BSA B50 -500 APG Build

[Jon]

Looks good Tom

Can you cover in the back rim for less drag, I'm not near a rule book, I thought the front had to be 20% open and the back can be fully covered.

Cheers
jon

[Duck-Stew]

Looks good Tom

Can you cover in the back rim for less drag, I'm not near a rule book, I thought the front had to be 20% open and the back can be fully covered.

Cheers
jon

Front: 25% open, rear: fully closed is ok.

[Koncretekid]

Front wheel is off an XJ600 Yamaha.  Looks good from one side, but those disc mounts look like wind catchers.  So we made up a disc to cover the mounting bosses.  Got a little carried away with the machining.  After which I now realize that the wheel is about the same width as the space between the forks so will have to be narrowed.  Another couple of hours at the machine shop.  Good thing I have a friend in the business!

[RidgeRunner]

     Brings back old memories.  In '71 I leaned on a friend with a lathe to make up an axle to adapt a Honda Hawk wheel to my BSA's forks, real pretty with the Whitworth threads and all.  Only problem was they were RH and it wouldn't thread in.  Build time was running out, I really hated to give him the news but he did up a new one with a smile, no charge for either. 

     Very few do everything 100% on their own, there are a lot of invaluable crew back home represented at every meet.

                    Ed

[Koncretekid]

Because the real wheel does not require cross ventilation, we made discs to cover them.  There is 3" cover to access the tire valve which has 8-32 screws into threaded inserts pressed in from the back side.  The two discs are connected together with 1/2" diameter aluminum spacers which are located to either side of the three spokes to ensure they don't rotate.  After mounting new Bridgestone tires (110/70 ZR17 in front, and 120/70 ZR17 in back), I was pleased to find run-out of less than .020" at the tire surface. 

In all, this years run will be for confirmation of my new frame and welding skills, and refinement of some of the minor items such as crankcase evacuation, increased valve lift, and intake and exhaust length, and the addition of truly round wheels and the rear discs.   

[Jon]

Looks nice Tom.

Any plans to do similar for the front to 80%?
Be a bit trickier to not have the 20% opening being to draggy, maybe a cone coming from the rim beads down to a point that leaves a 20% hole around the hub? Kind of like an exaggeration of the current Aero pushbike rims.

Cheers
jon

[Koncretekid]

Jon,
If you scroll up the page, you will see my front wheel.  I got an answer from BUB regarding open area, which must be 75% of the nominal rim area by their rules.  I made a 9-1/2" disc to cover the brake disc carrier, which is legal.  Your idea is probably better, but I would have to find a 2-1/2" wide rim with a small center to take full advantage of blocking off 25% of the outer area instead of the inner area.  The other consideration is what cross winds will do to the front of the bike as I close up the open area.  I understand that the original CanAm 175 was wind tunnel tested with a full disc front which did improve aero, but had to be removed because it caused a handling problem at Bonneville.

I have been following your diary carefully and I can't wait to see how it works.

Tom

[Freud]

The BIG problem for the Can Am bike was the long tail. It was efficient but killed handling in a wind.

That bike was a lovely project.

FREUD

[Koncretekid]

The BIG problem for the Can Am bike was the long tail. It was efficient but killed handling in a wind.

That bike was a lovely project.

FREUD

I've never seen the long tail version.  Any pictures?

Meanwhile, back in N.S., I mounted the wheels.  They sure look the part - - I hope they solve some of the vibration problems.  But the motor.........

I made up a few intake manifolds for a dyno run next Friday. I can get anywhere from 1" to 6" with these plus the one that is on the bike.  That is in addition to 3" in the head and a 4" long carburetor. So from 7" to 13".

[Koncretekid]

I also hooked up my reed valve crankcase breather and my exhaust extractor (temporary.)  I could get 7-8" H2O with reed valve alone, 12-13" with the breather hose from the reed valve hooked up to the exhaust extractor.  Still not more than 1/2 psi, but at least it may keep the motor from puking oil!

And last but not least - - warm day, cold beer, hot tub...  It's a tough assignment, but somebody has to do it!

[wobblywalrus]

Tom, wrapping the e-pipe before the dyno work can help.  The reason is the insulation helps to keep exhaust temps more consistent between running at B'ville and on the dyno.  The e-gas temp greatly affects the tuned length.  So, keeping the temps closer to the same will make your running tune more closer to your dyno tune.  The exhaust system tuning will affect your intake tuning so the wrapping will help - even if you are not tuning the exhaust.

[Koncretekid]

Thanks, Bo,
I have postponed wrapping the exhaust because I'm not sure if it is optimized.  But I guess I should to keep temperatures consistent.  Drat!  Another variable!
Tom

[makr]

Wow! Tom, I just read this whole thing. Massive kudos for an outstanding build.


BTW; there is lots of great info in this thread. I will utilize some of it.

[Koncretekid]

I made 17 pulls on a dyno before Loring, using different length intake manifolds, jet sizes, my new reed valve crankcase breather and exhaust extractor, and changed the timing once.  Not enough to find any more ponies, but I did get a wider torque and hence hp curve.  At Loring, I was fortunate enough to bump my record to 140.5 mph in the 1-1/2 miles, 132 mph in the 1 mile.  Still accelerating, so Bonneville looks promising.  See you in 4 weeks.
Tom

[Old Scrambler]

Nice work Tom

Topping 140 mph at any length of run-up is a GREAT accomplishment for a B50

Dave is welding and I am getting the last 42 items on my list ready for the trip to BUB.  See you there