Frame Width at Front Engine Mount

[Swarfcut]

 That got me running back to the shed with a set of plates and a crankcase!

   Plates on the cases measure 3" to their outside faces, which as expected matches the dimension at the front edge, thanks to the spacer tubes. A perfect fit for a perfect frame.

  My frame has a  wider gap than the 3" shown in the above diagram. In plain terms a good half inch is missing so on the face of it, my frame also differs from the published spec. But a closer look and feel indicates the top lugs have been ground back, and from the front view are level with the downtubes, if that makes sense. An undamaged and unmolested frame would have those lugs extending further in to the centreline of the frame. With is a good half inch in total missing, good job I found it now.

  Apologies for confusing, but until a moment ago I thought my frame was kosher. It isn't, and as the bumper stickers used to say "Sh*t Happens"


Cheers.

 Swarfy.

[MrShifta]

my 1954 Golden Flash frame which was unmolested and unitl I stripped it a few weeks ago had never been apart from new is on the bench so I have just checked it  and the top lugs are 3 1/16"  apart and the lower pair are 4 1/16" apart. Give or take a few thou.  While we are on the front mountings subject I dont have any, are there any differences between years ?  can I just buy any pair off fleabay.

Richard I am so sorry to see you have a problem, being at the same stage I would be devastated mate.

[RichardL]

Hey guys,

Delivered my frame to the welder this morning. I think there's more story to tell here, but I have a question that I don't want lost in a long post. When I told the welder I was surprised by the brittlenes of the tube, he asked if I knew what material it was, as that would help him choose the right welding rod. So, anyone know the metalurgy of our frame tubing? Also, the wall thickness (though he said he would learn that when prepping the weld)? Could use this info before Monday morning.

I was way too scared to take RD's recommendation to spread the frame +1/16" at the mount because there's still another crossmember that could be broken. Instead I took it out about 0 030". If it springs back under 3" I'll just spread it a little when mounting the engine.

I've attached a few pics - the crack before and after spreading, and the spreading setup. I want to talk about a couple of them, but too tired right now.

Richard L.

[Greybeard]

Richard, although I tapped 'Like' I'm sorry that you are having this trouble.

[RDfella]

"I was way too scared to take RD's recommendation to spread the frame +1/16" at the mount because there's still another crossmember that could be broken. Instead I took it out about 0 030". If it springs back under 3" I'll just spread it a little when mounting the engine. "

I appreciate the crossmember behind would come under tension, so I'd have drilled a 1" hole in a wood block, cut it in half through the hole, then used the halves outside of the frame next to the currently cracked tube to allow a strong clamp to prevent spreading there without tube damage.
If, after welding, the frame is still too tight up front, I'd be inclined to ease the mounting lugs rather than have a frame under constant tension. That, plus engine vibration, could start another stress crack.
As for welding rods, the A series frame steel is almost wrought iron - no fancy alloy here, so universal mild steel rod will do. Always worked for me. Tube thickness? Around 3/32".
How are you getting around re-finishing the frame, seeing it was powder coated (if I recall correctly).
Wishing you best of luck.

[Swarfcut]

  To add to RD's thoughts, and maybe a bit late now, but before welding, a frame needs to be in the least stressed state as possible, clamping where required to align mountings in their correct location and applying heat to the frame tubes as necessary to relieve any tendency to spring back. For the actual repair the best result will be a deep V out of the crack to allow weld penetration through the entire wall thickness of the tube. It's easy just to lay a bead of weld over the crack, but this will not have anything like the strength of a proper V cut prepared weld.

 The S/A frame construction is welded rather than brazed, so heat should not be a problem. Being "portable" all round access will be easy.

 Swarfy.

[RichardL]

RD,

I was about 1/3 of the way to being on your wavelength. I considered clamping to avoid stress on the second crossmember in order to put any deformation across the longer span, but my thinking was to clamp at the second member. Didn't think my bar clamp was sustantial enough with its squeeze activation and rubber jaws. In retrospect, I think it's a good thing I didn't follow through with that. So, having gotten to 0.030", I figured it was worth a try.

As for being under tension when stretched for engine fitting, I would think the issue is the same if 0.030" becomes excess width that is clamped.

As for relieving the lugs, I've done that a bit already by removing excess powder coat. There's another story there, too long to add to this long post.

As for refinishing the frame, I'm going to use bondo to make up the powder-coat thickness, then, rattle-can gloss black. Though I want it to look good,  I'm not trying to build a concouse competition show bike to be judged by experts. No normal person will see the repair.

Finally, thanks very much for your thoughts on the metallurgy.

Adding a pic of the frame swaddled to avoid scratches and spatter, though the welder tells me spatter is not an issue with TIG welding.

Richard L.

[RichardL]

Swarfy,

Thanks for your thoughts. Yeah, way too late for adding heat to relieve stress in frame tubes, barring hundreds of dollars in powder coat and a month delay. Also, I'm guessing the criticality of stress due to 0.030" of spreading is not enough to warrant such good practice at this piont.

The welder is an expert who has been certifed for over thirty years. I wouldn't think of telling him the basic techniques of the trade. With regard to the metallurgy, I figured getting a little special knowlege from the forum might add to the mix if, indeed, there was anything special about it.

There should be pics of the weld before the end of the week.

Richard L.

[RDfella]

If it helps, I needed to add an extra mount for my project's engine. Shaped a tube and made it tight enough it had to be driven into place. Arc (stick) welded it using 2.5mm Euctectrode CP1436 (apparently now replaced by 35276) @ approx 90A.

[RichardL]

Pictures of the weld as well as the collateral damge done by backside of welder's grinder. Not sure why he thought this was OK versus finding a smaller diameter grinding wheel. Anyway, I'm very happy with the weld and that I've found instructions on repairing powder coat.

Now, to the more unfortunate bit. The frame sprung back to almost where it started. In my head, designing a fixture to hold my disk grinder level with the surface of the mount tube when grinding about 0.020" off each tube.

Richard L.

[muskrat]

G'day Richard.
To slim the the mounts down get one of those kitchen tap reseating cutters and mount on your drill using a through bolt through the mount to keep square. Bit hard to explain with a keyboard.
Cheers

[RichardL]

Musky,

I hadn't thought of that tool, but know exactly what you mean. If it fits between the mounts and there's a way to drive it, I wonder if it will work on steel vs. brass.

Richard L.

[muskrat]

G'day Richard.
The cutters screw onto an 8mm bolt (left one in pic). Put bolt through left side mount lug, screw on cutter to do inside right mount lug and visa versa.
 I have used them to spot face steel and aluminum, and even reduce the height of valve guides for big cams!
Cheers

[RichardL]

Musky,

Saw your post just after setting up the rig in the photos. Literally told myself that now that it's set up I should stop and think before going ahead so that I could hear any "STOP!"s or "Go for it!"s from the group. Your reseater seams common in Oz, and, maybe, Amazon, but the three local hardware stores I checked had an inferior version for max 1/2" seats.

Richard L.

[RichardL]

Whoever was about to say it, that's what I was thinking. I need a lock nut against the grinder.