comments gladly recieved. I do think now that the frames are not that accurate. There are so many stories about good and bad handling bikes I wonder sometimes if we are talking about the same bikes from the same factory..

Are Commando frames mild steel or Reynolds tubing. Be handy to know if I have to ever make welding repairs.


Thanks to all replies. This is the beauty of this forum, all the knowledge out there being enthusiastically shared freely around the world. Politicians could take a good lesson from this forum, so many contributors and so little squabbling. Altruism at its best.
Thanks again, wish you all the best
Bradley

L

Very interesting Bradley. Could it be that bad handling in Commandos has at least as much to do with wheel alignment as with isolastic adjustment?
I hadn't even thought about wheel alignment before seeing it highlighted on another thread, and I noted that my back wheel is not in a direct line with the frame spine.
My front wheel has always been out of centre within the forks. Something else to work on during this rebuild.
As I noted on a thread about isolastics, my front lugs are more than 2mm closer together than specified in the manual, making it necessary to modify the new isolastic kit to fit.

Cheers
Martin

"200 thou" and "1/16th" of an inch are probably better than the tolerances allowed after the frame cools from being welded in a jig - and then (considerable) use ??

Whatya gunna do with it, race it at over 200 mph ?
At normal road speeds, with all the other bits that can be slightly out of adjustment (and may well cancel each other out )(to an extent) you'd be lucky to tell the difference. ?
If they all tend to the same side though, may be different...

The steel in Commando frames is nothing exotic - but is quite thin, so be careful how you weld it, or heat it - to 'correct' anything.

B.Rad said:

Now it got interesting. If the engine /gearbox is 1/8th to 3/16th's offset to the left, the plumbob should show this by being to the right of the straight edge.
On all frames this was not so. all frames showed the plumbob to be in line with the straight edge. To me this indicates the axis of the mounting lugs is not parallel with the frame. I confirmed this by making a tool to accuratly measure whether the front lugs are indeed centered with the rear mounting. On all frames the front lugs appeared to be offset 150 /200 thou to the left of the rear lugs. The rear lugs were centered on the main top tube. There fore the centreline of the mounting lugs is not parallel withe the frame centreline

Click to expand...

I think I understand what you are saying (some photos would help though) but have you checked with the front Iso mounting and cradle in position as that is where you should measure the true offset.

B.Rad said:

All frames had a bend in the top main spine tube of about 1/16th inch. The bend is exactly where the welds are. Is the concentration of welds where the rear loop and the headstock brace meet causing the top tube to distort and perhaps this was another quality control issue. There is a lot of weld here on relativly thin tube and i do not know if the welding jigs took this into consideration. is there such a thing as a dead straight top tube. Would a bent top tube alter the steering angle, if so is this enough to change handling.

Click to expand...

The bow in the top tube (which has been discussed here a number of times before) is not only very common in later frames but also rather apparent so I can't see that it would not have been taken into consideration during frame production.

B.Rad said:

There are so many stories about good and bad handling bikes I wonder sometimes if we are talking about the same bikes from the same factory..

Click to expand...

Commando frames were of course manufactured at various times by two different companies, Reynolds Tubing and Verlicci in Italy so the same bikes but not necessarily identical frames. The Italian frames were reputed not to handle as well but I don't know exactly how true that was.

B.Rad said:

Are Commando frames mild steel or Reynolds tubing. Be handy to know if I have to ever make welding repairs.

Click to expand...

An ordinary grade of mild steel, certainly not Reynolds 531.

I've read about slightly bent spines for decades and both my Combat have ~1/8" gap at ends of a straight edge. I can guarantee there is no ill effect on handling. If ya can even assemble power unit into frame then it may bind to vibe like crazy but it'll be undetectable in handling. There is some mention by Norton and others to do the front shim/venier adjustment on the LH side which would tend to nullify the factory offset. Also check the under spine tube as I've found one bent to the LH like 3/8". Main frame issue is getting the front tab faces parallel to each other. Frame is rather thin mild steel so while investigating take a screw driver and stick in through a front tab and lever on it to see how the tubes twist a bit, not much but road loads can do this which one can contact for vibes and two can spring back to add to the hinge magnifying phase. R swing arm is splayed to R then end angle back to match L axle plate.

Verne F from CA had to straighten my frame. He said that about 10 or 15% of the Italian frames had misaligned isos. And FYI if you send him a frame, youd better not be in a hurry. He's straightened Cdo frames for Kenny D for years. And still does. Not that this what you're experiencing, just some thoughts from one B.rad to another.

Is that Verne Funeston you a referring to? If so, he has some deep Norton roots, including a connection with C.R. Axtell and Mike Libby, I believe. I know he worked with Nick Deligiannis, the guy who built and tuned the Aldana #13 Norton.

Variety is the spice of life they say.
Here's what's what on many frame and power unit components details by Ken Augustine now on mc-engine list. It don't really matter that much as long as assembles decently.
http://vintagenet.us/phantom/wsc.html

My current ride Trixie is definitely tweaked from severe deer impact the high sided bike many feet in air to land on me to bend both forks and spinal under tube so head steady require offset spacing to the LH side even more than designed in. She's as good smooth handler as any un-tammed factory Commandos. I had to remachine front iso mount tube to fit again even with harsh spreader all thread and 2x8" block sledge hammered between down tubes for any help to recovered the distortion that hit when taken apart, then hard pounding to get iso to slide in fully. I even had to reduce the .001" gap setting and have never gone back to open it up again as no reason too. two nine hour days on Trixie prove she's smooth operator and a few lay over half a tire width skip outs testing stability prove as good as any other un-tamed Cdo. So be as anal as ya like and I like to see that as rest of us, but its mainly academic endeavor is all. BTW I likely have way way more miles on broken axles in city traffic to free way speeds and have lost all respect for anything aligned back there bu the chain sprockets. My attitude under neath is un-tammed Commando are dangerous and suck to high heavens in the handling department good as they can get w/o full linkage help, which also stifles more annoyance sensation you all don't even know your suffering with yet.

