By James Morikawa
I will write about "Checking, and Correcting for Rear Triangle Alignment". OK, so here I go, another webpage creation on "Notes on Framebuilding".
It's usually the case, that after I weld and braze together the rear triangle, it ends up with mis-alignments caused by heat-distortion. Example — The seat-stays or chain-stay upon welding, may now have weld-stresses, which causes them to pull inward.. Another example — one side of the triangle pulls outward. It's mis-aligned if it doesn't remount easily back onto the frame-jig.
The frame-jig could securely hold the welded/brazed triangle in alignment, but remove it from the supporting frame-jig, and weld-stresses may cause it to spring out of alignment — having no securing frame-jig to counter-act those stresses. Anyway, the idea is to pull the triangle back to alignment, so it remounts back onto the frame-jig, easily and smoothly. I also have to consider this, that to make any re-adjustment to the frame-jig from it's orginal settings, to faciliate the remounting of the rear-triangle back onto the frame-jig, is deviating from the frame's design specifations — something I don't want to be doing.
And thus, on the rear-triangle pictured below, I have some alignment checking and re-alignment to do.
I do use a Henry James Alignment System for the task of cold-set aligning. A nice thing about the Henry James is, with minimum floor space , it can be stored-away, and kept out of the way. A very good thing in a small shop like mine.
This my Henry James Alignment System set-up for re-aligning the triangle. I've removed some of the attachments that came with it, so it's not as complete as a newly purchased from Henry James Bicycles.
Notice that I've bound the top section of the seat-stay with nylon rope. This is to prevent the possible separating of the silver-braze-joint at the seat-tube, due to the bending torque that may to be applied.. The system is capable of much torquing force, so alignment is done carefully.
I wish I had the skill to tig-weld this seattube-seatstay joint. I am amazed at those tig-weld builders who can do it well.
I won't go into detail on how this Henry James system works, just too much writing at this time — please forgive me. I would care say, that after using it for some time, I've gained a feel, and judgement in the use of it.
In the above picture, I'm checking for the drop-out spacing, that should be 130mm for this road frame. I usually make it about 2mm wider (132mm) for easier wheel removing and installing — about 2mm wider than a 130 road rear-axle spacing.
Above, I'm checking the seat-tube-center alignment, near the bottom section of the tube.. There should be minimum difference between the tool's straight-edge, and the left and right side of the seat-tube.
Here, I'm checking the chain-stay centering, using a Nortac T-shape tool, purchase from Nova Cycles.
Oh, yes, can't forget this alignment, using my Park Dropout Alignment tool.
I think I posted these pictures before. Anyway, in the above, I'm checking alignment for seat-tube centering at the top-section of the seat-tube. I hope the pictures describes the alignment check. Also, these are pictures were taken after, all needed alignments were done, and the seattube centering is good.
The alignment of this rear-triangle is very good. The wheel-rim's diametric centerline should spin centered to the back-vertical-centerline of the seat-tube. The spacing between the the wheel-rim, and the left, and right seatstays should be of minimum difference — same also for the chainstays. The bottom-bracket is 90 degree square with the seat-tube, and is also parallel to the linear center-line of the rear-axle — it's also 90 degrees square with the wheelbase-line. All that jargo just means I have a well aligned rear-triangle thats, "good to go".
Don't think I haven't had rear-triangles that didn't meet my standards. Those experiences sure did make me cry, and illicit classic four letter words from my month. Those experience were always costly in time and money. Ouch, and double ouch — darn did they hurt.
OK, so once I have the rear-triangle, I can move on to welding up the front triangle.
P.S. I hope you notice my writing getting better? I hope I'm using such writing symbols as, coma, dashes, italics correctly. Oh, well, correct me if you like, it's a writing experience for me.
That's it for this webpage. I'm out of here. Goodbye.