BSA B50 -500 APG Build

[Old Scrambler]

The dyno prints are a very nice read-out for helpful info......I wish I could get my motor to turn that fast 

You already know you will be going faster in 2013 with that extra HP you just found, and going straight down the course instead of that flag-catching angle of attack

In a few weeks I hope to start fitting some streamlining to my Cub.......trying a fairing from an Aprilia RS125 to stay as narrow as possible in the motor area.

[hotrod]

Looking at your dyno plots your torque peak is around 6500 rpm. That is where the engine is breathing most effeciently (highest volumetric efficiency.)

Is that engine set up so you can easily tweak the cam timing by advancing and retarding the cam a degree or two to see if it likes one of those changes at higher rpm?

Larry

[Koncretekid]

The short answer is no.  I can change it, but I have to remove the outer timing cover, the inner timing cover, including pulling a pin to allow cover to be removed over transmission shafts, removing the timing trigger which is on a taper with no key, removing the crank pinion nut, and rotating the pinion gear to one of 5 positions (with a selection of 3 offset keys), then reassembling the lot (no gaskets on cases except RTV silicone, so lots of cleaning), torquing the pinion nut, assuring that a seal and an o-ring  that feed oil to the crank are not disturbed, and resetting the timing.  Worst of all, the only way to know what you got is to degree the cam timing after these changes.  I will be doing so this winter to find out if something has changed and I will catalogue the 5 positions for future reference.  In any case, I wouldn't be able to do it during a dyno session unless I wanted to buy the dyno!

This is why I'm curious to know what the cam timing is for Nascar or high performance Hemi motors running at Bonneville as a starting point.  My cam was designed for road racing standard long stroke B-50s and not for maximum hp.

[wobblywalrus]

Tom, a truly well tuned engine often has very unimpressive specifications such as valve lift, duration, compression, etc.  The parts it has all work in harmony with each other.  Cams are especially problematic in this respect.  Too much of anything in camville will reduce performance rather than help it.

The Triumph 865 cc engine was pretty worn and ragged when the final dyno work was done to develop the intake and exhaust.  It was at 109% volumetric efficiency as dynoed and as calculated by PipeMax.  It is likely it would be at or over 110% if it was fresh.  A 110% VE is all I ever expect from an air cooled engine with side draft ports.  Development was finished.  It was as good as I could make it with the resources I have.  I verified this with others.  They said it was a good engine.  The purpose of saying this is not to brag.  It was essential for me to be at this place so I could go to the next step.

Now I compared the engine specs to PipeMax recommendations.  The cams closely match PipeMax recommendations.  The lift is .388 intake and exhaust.  Pipemax recommends .385 maximum and .389 maximum effort lifts for the intake and .372 and .338 maximum and maximum effort for the exhaust.  The minimum lifts to prevent choke were .350 and .388 for intake and exhaust, respectively.  The cams exceed these.  The program said the "Best estimate RPM operating range from all Components = 6304 to 8304"  This corresponded well with the shapes of the dyno curves.  There is a bunch more cam, valve, and flow info on the Pipemax sheet and  have yet to figure it all out. 

PipeMax showed me that a computer based program can give realistic results that match a good running motor.  In reverse, can it be assumed a good motor can be built by following guidance from a program?  Probably.  PipeMax is written for an advanced amateur or professional and it is hard for the regular guy to figure out.  Some sort of virtual modeling program with a good tutorial might be what you need. 


           

[Koncretekid]

