Author Topic: BSA B50 -500 APG Build  (Read 460887 times)

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Offline Koncretekid

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Re: BSA B50 -500 APG Build
« Reply #330 on: July 28, 2012, 06:57:04 AM »
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.
Bo,
Problem is that the case is only 3/16" thick and the bearing plate I used suggested drilling and tapping oversize to 1/4-20.  There's just not enough aluminum to tighten a 1/4-20 screw properly, so I depended on Loctite.  Just before my record run, it had come loose in the pits and we had to re-install them with red Loctite, but the threads were beyond their "best before" date and failed.

Also welding was suggested, but then I would have had to split the cases to change the front sprocket.  I just might have to do that at Bonneville.........

I've looked at a lot of possibilities.  Timeserts look the best, but are too long and require a counterbore that would remove even more of the case, leaving only about .100".

The solution I've chosen was suggested by "Beat" from Switzerland on the B50.org site.  Add six extra holes in the bearing plate and make steel inserts that press in from the back side.  Eleven allen head socket screws with the underside of the head chamfered, and drilled to accept lockwire.

The first photo shows an original BSA plate with only a seal; no bearing, my destroyed plate, and a new one from Mark Cook at PES in England who specializes in B50 parts.The second photo shows the small inserts I made and the screw.  The third photo shows drilling and chamfering the new holes in the plate, and the forth shows the finished repair.  You can also see the nice welding job on the case that my friend Steve did.
We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!

Offline Koncretekid

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Re: BSA B50 -500 APG Build
« Reply #331 on: July 28, 2012, 07:08:53 AM »
Collateral Damage!

When the motor overrevved, it bent a valve, tappet, and pushrod.  I also discovered a broken frame member in an unusual place - - a strut that simply supports the subframe that supports the gas tank and the rear fairing.  Why?

I had some longer pushrods that just needed to be shortened 1/8".  I chucked them up in the lathe, cut away the chrome moly tubing, then gave it a whack with a 2 lb. mall, and presto, shorter pushrods.

Also shown is the Quaife transmission versus the BSA unit.  Beautiful piece of work, with close ratio gears which should help in the 3rd to 4th gear shift. The other BIG advantage of this transmission is that high gear runs on needle bearings and the clutch is on splines rather than a taper.

New valve is on the way, tappets and clutch chainwheel were sourced from British Cycle Supply here in N.S.  Motor is back together, sans the head, and re-installed in the frame.  I cut out the damaged frame strut, re-fabricated, and had Steve weld it back in place.  Bike is well onto the way to being back on the track.  Good thing, because today I pick up my daughter, son-in-law, and grandchildren at the airport for a couple weeks of  R & R (with perhaps a little bike re-building thrown in)!
« Last Edit: July 28, 2012, 07:10:55 AM by Koncretekid »
We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!

Offline wobblywalrus

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Re: BSA B50 -500 APG Build
« Reply #332 on: July 28, 2012, 11:26:24 AM »
Tom, it looks like the bike is coming together well and far better than I could do.  The taper between the transmission mainshaft and the clutch basket was always a problem for me.  I sure wish I knew about the Quaife gear cluster.

The frame flexes when it absorbs energy from the vibrating engine.  Cracks in weird places result.  Simply butt welding the tubes together at the crack can be problematic.  It cracks again near the weld.  Usually I slide a sleeve into the broken section and weld the broken tubes together around the sleeve.  Then, about an inch or so on each side of the weld, I drill 3/16 holes through the tube and partially into the sleeve, but not through the sleeve.  Then, I tack the tubes to the sleeve at the holes.  This distributes the stress.   

Offline Peter Jack

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Re: BSA B50 -500 APG Build
« Reply #333 on: July 28, 2012, 12:03:23 PM »
Really nice fix Tom. Well done!  :cheers: :cheers: :cheers:

Pete

Offline Old Scrambler

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Re: BSA B50 -500 APG Build
« Reply #334 on: July 28, 2012, 12:33:45 PM »
Great Fix :cheers: :cheers:

Suggestion:  Add a small triangular brace to the near 90-degree corners of the rear frame-section.  One little corner brace was added by Triumph to the neck/frame area of the Cub to change a street bike into a Trials competition bike - Mountain model.

That is a very nice tranny.....and SHIFTER PLATE 8-) 8-) 8-)

I am not sure but you may be able to "flip" the plate to change your foot-control direction.
2011 AMA Record - 250cc M-PG TRIUMPH Tiger Cub - 82.5 mph
2013 AMA Record - 250cc MPS-PG TRIUMPH Tiger Cub - 88.7 mph
2018 AMA Record - 750cc M-CG HONDA CB750 sohc - 136.6 mph
2018 AMA Record - 750cc MPS-CG HONDA CB750 sohc - 143.005 mph
2018 AMA Record - 750cc M-CF HONDA CB750 sohc - 139.85 mph
2018 AMA Record - 750cc MPS-CF HONDA CB750 sohc - 144.2025 mph

Chassis Builder / Tuner: Dave Murre

Offline bones

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Re: BSA B50 -500 APG Build
« Reply #335 on: July 29, 2012, 02:39:40 AM »
Hey Koncrete
   Fabulous job on the body. And congradulations on the speed
   Do you know what caused the weave? Did it happen only once?
  Have you thought about a belt drive for the primary? No need to seal for oil and only a ninimal cover.
  My mate uses a belt an his vincent and has given no problems.
 See you at Bonneville
  cheers   Bones

Offline Koncretekid

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Re: BSA B50 -500 APG Build
« Reply #336 on: July 29, 2012, 01:15:37 PM »
Bo,
I considered repairing the broken tube, with slash cut insert and an upper and lower insert with rosette welds as you have described.  But my welder said " I would just replace the tube", so I did.  Not really any more work. BTW, the Quaife was only made for the single cylinder BSA for a limited time and is no longer available. I scored mine on eBay from Frank Diehl in North or South Carolina which had only been used in two races, according to seller.  However, Nova Transmissions still makes them.

