What we think BSA might have done.

[Mark Parker]

I made a video because I got the carbs dialed in pretty well, finally. Added a high tech, phone on a table near my kit, recording of my daughter Nay. Otherwise there are parts with no sound.

I really want to time this bike on a quarter mile. The Firebird as well. I'm curious. There is a drag strip just 6hrs away. Or we can do it with GPs on a GoPro if we could find somewhere. There are probably bits of old highway on farms, if we could find one without cows. Or get permission off council somewhere.


https://www.youtube.com/watch?v=In366P5S8F8

[Mike Farmer]

 

Plenty of airfields around with WW2 runways. Theres prob one not far from wherever you are. The staff will usually (used to) play ball. Try Google airfield near ?

Might cost a couple of squids.

Mike

[DAVE BRADY]

Hi Mark,

That engine sounds really powerful and modern as it roars past.  The drag strip is good idea but how about some 0 - 60, 40 - 70 times as they are probably more realistic and could probably be done legally on the road using GPS. 

Dave.

[Mark Parker]

Mike, old WW2 airstrips are about 4,000km up near Darwin. Sealed highways up there are open speed limit and sealed with less bits of old Spitfires and P40s littering the place. There is an airport near here.

[chaz]

Presumably, as you ,mention Darwin you are in Australia?
as said Airfields are a good bet, here we have Santa Pod drag strip that runs "run what ya brung" events.
the advantage with these places is that there is usually medical facilities available, just in case something gives way.
the other option, is to find a stretch of decent road and get a couple of mates to keep a watch for police presence, we used to use early morning stretches of  a motorway.

[Mike Farmer]

 

I guess by the time you get to Darwin you'll have a very good idea of what it can do.

Seriously Besta luck sir. My daughter is in OZ at the mo, if you see her say hi.

Mike

[Mark Parker]

What makes me curious is the final drive ratio on the 734 is 3.93-1 that distance is about 1/8th of a mile and it's in 3rd by the end of it, probably picked up the gear at about 5,700rpm, how much would it climb on full noise in 3rd? And it's got almost 1/8th mile to go for a quarter. It's used about 7seconds or less so far. How long would it take to reach another 1,300rpm from hitting 3rd? Would it have room? What would happen if I changed at 8,000rpm? How could I get it off the line for the first 60 feet smartly, in more ways than one?

Can people see why this is sort of interesting. If it stays at the speed it may reach, the last 1/8th mile would take about 4.5seconds. But it will pick up speed, just how much would be an interesting thing. A track and timing equipment would be the best way to find what's ultimately possible.

[Nanonevol]

Who is the band on the video? Not bad.

[DAVE BRADY]

Hi,

It is obviously a very torquey engine but could the final ratio of 3.93-1 be a bit high.  Once on song it will probably not make much difference but from a stand still a tooth down on the gearbox could make all the difference - three teeth off the rear sprocket may be easier.
Better standing start but more revs would probably need to be held through the gears.  Are you using a close ratio box?

I have just found this on the Classic Bike Hub.

"The 75mm by 64mm motor typically ran 9:1 compression to produce 42bhp at 6800rpm. Fully fuelled with four gallons of gas the bike weighed nearly 400lb, so its top speed was slightly less than the 100mph mark, with a standing quarter taking 15.5 seconds or so. In 1968, the Thunderbolt would go from zero to 60mph in 7.4 seconds. The twin-carb Lightning of the same year was only marginally quicker – 15.29 seconds to cover a standing quarter mile and with a 102mph top velocity – for all that it claimed to house an extra half dozen horses."

Dave.

[Mark Parker]

Getting off the line is very important in drag racing, but that's not normal riding or something we would ever do, and there are different techniques depending on track and bike. Low gears means more changing which is time, it's not always an advantage. Plus if I can get acceleration readings off the gps from a low speed it's probably good enough for now, it's just this looks like it could get to high 90s or 100 in an 1/8 of a mile and possibly around 7seconds before it needs 3rd gear. In 1971 an 810 Dunstal Commando could pull 11.9 sec @ 114mph. First bike sold to the public that could do a sub 12second quarter. This feels like it could beat that. But would need off the line skills.

Yea, the band is my oldest Daughter Naomi, guitar and vocals, and me on old Ludwigs with an iPhone propped up in front of the kit for the high tech recording.

[Mark Parker]

The 734 30-60 according to the video gps takes 1.95seconds about. The trouble is the only video on that camera is a roll on and it's not pulling as hard as it could at the start. Compounded by not letting it rev. Second is the same. Power needs to be on long enough to get a true picture. Just giving it a hit isn't the same as maxing it out to measure.

[Mike Farmer]

 

Isn there still a Catalina strip at Cairns.

Mike

[Mark Parker]

My son works in Cairns and his family are moving there. It's only 2,773km or something. Lots of drag strips in Qld not down here. I was walking across the tarmac to the terminal in Cairns and the most glorious noise took our attention, the low rpm power of a V12 wide open as a beautifully restored P40 took off near us. Like it was going up an elevator.

[idie]

What is a P40 ?

[Spaceman]

The main fighter used by the RAAF during WW2 - a Curtis P-40 Warhawk. Originally used an Allison V12 engine but some used a V12 Merlin for better high altitude performance.