BSA B50 -500 APG Build

[JimL]

Congrats, Tom.  That is a really good number!  Have a successful time at BUB, and we will be watching your results!

JimL

[SaltPeter]

Brilliant  roll on Bonneville 

Pete

[wobblywalrus]

That is a big number.  Good job.  We will see you at BUB.

[Koncretekid]

Thanks for the complements.  I took the sump plate off the bottom of the fairing today and this is what I found.  These are motor mount plate bolts and nuts, grade 8, all with lock washers and mostly self locking nuts. I expected the oil, but not the other parts. This was after just three runs at Loring (since the sump plate was off for clutch repairs).   Most of the other 12 mounting plate nuts were loose, as well.  Guess I didn't check tightness often enough.  Maybe I should consider a different balance factor.

I had just posted a check list on "things to do before a race" on this forum the other day and of course, checking for loose nuts and bolts was one of the things on the list.  "Do as I say and not as I do."

Tom

[roygoodwin]

safety wire

[wobblywalrus]

Stuff rattling loose is often due to something being compressed or stretched beyond the elastic deformation limit.  Things I look for are washer compression, bolt or stud stretching, or compression of the parts clamped together by the bolts.  The bolts are strong steel and the clamped parts are weaker aluminum.  Compression deformation would probably be in the aluminum.

       

[RidgeRunner]

Stuff rattling loose is often due to something being compressed or stretched beyond the elastic deformation limit.  Things I look for are washer compression, bolt or stud stretching, or compression of the parts clamped together by the bolts.  The bolts are strong steel and the clamped parts are weaker aluminum.  Compression deformation would probably be in the aluminum.

       

     Good points.

     In 35 years on the RR I saw a lot of parts rattling around with the safety wire still intact.  Mostly from the fastener changes, locomotives not having a big percentage of aluminum.

     To me the 2 biggest values with safety wire are: #1 bringing out the human nature tendency to double check the tightness of the fastener one final time before starting the wiring process;  #2 The wire keeping any subsequently loosened parts somewhat together and away from places where they might cause further damage.

                                  Ed

[manta22]

A while ago I read an article about vibration testing various types of fastener locking devices. They tested these bolt/nut fasteners in a Junkers machine-- it moves two plates sideways in shear while the fastener is installed in a through-hole in the two plates. A motor vibrates the plates in shear at a rapid rate and after a time the fastener is checked for tightness.

The upshot of this test was that common lock washers are worse than useless. Different types of locknuts had varying degrees of effectiveness. Torquing the fastener to the correct tightness was one of the most effective ways of retaining the fastener under vibration. I forget what Loctite did in that test.

Regards, Neil  Tucson, AZ

[manta22]

Here is a reference to some of those tests: http://www.boltscience.com/pages/junkertestvideo.htm

Regards, Neil  Tucson, AZ

[Koncretekid]

safety wire

Roy,
I agree with you on this one.  I have a total of 13 bolts securing the motor including the 4 plates that fasten to the frame crossmembers.  Both the nut and the bolt head need to be drilled.  Bolts heads are easy (straight thru) but corner drilling of grade 8 nuts is not.  I therefore need to drill 26 holes.  I generally get about 2 holes to a drill bit, even when I use an end mill to start a flat and a center drill to start the hole.  Bits break off when exiting the other side.  This is a poor excuse for not doing it.  The bigger question to me is why did they get loose?  It is possible that I forgot to tighten them because I did have some trouble getting all 13 to line up after I re-built the frame.

For this round, I have re-tightened all the nuts to 30 ft-lbs and used blue Loctite.  If the problem continues, I will have to bite the bullet and drill all those suckers.

Stuff rattling loose is often due to something being compressed or stretched beyond the elastic deformation limit.  Things I look for are washer compression, bolt or stud stretching, or compression of the parts clamped together by the bolts.  The bolts are strong steel and the clamped parts are weaker aluminum.  Compression deformation would probably be in the aluminum.

      

Bo,
I use grade 8 x 3/8" bolts and nuts with washers on the aluminum and lockwashers.  If all are tightened to 30 ft-lbs in an oily condition (would Loctite act like oil when torquing?), a clamping force of 6100 lbs should be achieved, or around 6750 lbs with the fine thread ones.  The area of a plain washer would be around .497 in sq. which would require over 17,000 lbs of compression to reach the yield point (35,000 psi) of 6061-T6 aluminum.  Using a lockwasher and omitting the plain washer, the area would be about .301 sq.ins, which would resist a compression of 10,535 lbs.  Of course, with a slightly oversize hole in the aluminum plates, I would be getting close to the yield point of the aluminum.  I think it likely that I simply failed to completely tighten the nuts as opposed to overstressing the aluminum.

And to your reply, Ed, I agree that the exercise of safety wiring is just a darn good practice to make sure you really did tighten those nuts and bolts.

And Neil,
I just got your post while writing this one.  I guess what happened sort of reinforces the results of that study.

The following photo shows a grade 8 nut and bolt drilled as I have found to work.  If you look closely, you will see that the drill bit is broken, which happened as it exited the opposite corner of the nut.

Tom

[bak189]

Back in 2002 we ran our Rotax (Can-_Am) powered 125c.c. with front wheel covers (time only at SCTA/BNI) BIG, BIG handling problems with even a very small cross-wind.......Ran a Dustbin on the same bike (time only) Yes, there were handling problems with a cross-wind, but not something I was not able to cope with.....
the bike could not be ridden at speed with the wheel covers......May work better on a heavier bike, but not on our small 125c.c..

PS.  The 1973 125c.c. Can-Am bike also tried the long tail....looked great in the tunnel, did not work on the salt......However, they are now being used on the larger displacement bikes with success.....just wondering if that may be some of the problems regarding some of the bad crashes of late.............................

[Freud]

bak.....that 125 was one of my all time favorite bikes.

The fotos were SO CLEAN.

FREUD

[manta22]

Tom;

Yes, Loctite does act as a thread lubricant when torqueing fasteners.

Regards, Neil  Tucson, AZ

[hotrod]

Regarding locktite and vibration you might look at the chart on page 4 of this pdf doc.

http://www.loctite.com.au/aue/content_data/133403_LT_4985_Threadlocking_Users_Guide.pdf

[Koncretekid]

I find it interesting that none of the tests seemed to proceed beyond 1,000 or so cycles. And we have motors that vibrate at the tune of 8,000 or more cycles per minute.  It would be interesting to see what even Loctite would do after a million or so cycles, as I would get to a million in a couple of hours of running.