What we need is a way to get front iso tab faces parallel to each other as that's where all the planes of power motion and road action stability focus on.

JimC said:

Is that Verne Funeston you a referring to? If so, he has some deep Norton roots, including a connection with C.R. Axtell and Mike Libby, I believe. I know he worked with Nick Deligiannis, the guy who built and tuned the Aldana #13 Norton.

Click to expand...

Same guy. Wasn't aware of his roots, just knew he was only one on the left coast with Cdo straightening experience. I believe he worked at Buchanans for a while before setting off on his own. After they stopped fixing frames he got all of their old engineers drawings for loads of old bikes. If you use him, be prepared to wait a long time!

I didn't know about Buchanans. He and Nick worked together at a Honda(?) shop in Van Nuys back in late sixties, maybe early seventies.

If it is possible to get the frame"spot on" how much would 60 bhp pulling it to one side snatch it out ot alignment?

I have another question, If you were going to do a frame up restoration on an otherwise ok handling bike, would it be worth getting the frame checked and straightened?

Depends upon the trouble/ time/cost ,if its good now..whats the point?

Handling extremes is what fascinates me most on cycles. The first part of genus of Commando chassis is the engine power and thrust don't distort the frame as all the loads from chains are applied through the power unit cradle then into the frame via the self balancing thrust though isolastics The second part of isolastic genus is the taking up of tire vector conflicts, up to a point then can kill ya if rebounds not tamed somehow. I have done the experiments of too much power hits for the design to find the swing arm can get pulled/bent to LH side and the engine cases can twist on their halves to bind-lock up on the case dowels but no effect on frame or mount tabs holding the distorting power unit. Shafts and sprockets also get messed up by too much power hits, but not handling. I have found if frame is tweaked visibly the only other thing detectable is difficulty to assemble and more vibes from binding mounts but UN-detectable handling effects. It takes severe road loads to distort the frame via hi side saves and un-saved crashes, which don't seem to be a factor the rest of ya are experiencing as handling limits. Handling issues show up d/t the springiness of thin steel tubes, factory over sights in forks and the isolastics rubbers rebounding in various ways and of course condition of tires and suspension components like forks and shocks. Its pure fantasy to think minor frame errors have anything to do with handling upsets.

Much as may offend and annoy I have totally solved any and all handling issues in Peel so building power to take more advantage over the mis-led elite sports bikes designs but didn't bother a whit-worth on her frame beyond easy assembly with some whacks here and long levers there. Its life and death severe tested trip to me, no speculation on my claims.


Trixie frame was deer impacted forks destroyed then hi sided landing distorted, plus swing arm tweaked in a hi side out of a ditch log truck forced into, that tore the shock mount out on RH side, to point front iso tube had to be cut down further .060" and all thread spreader and big wood block bashed in to fit engine and then levers and bashing plus 1/4" of assymetric shims to get head steady to fit w/o bind d/t the under tube cocked to L from landing and shattering my L knee but she's as good and smooth and secure handler as any un-tamed Cdo out there, but still a corner cripple if trying much G's in turns.

If ya really must have a spot on frame then send off to GT Enterprises and buy another frame to ride on in mean time then sell off the repaired frame or the extra used spare frame for some recoup while still riding in the interim.

Steve, where the commando frame twin front down tubes regarded as undersize at the design stage? if so then someone must have thought the frame was not strong enough? ...to not handle the power ..weight...or what :?: memery was the tubes should have been 1 inch :?:

Well I am planning to do a full cosmetic Job this winter so the frame will be down to bare metal, no good reason other than it's nice to have everything working as well as you can get it.

spelky said:

I have another question, If you were going to do a frame up restoration on an otherwise ok handling bike, would it be worth getting the frame checked and straightened?

Click to expand...

Does it look like its been in an accident? If so, then yes. Check the frame and the swing arm.

Postby john robert bould » Sun Aug 26, 2012 9:58 am
Steve, where the commando frame twin front down tubes regarded as undersize at the design stage? if so then someone must have thought the frame was not strong enough? ...to not handle the power ..weight...or what :?: memery was the tubes should have been 1 inch :?:

Click to expand...

Dear John in all due respect that's what me and everyone else in the world thought and felt too - until all linked together compliantly like Ms Peel. I don't think you and rest of Nortoneers but likes of TC consider the hi power, I'm talking, watching out for tire spin or wheelie or whip lash leap hooks ups, so essentially only rear being loaded so frame is relieved but to hold pilot and front up w/o any side loads to matter. But beyond simple drag racing loads Ms Peel takes same power hits while leaned and turning over poor surfaces.
The down tubes are plenty strong enough as far as pure engine power=thrust concerned, but not to handle power loads leaned through forks while front still in traction *and* pointed away from direction desired to turn into. Peel isolates all the various vectors and resonances ALL OF THEM. So much so she is a different animal than any other bike ever fielded, so of course its impossible to relate to or describe to anyone else. Keep working on incremental improvements but Peel flys to new higher energy orbitals, so have left the ordinary behind to discus their dangers with disgust.

As for my own un-tamed Trixie Combat and all the rest like her, my message is all that's needed is just get things close enough it all assembles with least brute force then enjoy the tedium to make it eye candy, realizing none can expect to get a completely disappearing act like Ms 'Goldie Locks' Peel out of too loose or too rigid creations.