The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: 900triple on 28.04. 2011 13:38
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Help required!
I've got my plunger A7 off the bench for the very first time and unfortunately the plunger units seem to be mis-aligned. The plunger units wont move when I try to compress them and appear to be out when I look by eye.
If they are out - any tips on how to get them back in line? The bike is being built up from bits and the frame looked okay when I got it but obvioulsy isn't.
Any advice would be gratefully received...as would be a good frame if this one is knackered - although I hope it can be fixed.
Cheers
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G'day 900,
do you mean that when looking from the rear, one side is higher than the other or not parallel? My original '51 frame has one side higher. Thought about fixing myself for about 1 nanosecond. Ask the local bike shop who is the best to send it to.
Cheers
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Mines the same right side seems about a 1/4" lower,, perhaps its designed that way for wheel torque
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Not parallel - I'll post some pictures when I get home from work - can't do it on the work puter.
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are you certain that you have fitted the plunger springs the same both sides, heavier coil to the bottom of the wheel fork, and lighter to the top?
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Do you have all your spacers in the correct places ?
Also measure each of your springs ( with out a load on them ) for size
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Its the plunger units themsleves which appear to be not parallel to each other. The assembly is correct (big spring at the top - the smaller (rebound) spring at the bottom). I am guessing that when the frame was spilt by the previous owner in order to ship it to me then the rear was twisted slightly.
Still having problems with my own PC so can't post a photo. Sorry. I am going to measure via a laser and straight edge the relative position of the top and bottom of each plunger to the centre line. This should give me a clue as to which unit is off. Maybe both if I'm unlucky!
Once I can determine that then it should be relatively easy to bring them back parallel. I hope.
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Have you sorted this out?
I had this trouble. It was the plunger mounts that were misaligned due to many years with a side car with previous owners. I adjusted mine by getting the frame vertical measured off the front yoke, then using a length of scaffold pole to bend the frame back ever-so slightly. I used a cheap laser level for the measurement.
I agree with previous post that the springs or spacers look wrong - if the frame was wrong the bottom plunger frame mounts would be different distances from the floor.
Stu
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Well thank goodness my computer is back working...had to buy a new one!
Anyway - here's the problem I think. When the brake plate is fully located on the proper side the plate is not parallel to the plungers. When I put it on the other side...same. Looks as if the plunger guides are twisted. I have measured the distance btween the tops and its 250mm and the same at the bottom. So they appear to be parallel.
If it is the guides then is there an alternative to fighting with them to get them out and replacement ones back in - not something I'm looking forward to to be honest.
Thoughts??
Also I'm in the proce4ss of fitting the mudgaurds. Not sure about the rear. Anyone know where to source a rear in the same shape as the front...?
Cheers
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Any ideas??? *eek*
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Hi 900,
You dont add a name to your posts ????
Anyway, have you set up the frame vertically, headstock /saddle tube?
If so and the plunger pins are vertical then its the wheel /axle lugs are bent
If the frame is vertical and the plunger pins arnt then the back of the frame is twisted
HTH
John O R
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These units are quite often bent but I havent seen a set this bad before.
What you need to do it dismantle them and you will have to heat them and straighten them. When you have them apart place them on a flat surface like in the attatched pic, the tube the shaft goes through should be parallel to the surface.
Get a bar the right diameter to go through the tube. You will need a oxy set and a good vice. Put the bar through the tube and heat the section in the middle of the lug then put the bit where the axle goes through in the vice and twist. You might have to do this a couple of times to get them right.
Wear a pair of gloves and eye protection, let the lugs cool slowly, dont dunk them in water.
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Also I'm in the proce4ss of fitting the mudgaurds. Not sure about the rear. Anyone know where to source a rear in the same shape as the front...?
When I did my '52 A10 up, I got a new rear mudguard off of Burton Bike Bits - the hinged one. You need to drill your own mounting holes in it, though.
I had it for a few years before fitting, and found it a bit bannana shaped. Managed to get it on with a bit of coaxing, but that's something to be aware of - trying to fit 'new' cycle parts onto an old frame. So not really sure if I'd recomend them. Maybe I just got a 'Friday afternoon special'. They were at 138 Waterloo St., Burton on Trent back in 2003, don't know if they're still there. The email was [email protected] and phone was 01283-534130.
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I've looked around the garage and found another set - had the miller at work check the run out/squareness of the inside of the spindle slot to the tube and they were both 2mm more or less exactly but opposite ends. The inside of the spindle slot has now been machined square to the plunger tube to within .001". I've assembled the units without the springs and the sprocket is perpendicular and they slide up and down together nicely with the wheel and spindle in place.
Looks like problem solved.
Ta for all advice
Alan