Bugatti T72 Bicycle engine.

"Trevor Slattery, ACTOR" (anacostiabikecompany) 04/07/2015 at 12:10 • Filed to: None

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12.60cc, single cylinder with gear driven OHV and a compressor. 10,000rpm redline.

http://www.bugattirevue.com/revue29/t72.ht…

PS9 > Trevor Slattery, ACTOR 04/07/2015 at 12:11

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See? Even Bugatti had to start somewhere.

ACESandEIGHTS > Trevor Slattery, ACTOR 04/07/2015 at 12:22

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Can't trust it. French company, Italian name. They're trying to mislead me somehow.

On the real though, that is a quality bolt-on bicycle-to-moped conversion. Or at least it looks it. The extra chainwheel and bracket cover/ ummm... crank-reinforcer etc. seem like a complex retrofit. But I imagine it probably involved removing a single pedal and sliding everything on over the crank, then bolting down. I'll bet someone skilled could get it set up in 15 minutes.

I'd buy one if it was still 1946 or whenever this sort of thing was popular.

Took another look at it... can you put a freewheel or something on the human-powered side of those chainwheels? You know, so the engine doesn't pull your pedals and feet around like an unwilling fixie?

Last note: I like that whoever restored it has put hex head bolts into it to keep it serviceable. I was dealing with phillips-head crankcase bolts as recently as like 1991 and I pity anyone who would still try to use them.

Trevor Slattery, ACTOR > ACESandEIGHTS 04/07/2015 at 12:25

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Amazing piece of engineering. Who thinks to make a roots supercharger that small?

Ugh...now THAT is going to be some machine work.

RamblinRover Luxury-Yacht > Trevor Slattery, ACTOR 04/07/2015 at 12:29

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If the overall driveline ratio is about 1:3 (about what it looks like), then 10,000RPM on a 26" wheel would make for over 250mph. In other words, in actual service, these things would be doing about 2000RPM, and the engine is comically overbuilt.

Trevor Slattery, ACTOR > RamblinRover Luxury-Yacht 04/07/2015 at 12:45

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A quick count gives a 10t off the crankshaft and a 48t at the pedals. Which would bring the rev's down to 2,000rpm. But I look at this crank and assume there is some type of further gear reduction/clutch setup in there. And to say it is overbuilt is an understatement! One does not need DOHC and a supercharger on a 12.66cc engine.

RamblinRover Luxury-Yacht > Trevor Slattery, ACTOR 04/07/2015 at 12:54

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The two large sprockets are riveted together. There *is* a freewheel or clutch on the crank, but it doesn't have anything reduction-wise it can do. Therefore, unless there's a reduction in a transmission in the rear hub (possible for a bike of this vintage - no more than three-speed, though), the ratio is that of the motor drive sprocket to the hub driven sprocket, or about a 1:3 underdrive. The pedal sprockets doesn't enter into it - same chain rate in, same chain rate out.

If the rear hub has a transmission, it's not doing more than cutting it in half, I'd reckon, which still means 4000RPM for 50mph in low gear.

Mr. Ontop, No Strokes, No Smokes...Goes Fast. > Trevor Slattery, ACTOR 04/07/2015 at 13:06

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You forget where you are on the internet ,man. this is OPPO! We need DOHC and superchargers on EVERYTHING!

Trevor Slattery, ACTOR > RamblinRover Luxury-Yacht 04/07/2015 at 13:07

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Yup, right you are on the sprockets. And while I am sure the engine was good to 10k+ I assume that it was most likely rev'd much lower than that in general use. Apparently some type of reduction gearing was indeed used.

http://www.users.globalnet.co.uk/~pattle/nacc/a…

RamblinRover Luxury-Yacht > Trevor Slattery, ACTOR 04/07/2015 at 13:10

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I missed the worm drive *in the crankcase*, because I wasn't paying attention. That's at least a 1:4 reduction combining to a minimum 1:12 or so, which makes the numbers make a lot more sense.

Trevor Slattery, ACTOR > RamblinRover Luxury-Yacht 04/07/2015 at 13:11

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The thing is an engineering feat, I will say that much for it.

greenagain > Trevor Slattery, ACTOR 04/10/2015 at 09:06

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Amazing. EB was an awesome brain.i saw over a dozen Bugattis at the Mullin Museum and I walked out dizzy, and drooling.