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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Tank mounting misalignment
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<blockquote data-quote="Oldhaven" data-source="post: 54855" data-attributes="member: 2879"><p><strong>NOBODY expects the Spanish Inquisition!</strong></p><p></p><p>Well, I have come to a (mostly) satisfactory conclusion to the bent UFM. the stone axe engineering seems to have helped. (picture 372 is a picture of the setup.) I had the high lift with a 4 foot extension on the handle and a piece of A2 steel machined to fit the steering column and bearing pockets. I gave it all I felt comfortable with, (considerable, I can't believe how strong this thing is) and left it overnight. I know at that point I could feel it at the deformation under load point. That was where I stopped.</p><p></p><p>Next day I t did a post torture set up of the complete UFM</p><p>using the head brackets flat on the mill and the fitted mandrel through the</p><p>headstock. (That 1 1/2 inch A2 did not bend a bit) Using a dial indicator I checked the angularity of the</p><p>steering axis. I found that it leaned to the right about .060" in 4".</p><p>This would mean, If I am thinking correctly, that I would be approximately</p><p>3/8" to the right of the correct position at the tire patch about two feet</p><p>from there. Not too bad, but not perfect. This is picture 373.</p><p></p><p>I then removed the headstock and put it on its right hand side as David D</p><p>suggested earlier. (and I really want to thank him and all who chimed in with suggestions and encouragement). With all the tank mount machined surfaces on spacers I</p><p>found that the steering axis was off to the left by .004 in 4 inches.</p><p>This means that my bending had some effect and I even over corrected a</p><p>bit, but using the same math, I would be off only .024 at 2 feet if the</p><p>steering axis and tank mount surfaces were all I had to worry about. This</p><p>is picture 376</p><p></p><p>So where is the bend to the right coming from? I assume some of it is in</p><p>the tank itself, which is stronger and harder to correct than it looks, and there is a slight</p><p>wrinkle in the sheet metal on the right side, indicating a permanent</p><p>deformation that would be hard to fix. I think I got a lot of that</p><p>with the high lift, but not all. The next thing I looked at was the head</p><p>fork. There is some bend there after all. Relative to the tank mount</p><p>surfaces, both the 1/2 holes in the fork for the head bracket and the two</p><p>tank mount holes next to it show difference of about .095 in 6 inches.</p><p>This means that the tubular part that connects them to the steering column</p><p>is still bent, or rather that the fork is rotated relative to the steering</p><p>column. Since the head bracket is a big piece of metal connected to a</p><p>stiff engine, the effect is to put the steering axis to the right. The real lesson I learned is that the UFM must be considered as a unit, and correcting just one part will not t fix everything and may even make things worse. This is picture 377</p><p></p><p>It then occurred to me that rather than trying to correct the steering</p><p>column rotation, it would be easier to correct the fork. I put a 1/2 rod</p><p>in the top fork hole and placed it not through the bottom hole but just</p><p>under 1/16th inch in a direction to correct the rotation and presto, there</p><p>was no misalignment.</p><p></p><p>So, I think I will try a couple of things in increasing order of</p><p>difficulty, and if I am lucky, one will work satisfactorily. </p><p></p><p>For the fork rotation, I will just put it together and ride it, and see if</p><p>it causes handling problems. If it does, the next easiest thing is to put</p><p>thins shims on top of the head nuts on the left of the front head below the</p><p>head bracket. this will rotate the steering axis to the left slightly.