And Dennis,
Gussets are a good idea, especially on tubes subject to moment loads (bending at the weld).  This tube doesn't seem to be subject to that, but probably vibrated  and fatigue failed due to stress riser at the tabe welded on for the chain guard.  And I can flip the shift plate to reverse the pattern.  I set up all my race bikes in the reversed  or GP shift mode, 1 up, 3 down.  I sometimes get confused on my road bikes, some left, some right, and all standard shift.

Bones,
I questioned several experienced minds at Loring about my weaving problem at about 125 mph, including Fred Vance.  I was told that fairing equipped bikes can be sensitive to overtight headstock (not a problem on mine) and height.  I raised the front end 5mm, and approached the timing lights less aggressively on the next (and record) run and did not get the weave.  However, all minds were unanimous in suggesting I get rid of the bias ply rear tire with the radial front.  Problem is, 120 width is my limit, and I can't find a 120 width rear radial tire.  The solution is to run a front tire on the back, but in the reverse direction.  I will do that for BUB.  It will also be 70 series instead of 80, so 12mm smaller  which lowers the rear.  As far as using a belt primary, I've heard that big single cylinders eat belts.  Also, the clutch has 25 1/8" diameter rollers which will flat spot pretty easily.
We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!

Offline RidgeRunner

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Re: BSA B50 -500 APG Build
« Reply #337 on: July 29, 2012, 09:54:19 PM »
Not the problem with yours I know, but I'll add that it doesn't take a fairing to make a bike with an over tight headstock weave.  My un faired BB 34 picked up a weave when I over tightned the headstock bearings on re assembly once, weave went away when I backed them off just a bit.

Ed

Offline wobblywalrus

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Re: BSA B50 -500 APG Build
« Reply #338 on: August 16, 2012, 12:50:24 AM »
Tom, in the early days I ran a bias ply front tire with lots of air pressure as per common practice.  A few years ago I switched to a radial front tire and I ran it with Metzeler's 36 psi recommended pressure.  My goal was to increase the pneumatic trail.  This change really helped my speeds.  The bike tracked much better with less deflection due to ruts and other surface irregularities.  It also held a line much better in side winds.  I was more confident so I tucked in lower.  Also, I went in more of a straight line.

Offline wobblywalrus

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Re: BSA B50 -500 APG Build
« Reply #339 on: August 27, 2012, 04:47:15 PM »
Tom, check your e-mail.

Offline Koncretekid

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Re: BSA B50 -500 APG Build
« Reply #340 on: August 30, 2012, 01:12:37 AM »
Mixed results at BUB with a decent ending.
1st photo is the flats on Sunday after the rain.
2nd photo is Ed, my crew chief, and me.
3rd photo is the flagstand I ran into.  Note the wheel track and the broken pole.
4th photo is a piece of the flag pole which blew in thru my air intake.
 
1st downrun to check out the course: 120 --- too rich, leaned out for 2nd run.
2nd downrun: 129
return run: carburetor fell off
3rd downrun: 131
return run: 137 in the KM, then ran over the flagstand at the end of the timing mile.  Broke off the flagstand but missed the mile timing light (literally -- see photo)  Found pieces of the PVC flagstand in my fairing and in my motor where my air intake cut off the flagstand.  Lucky to not have a major get-off.
4th downrun: couldn't get it into 4th gear: 118 mph
5th downrun: 131
return run: 135  :-D

Tomorrow we tear down at 7:00 AM, then back onto the track

Tom
We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!

Offline Graham in Aus

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Re: BSA B50 -500 APG Build
« Reply #341 on: August 30, 2012, 05:46:23 AM »
Great write up Tom, and what a journey you are on! Well done on staying upright and 135mph!

Ossum!  :cheers:

Offline Jon

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Re: BSA B50 -500 APG Build
« Reply #342 on: August 30, 2012, 06:30:27 AM »
Congratulations Tom, what's your previous best?
Is the teardown in the impound?

Those mile markers must be magnetic.

Cheers
jon
Underhouse Engineering
Luck = Opportunity + Preparation^3

Offline JimL

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Re: BSA B50 -500 APG Build
« Reply #343 on: August 30, 2012, 12:05:54 PM »
Really good speeds, and glad the engine stayed together!  Were you fighting some wind, or was the front end floating away?  I nearly got the 1 flag at 2010 Speedweek, when the lack of front weight let the APS fairing blow the front wheel away.  Thats about the point where we are building enough speed to experience the condition.

Give me a call sometime, if you still have my number.

Congratulations  :cheers:

JimL

Offline Koncretekid

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Re: BSA B50 -500 APG Build
« Reply #344 on: August 30, 2012, 06:58:53 PM »
Jim,
It was mostly pilot error.  I was trying to get my shifts right, watching the tach, and not paying enough attention to staying in the center.  When I noticed I was drifting (16 mph crosswind), it was too late to correct.

After getting torn down for measuring this morning, we went out and bumped the record up 1 mph! 134 and change.

Tom
We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!