The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: roadrocket on 15.10. 2020 11:31

Title: Flywheel installation
Post by: roadrocket on 15.10. 2020 11:31
Hello folks,

I have now had a chance to use the family oven to heat the crankcases and thus renew drive side bearing and timing side bush. I also heated the flywheel and put the crank in the freezer. But I don't seem to have the knack to get the flywheel started on the crank. Is there a proven method? It is a later thick flange crank with radial bolts (new ones ready). The flywheel was only loosely mounted on the crank without bolts when I got it.

Cheers, Otto
Title: Re: Flywheel installation
Post by: Greybeard on 15.10. 2020 11:52
I have now had a chance to use the family oven to heat the crankcases...
Did you have to wait for 'someone significant' to visit Ikea?
Title: Re: Flywheel installation
Post by: roadrocket on 15.10. 2020 12:07
He he, an art museum as a matter of fact ...
Title: Re: Flywheel installation
Post by: Swarfcut on 15.10. 2020 12:21
Otto.  If its anything like a small journal to  fit, it will be like a metal puzzle from a Christmas Cracker. It will only go on one way, and then only when either pressed on or heated to expand and probably also need a bit of a smack to line things up.

 Recent ebay purchase was a SJ crank with the  flywheel held on with 8mm soft nuts and bolts. Never having disturbed a flywheel before this was too good to miss and once unbolted began the Houdini trick. It was not easy, there is a definite knack with the positioning of the flywheel to pass over the  big end and crank web. This crank needs grinding, and although it can be ground with the flywheel in place, I'll reassemble after machining. A nice protective tape wrap on the big end journals will be a must. For your crank I reckon a bit of practice cold should lead the way, then another big heat up and fingers crossed it fits.

 Any thoughts on new fixings for my crank. Originals were BSF? but High Tensile UNF are more readily available and are a finer thread. Downside is they come in packs of 10!  Also used the oven trick today to ensure less violent removal of big end bolts from an A7 rod. Er, well, they did need just a little extra smack with a wooden block......

 Swarfy.
Title: Re: Flywheel installation
Post by: roadrocket on 15.10. 2020 12:51
It's easy enough to get the flywheel on and off the crank, there being a cut-out for this: turn 180 degrees and the cut-out fits with the pointed end of the bob weights, then turn 180 to get in position. But then the interference fit kicks in, and I'm at a loss to get started.
Title: Re: Flywheel installation
Post by: berger on 15.10. 2020 18:22
swarfy they are bsf, I wanted some a while ago so ordered them by part number. they sent me set screws probably off a shelf at B&Q *bash* they soon got them back. I think you might struggle to get high tensile ones the same with long nuts
Title: Re: Flywheel installation
Post by: Swarfcut on 15.10. 2020 19:12
bergs. My thoughts exactly.  Modern high tensile UNF setscrews and nuts from an established industrial fasteners supplier would be my choice, rather than searching out period BSF nuts and bolts.

 Otto. You have the easy part sorted out. Check there are no sharp edges locking the two parts when they come into contact, a polish with abrasive paper to provide a lead on will help. Otherwise its a hotter oven, a week in the freezer for the crank, then a solid support, a bigger hammer and the hydraulic press.

 Swarfy.
Title: Re: Flywheel installation
Post by: berger on 15.10. 2020 19:35
swarfy 6 bolt flywheels go on easier than that thank goodness. I have used the original bolts and nuts with loctite, I did a test with a couple to see how hard it would be to undo them. one with ex NCB stores Loctite 30 years old, the other with 5 year old modern stuff, same stuff stud and bearing fit. the 5 year old came apart with force on the spanner the 30 year old wouldn't budge until heated up. so you know which one I used. good old store job is still coming in handy 30 years later. the things I borrowed are now my stores ;) ps personally I wouldn't put any setscrews in the flywheel , plain high tensile bolts for me