BSA B50 -500 APG Build

[Koncretekid]

Keenserts are solid threaded inserts.( internal and external threads ).
after being installed they are locked into the material
with on board "pins".
the jergens company might be the manufacturer.

bill

what was the increase in mile an hour with the fairing ?

Bill,
Thanks for the suggestion.  I looked up Keenserts and unfortunately the major thread diameter required is too big (3/8" OD for a 1/4-20 internal) which would break out.  I am going to cut off most of the old case and replace with good part of another broken case.  I'll have to weld up two of the stripped holes and re-tap.

Last year on the open bike at Loring I went 117 mph. This year with same engine but 12 to 1 CR instead of 11 to 1, with the fairing I went 136 with a slight tailwind.

[Graham in Aus]

Some info here, time-serts may need less 'room'

http://www.practicalmachinist.com/vb/general-archive/time-sert-threaded-inserts-76322/

Well done on the speed increase! 

[Koncretekid]

Hi Tom

What type of screws do you use now?  Have you thought about flat head allans as they hold pretty good with the area of the countersink.

And maybe use 10 or 12 in your cover and drill & tap it in a mill if you can so they all line up perfect, then with some thread locker it should be good to go.

Don

Don,
I was using allen head flat head screws with blue loctite, but the case is only about 3/16" thick.  They backed out early Sunday and we re-tapped the holes (not much meat left) and used slotted flat head screws (all we could find in Caribou) with red loctite.  I went out and made the record run (136 mph), then came in and installed a smaller sprocket.  Went back out and that's when we broke.  Thinking now that the screws might have loosened on the earlier run when the loctite wasn't dry, but just didn't get in trouble until we made the second pass.  I do think I'll add six more holes in the new plate and use red loctite. I have a mill-drill and a rotary table, so that should test my skills to make sure the six new holes are concentric.  Should be dry in 5 weeks.

[Koncretekid]

Some info here, time-serts may need less 'room'

http://www.practicalmachinist.com/vb/general-archive/time-sert-threaded-inserts-76322/

Well done on the speed increase! 

Graham,
I have been looking at the timeserts.  Only trouble  is that the case is only 3/16" thick and the timeserts require an .075" counterbore which only leaves about .112" of aluminum left to anchor the insert.  I may call them tomorrow to see if that will work.

[Old Scrambler]

Tom..........Can you add a little 'meat' to the inside of the case?  Timecerts have worked for me but I never tried something that thin.....................maybe more holes?

That bearing is likely not getting any oil when your at speed because of outward forces.  Two single 530 chains held the crank to clutch drive on the AT&SF for Russ Collins on dozens of drag-runs and I think that has a more torque than the B-50.  Maybe something else is going on?

[Peter Jack]

PM sent

[JimL]

Glad to see that 136 number!  This is getting good (and serious)!

Best wishes on quick repairs and some good salt.

JimL

[wobblywalrus]

Tom, something is wrong when six screws come loose at the same time.  A screw is like a spring.  Tightening it stretches it and the tension holds it tight.  The tension stress must be within the elastic limits of the screw metal - and this tension includes the load placed on screw.  In other words, the tension must not be great enough to permanently stretch the screw.  The stretched screw comes loose.

Examine your screws closely under magnification.  Are they stretched?  If so, the repair must include some way of reducing the tension on the screws or using screws that can withstand more tension.

[Nortonist 592]

Congrats on 136!!   Serious number for a 500 pushrod engine.

[DND]

Hi Tom

The U.S. F/H allans have a 82 degree angle and some other screws are 90, check your straight slot ones as you might have 2 different countersink angles that don't match?

If you go to a smaller screw size with 12 you would have more threads into you thin case, maybe a 6 or 8

Can you install a back up plate for more total thread contact?

Also you bike looks really neat plus the cool lemon yellow, been a yellow nut for yrs!!

Don

[Jon]

Congrats on the 136!!

Would it be worth lockwiring them?

Cheers
jon

[JimL]

Thinking about the screwissue.....are those on the left side, and does the engine rotate forward?

When my twin engine coupling failed, the first point of failure was the trans end case bolts backing out and hitting the counter rotataing drive gear.  Only the bolts on the reverse rotation parts were coming loose.  This is a similar seniario to loose lug nuts on a car....only the left side wheels fall off.   Long ago, some cars had reverse thread on the left side wheels...to stop that problem.  This was also done on reverse rotation camshafts on some inline engines.

Maybe your fix is reverse threads.

JimL

[saltwheels262]

tom,
what a great increase in miles per hour.
I'm thinking it was that fantastic shell you put together,
more than the 1 point in cr .
but, unlike the pope, I've been known to be wrong.

bf

[ChrisLenahan]

Koncrete,  To repair the threads you might want to take a look at a Loc-Tite product called Form-A-Thread.  It is an epoxy that once set can take the torque of a grade 8 bolt.  I used to work in a Turbine overhaul shop and we used it as a fix as least once for a helicoil that pulled out of a magnesium housing in the field. Worked great and in an area like you have with limited thickness its will work where a helicoil can't.

[wobblywalrus]

A common mid-season fix is to weld things together.  Of course, the welds are made in accessible places where it is easy to grind them off during the off-season engine rebuild.  I did this with the clutch basket to mainshaft join many times on BSA's.  Perhaps you could put on your best engine sprocket and tack that plate on with a few short welds.  The permanent fix would occur during the long Canadian winter.