bending the frame rear loop

I was almost finished with mine after six years of work when I saw the rear frame droop which Mr. Hobbitt referrs to. This is my third frame and I was not happy. We were able to get it brought back up using straps, wood, and a little help from the hoist.
When I asked the guy how could this possibly happen? His reply was "fat chicks".

.

Yeh, change one thing, change everthing. You might end up chasing your tail.

By the way, I assume the bike tracks straight when you ride it or you would have said something.

Dave,
I've seen a Commando on a straightening table. You'll be amazed at how little force it takes to bend those long, thin walled, one inch tubes. Believe it or not, you can do it with your bear hands. Or if it were me, two of the biggest people I know and a two foot 2x4 between something vertical and solid and the upper shock mount. One guy holding the headstock, one doing the shoving, and me holding the ruler.

Two options come to mind about dealing with the bent loop:

Old guy option: think about it until something else equally annoying comes along and you forget about the first thing.
Young guy option: jump on your Norton to get a case of beer and notice the pretty woman working in the the cold beer store.

Stephen Hill
Victoria, BC

Can you see where it is bent?

I know you can see the end result, the mis-alignment at the rear but can you see a bend, or bends? at the root of the loop? Are both sides bent?

Or, It might be that one side of the loop was cut shorter than the other before it was welded, or, one side was "tacked with a gap" while the other side was "tacked tight" before the final welds were done.

So, was it mis-cut or mis-welded at birth or was it bent at some later time? and that goes to whether "bending back" versus "cutting and re-welding" are prescribed.

It seems I have replies from it's easy to it's to dangerous. Right now I'm doing nothing. I'm going to mull over the winter and do some investigations.

That said, I can put a carpenters square on the plate at the end of the main tube and clearly see that the angle of the tubes coming off there to the rear loop are at an angle to the right. If it came that way from the factory or happened later, who is to know. The bike tracks fine, so it's not a big issue, just that from straight back looking at the license plate it is not centered on the rear wheel, which is centered on the frame tube and headstock as close as I can measure which is probably not much under 2mm.

Dave
69S

FWIW, the only brit bikes I've owned that were "off" had been Triumphs (fender never lined-up perfectly with the rear tire). I'm surprised at how straight my Norton is comparatively.

Here is how I would do it. Lay the bike carefully on it's right side. Put your knee on the frame just behind the rear shock. with your right hand, pull up on the frame loop. You'll have to pull pretty hard but around 2 or 3 hundred pounds of pull should do it.
So, seriously, I would wrap the frame in masking tape and then build a wooden piece to go into the rear loop. Using deck screws I would sandwich the rounded piece of wood into the rear loop. Then build a similar wooden piece to go right where the rear shocks mount. On this one I would take in both sides with a piece of wood between the shock mounts. Screw a 2 x 4 across the top long enough to also connect two wood blocks on the outsides of the shock mounts. Now, drill a 1/2 inch hole down through that set of wood blocks at about the center of the frame. Then drill the same dia. hole through the wood blocks mounted around the end of the loop. Bolt a 2 x 6 on its side across both sets of wooden blocks sticking out the back of the frame at least 6 feet or so. Now strap the bike to a wall on its right. Pull the 2 x 6 away from the wall until the frame is straightened out!! That should to it.
Cheers.

Whoa whoa whoa... save yourself the time and headache, don't chip or burn your powder coat by attempting to bend or cut or weld. Here is what you do to the frame:

Nothing.

Here is what you do to the FENDER. Sell it on ebay and use that money to put toward a fender that has not been drilled for mounting. You see where I am going with this... Line up your fender, drill and shim if need be.

I walk the path of least resistance 8)

Just checked my frame rear loop..its 1/2 over to the right! are they all the same?

OK, everyone check their frame rear loop and report back.

I did try moving the rear fairing over when I was installing it, but it just didn't seem to want to go, I even tried bending the guard and all I got was a dent in it under the loop. I was blaming it on the guard, but it's the loop and the farther back you go the more it's out.

The Nortons are all so different. I got one of comnoz's breathers, and my frame brace by the sump plug is so close I couldn't install it. He said it's the only one he has had returned. Just my luck.