Bad News!
I'm a little embarrassed to have to post the following photos, especially in light of the recent frame rule discussions going on under SCTA Rule changes.  But it is a real eye opener to me and maybe to all.  We build our projects according to rules and what we consider good practice and hope for the best.  I used many resources before starting my build, but apparently I made some mistakes in judgement.  My main resource for building my frame was John Bradley's "The Racing Motorcycle - A Technical Guide For Constructors."  I assumed that a straightliner would have less in the way of stress than a road race bike, and so used the bare minimum of frame material, which is 1020 CREW (cold rolled electric welded) 1" x 16 gauge (.060").  Mr. Bradley did not use this type of tubing, but he cites having spoken to others that have with no apparent problems. Well the following photos show what happens with such tubing in a rigid framed landspeed bike.
The first photo is the finished frame after painting.  Does it look well designed?  I thought so.  The second photo shows the first problem that showed up - a broken strut that supports only the gas tank, rear fender, and tail section.  I more or less considered it a fluke and replaced the tube just before going to Bonneville this year.  The next photo shows a broken frame member at the lower motor mount that showed up after Bonneville.  And upon further inspection, that strut that I replaced was broken again.  Not to mention that the rear inner fender (Honda CB350) was broken in at least 4 places.

[Koncretekid]

I'm not finished yet!

Next, I started looking closely at all the frame members, and this is what I found.  The rear sub-frame that supports the tank, rear fender, and rear bodywork has two more cracks.  And worst of all, there is a crack in the mainframe just ahead of the seat hoop.  This last one is the real killer.  The others are replaceable. You will also see other lines but they are paint lines where I have touched up the frame after repairs or having added tabs, etc.  Looks like it's back to the drawing board, or at least to a full rebuild of the frame, using better quality, heavier wall tubing.  

[thefrenchowl]

Hum, I feel your pain...

But heavier tubing doesn't equate to better tubing sadly... Nor more bracing equals less risk to break...

And it's hard to give advise on frames and how to build them, they're all different and have variable loadings depending on engine, revs, fairings and such.

I did ask meself the question (is my bike too light???) when I was on the Salts in 2011 and seeing a lot of heavy builds that somehow goes against the grain of what I think I know!!!

Patrick

[tauruck]

Frequency vibration?. Maybe some bigger gussets to relieve the stress. I don't think it's the material you used but my only experience is rigids on the road.

[saltwheels262]

well,,
the frame was basically in "1 piece" the last time it came to a stop after a run.

there are some stars you can thank that it did not become 2 pieces and dump you off.

bf

[superleggera]

I used to build chromoly frames for the Ducati motorcycles racers and street enthusiasts.  Every new frame was either PT (Liquid Penetrant Tested) or MT (Magnetic Particle Tested) inspected before it was painted/coated and assembled as a motorcycle.  It is cheap to do.

One thing that I learned after 25+ years of automobile racing -- inspect the frame / suspension after every single time it is run along with your basic "nut&bolt" inspection.  At the end of each racing season, all stressed components are disassembled and sent out for testing irregardless of visual inspection.  You can't see small hairline fractures that could bite you later.

Glad to see you caught the damage now instead of discovering it later when at speed.  When torn down and paint removed/repaired, send it out for PT or MT testing to make sure you have no surprises later.  Cheap insurance especially if you discover additional problems that can be easily repaired now.

[Freud]

Listen to superleggera. He's been there and done that with high tech machines.

His advice comes w/o a dollar price but carries validity that sometimes even money doesn't buy.

FREUD

[wobblywalrus]

Wow.  I've never seen anything like that on a bike.  We have problems like that on steel bridge members.  Cracks midway along the girders, beams, etc are often from vibration induced metal fatigue.

[manta22]

The Porsche 917 tube chassis was built with small holes that connected all the tubing together on the inside. A Schraeded valve and pressure gauge allowed the tube chassis to be pressurized so checking for cracks became a simple matter of looking to see if the pressure has leaked down.

Regards, Neil  Tucson, AZ

[Nortonist 592]

Wow.  I've never seen anything like that on a bike.  Cracks are often from vibration induced metal fatigue.

Its a British single.  Its cousin the Victor redefined vibration.  If you ever had any fillings in your teeth you should check to see if they are still there.

[Glen]

Pressurized tube chassis is not new, has been around for more years then I care to think about. It's a great way to test and not a difficult item to add to any build old or new. Between seasons it's best to tear down the car as far as you can and replace things that are needed or even look like it could be a problem later. In air craft it was easy to find leaks when everyone smoked, you could see it ( nicotine () around rivets and seams on the fuselage.