</p><p>Even Phil Irving thought about this:</p><p></p><p>from MPH 378 "Excessive tightening and/or overheating is likely to cause</p><p>permanent deformation of the bolt bosses, and subsequently going round the</p><p>bolts and again over-tightening them eventually results in causing one or</p><p>more of the bolt bosses to co llapse. The one most likely to be affected</p><p>is at the near side of the front cylinder which apparently runs hottest,</p><p>but any of the others might suffer in a particularly bad example. Besides</p><p>being squeezed down below its original height, the boss may have cracked</p><p>away from the top fin, but the head may still be usable. This sort of</p><p>defect, though rare, is sometimes found on engines fitted to hill-climb</p><p>cars without the head brackets in place. It may well be that the absence</p><p>of these components allows the bolts and bosses to deflect outwards, thus</p><p>causing the cracking of the top fin. If such an engine is being put back</p><p>into a standard machine, it is essential for the tops of all the head nuts</p><p>to be parallel to the joint face which will necessitate packing up the low</p><p>nuts wit h thick washers or shims. <strong>This precaution may seem a little</strong></p><p><strong>finicky, but any slight inclination of the head bracket will throw the</strong></p><p><strong>steering column out of line by an equivalent amount"</strong> (My emphasis here). </p><p></p><p>Finally, if that is not satisfactory, I can fill and re-machine one of the</p><p>1/2 holes in the fork to move it that little bit necessary to correct the</p><p>steering axis. this would be a fix that would be useable for another</p><p>machine if the UFM ends up with its correct engine someday. I will not</p><p>worry about the two lower oil tank mount holes since these fit the tank as</p><p>they are and moving them would cause problems. </p><p></p><p>As a bonus, when I reassembled the headstock to the tank, the petrol tank now fits easily, even though I did not completely correct the rotation of the bosses. They improved enough that it is not a real problem, especially if they are done first, before the rear tank bolts. the outer race of the bottom taper bearing also fits better than it did before the torture, and is centered in the pocket with the correct interference fit fore and aft. Though some stretch exists at the sides, it is within the gap filling powers of the Loctite supplied with the Patzke kit.</p><p></p><p>Finally , I attached picture 380, since it shows an interesting thing</p><p>about the oil tank holes in the headstock of this late 1948 B[ATTACH=full]2919[/ATTACH] [ATTACH=full]2920[/ATTACH] [ATTACH=full]2921[/ATTACH] [ATTACH=full]2922[/ATTACH] [ATTACH=full]2923[/ATTACH] . The front 3 seem to have been drilled off the</p><p>cast bosses centers quite a bit, which would rotate the oil tank up at the</p><p>front a little bit. This might affect the angularity of the rear head</p><p>mount bracket slightly, though I suppose this was all done in a fixture.</p><p>I can't see any real problems, as I am not sure it would affect the trail,</p><p> but interesting.</p><p></p><p>So, all in all, a very informative exercise for me, and I can get back to other things awaiting attention, like the RFM and brakes.</p><p></p><p>Ron</p></blockquote><p></p>
[QUOTE="Oldhaven, post: 54855, member: 2879"] [B]NOBODY expects the Spanish Inquisition![/B] Well, I have come to a (mostly) satisfactory conclusion to the bent UFM. the stone axe engineering seems to have helped. (picture 372 is a picture of the setup.) I had the high lift with a 4 foot extension on the handle and a piece of A2 steel machined to fit the steering column and bearing pockets. I gave it all I felt comfortable with, (considerable, I can't believe how strong this thing is) and left it overnight. I know at that point I could feel it at the deformation under load point. That was where I stopped. Next day I t did a post torture set up of the complete UFM using the head brackets flat on the mill and the fitted mandrel through the headstock. (That 1 1/2 inch A2 did not bend a bit) Using a dial indicator I checked the angularity of the steering axis. I found that it leaned to the right about .060" in 4". This would mean, If I am thinking correctly, that I would be approximately 3/8" to the right of the correct position at the tire patch about two feet from there. Not too bad, but not perfect. This is picture 373. I then removed the headstock and put it on its right hand side as David D suggested earlier. (and I really want to thank him and all who chimed in with suggestions and encouragement). With all the tank mount machined surfaces on spacers I found that the steering axis was off to the left by .004 in 4 inches. This means that my bending had some effect and I even over corrected a bit, but using the same math, I would be off only .024 at 2 feet if the steering axis and tank mount surfaces were all I had to worry about. This is picture 376 So where is the bend to the right coming from? I assume some of it is in the tank itself, which is stronger and harder to correct than it looks, and there is a slight wrinkle in the sheet metal on the right side, indicating a permanent deformation that would be hard to fix. I think I got a lot