Dave
69S

DogT said:

The Nortons are all so different. I got one of comnoz's breathers, and my frame brace by the sump plug is so close I couldn't install it. He said it's the only one he has had returned. Just my luck.
Dave
69S

Click to expand...

Cycle World March 1971
"Two modifications differentiate the 1971 Commando frame from the first one. The crossmember underneath the engine has been moved forward slightly to facilitate quick removal of the sump cap..."

As opposed to the slow way which is to pull the engine? At least they got the important things right, it's straight where it counts..

I can get a box end spanner on the sump plug but not a socket. Just enough clearance to get the spanner on it. Jim's breather was just too big. I suppose if I had the gumption, I'd move the brace, but it's a bit late now.

Dave
69S

Been meanig to say , on a ' race hack ' was fairly standard to rn a plug in ( brazed ) rear loop , That'd be the 'next size down ',
so disapearing into the bushes backwards , the lighter ' sacrificial ' rear loop takes the impact without bending the chassis .

AND , yours is ' 3/8 in. ' off centre , reading the ruler , 3/8 per side = 3/4 total , but its only half that ' over ' .
The Big Check should be if the front area is ok , a few bits of wood taped / rubber banded on. Vertical , to BUTT a ruler against will get a few accurate measurements to your centerline datum . A bit of Builders String or Fishing line , tied off
tensioned , is moveable and easy to adjust and SIGHT along. Chalk line of a block of wood & spacer , run along the main tube , even if it gives two parrallel lines , you know the C/L is half way bertween / Splits it .

Engineers supplies have Engineers Chalk ( like a Builders Pencil , rectangular X sedtion ) and Injuneers dip it in oil
for marking old rusty steel , to economise on wear . Wont go on anything smooth then though .

AND you really need a STEEL RULER , with the ' zero ' datum , on the end , so it reads from what its butted against .

Bare Frame , Looping String lines from A to Z gets a spider web , standing clear , if all the lines line up , It would appear to
be Straight . Youre :lol: Laughing .

AS FOR SLEDGEHAMMERS , Olde Perry had me hold a Commando fram down while he assulted it with a Large Rubber Sledgehammer . Talk about bricking , thought Id get the Frame in my teeth .
Trade Secret ; You need a Rubber Sledgehammer . :shock:

Dog T is correct his loop to drawing is out, mayby due to some past fall over?
must admit my rear fender is slightly twisted making it look worse than it is, infact my mate give it a firm pull and held it. looked good, only to spring back again!

AS FOR SLEDGEHAMMERS , Olde Perry had me hold a Commando fram down while he assulted it with a Large Rubber Sledgehammer . Talk about bricking , thought Id get the Frame in my teeth .
Trade Secret ; You need a Rubber Sledgehammer . :shock:[/quote]

really :?:
They definitely used a sledgehammer on the frame I had straighten out at the front end on a Motoliner jig- my ears are still ringing

Had the bike out today for a run and got back, started fretting about that darn rear loop. I already tried bending the tangs on the seat that go under the rosettes, so I figured I can bend the metal without the powder coat flaking off. I bent the dickens out of the seat tangs to get them to line up. So, here's how I proceeded, hobot style.



6 lb. maul, 2x4 blocked from front of frame loop to garage door frame, greasy rag over the place I'm going to whack, and place 2x4 over the rag and give it about 6-8 well placed whacks with the maul. Did it in stages to see if it was working or messing up. First few didn't seem to do much, but as I got to about 8 it seemed to start to move and appeared right. Put the guard back on, and it seems to line up pretty good. I think there is something strange about the guard though, even though it lines up with the frame center tube, there is still a bit of bend. It's visible in real live more than in the picture which looks pretty good.



Anyhow, I thought all youse guys would like this one.

Dog

Not perfect but darn near. I could live with those results. Good job Dog!

pvisseriii said:

Not perfect but darn near. I could live with those results. Good job Dog!

Click to expand...

Mine as a nasty bend in the guard, proberly the way it left the factory..not a problem ...just looks naff from the rear!