of that with the high lift, but not all. The next thing I looked at was the head fork. There is some bend there after all. Relative to the tank mount surfaces, both the 1/2 holes in the fork for the head bracket and the two tank mount holes next to it show difference of about .095 in 6 inches. This means that the tubular part that connects them to the steering column is still bent, or rather that the fork is rotated relative to the steering column. Since the head bracket is a big piece of metal connected to a stiff engine, the effect is to put the steering axis to the right. The real lesson I learned is that the UFM must be considered as a unit, and correcting just one part will not t fix everything and may even make things worse. This is picture 377 It then occurred to me that rather than trying to correct the steering column rotation, it would be easier to correct the fork. I put a 1/2 rod in the top fork hole and placed it not through the bottom hole but just under 1/16th inch in a direction to correct the rotation and presto, there was no misalignment. So, I think I will try a couple of things in increasing order of difficulty, and if I am lucky, one will work satisfactorily. For the fork rotation, I will just put it together and ride it, and see if it causes handling problems. If it does, the next easiest thing is to put thins shims on top of the head nuts on the left of the front head below the head bracket. this will rotate the steering axis to the left slightly. Even Phil Irving thought about this: from MPH 378 "Excessive tightening and/or overheating is likely to cause permanent deformation of the bolt bosses, and subsequently going round the bolts and again over-tightening them eventually results in causing one or more of the bolt bosses to co llapse. The one most likely to be affected is at the near side of the front cylinder which apparently runs hottest, but any of the others might suffer in a particularly bad example. Besides being squeezed down below its original height, the boss may have cracked away from the top fin, but the head may still be usable. This sort of defect, though rare, is sometimes found on engines fitted to hill-climb cars without the head brackets in place. It may well be that the absence of these components allows the bolts and bosses to deflect outwards, thus causing the cracking of the top fin. If such an engine is being put back into a standard machine, it is essential for the tops of all the head nuts to be parallel to the joint face which will necessitate packing up the low nuts wit h thick washers or shims. [B]This precaution may seem a little finicky, but any slight inclination of the head bracket will throw the steering column out of line by an equivalent amount"[/B] (My emphasis here). Finally, if that is not satisfactory, I can fill and re-machine one of the 1/2 holes in the fork to move it that little bit necessary to correct the steering axis. this would be a fix that would be useable for another machine if the UFM ends up with its correct engine someday. I will not worry about the two lower oil tank mount holes since these fit the tank as they are and moving them would cause problems. As a bonus, when I reassembled the headstock to the tank, the petrol tank now fits easily, even though I did not completely correct the rotation of the bosses. They improved enough that it is not a real problem, especially if they are done first, before the rear tank bolts. the outer race of the bottom taper bearing also fits better than it did before the torture, and is centered in the pocket with the correct interference fit fore and aft. Though some stretch exists at the sides, it is within the gap filling powers of the Loctite supplied with the Patzke kit. Finally , I attached picture 380, since it shows an interesting thing about the oil tank holes in the headstock of this late 1948 B[ATTACH=full]2919[/ATTACH] [ATTACH=full]2920[/ATTACH] [ATTACH=full]2921[/ATTACH] [ATTACH=full]2922[/ATTACH] [ATTACH=full]2923[/ATTACH] . The front 3 seem to have been drilled off the cast bosses centers quite a bit, which would rotate the oil tank up at the front a little bit. This might affect the angularity of the rear head mount bracket slightly, though I suppose this was all done in a fixture. I can't see any real problems, as I am not sure it would affect the trail, but interesting. So, all in all, a very informative exercise for me, and I can get back to other things awaiting attention, like the RFM and brakes. Ron [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Tank mounting misalignment
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