Projects 1917/1928/1938 American Lafrance Plymouth V12 Speedster

It was a buddies engine but in my shop for a few years. I lost interest having moved it fairly often. It was complete but stuck. I got the go ahead to sell it and got $600 for it. Went to a youtuber in NC who promptly got it running. So on one hand made me feel good that he has done something with it, on the other, made me feel lazy for not working on it myself as I am pretty sure if I had heard it run I would have bought it from my buddy.

At the time I was tickled to move it one last time and get some space back. I think if I had less on my plate I would have had the desire to do something with it.

 

Damn wish i was lucky enough to have known you. I spent $1200 on mine. It did have the trans, a bucket of extra parts and the speedo and tach which are gorgeous though.

 

Just found this thread. Awesome build. Can’t wait to see it finished. Was thinking of going chain drive on my build as per the original, but decided if would be too complex without some period corect parts.

 

Thanks Ziggster.
Ill have to dress the sprockets up to make them look period but itll be worth it.

 

I'm a bit late to comment but regarding the conversation on chain tension changing - this is all true but it shouldn't cause much worry. Virtually all chain driven motorcycles with swingarms suffer the same fate, and it's not an issue. Just make sure the chain is never too tight in it's travel. If this was an issue, bikes would have swingarm pivots that were concentric with the countershaft sprocket. That's been tried but never caught on, even at the highest level of racing with 200+ hp bikes going over 200mph. Supercross is probably an even tougher application with the suspension travel they see.

 

I agree DesmoDog

I had enough time to get my gauge cluster bracket built tonight.

 

Just enough!!!

 

Hah, seems like a pretty optimistic speedometer for a fire truck, huh? Where does it drive from?

 

haha! I wouldn’t be surprised if that thing can do 100 mph if sprocket gearing is done right. One of my favourite vids of prewar cars. Mark Walker is a genius, and if you like the Darracq, check out his GN Thunderbug. One day, I’ve got to get to Goodwood to see these creations in person.

https://www.goodwood.com/grr/event-...0hp-land-speed-record-car-seriously-sideways/

 

It drives from the driver seat.

 

I love the 200hp Darraq Ziggster. It's my favorite car and an inspiration for this build.

 

I got my 3d printed front sprocket today! It looks like it's gonna work great!

 

No doubt your speedster will be capable of pegging the speedometer. What I was saying was 100 mph in a fire truck might be a little hard to achieve. Pretty sure I wouldn't want to be on board a 30's fire truck at a hundred either, haha.

 

You should fab up a chain guard that looks like it came from a period Schwinn bicycle. They were making bikes during this period.

 

My bad i misread your comment Fabber.

 

If anyone wants to figure out my engine rpms at different speeds thatd be awesome lol
The trans is a 38 American Lafrance with 3rd gear beaing a 1:1 ratio i think.
The Differential is 28 Pontiac. Ithink it's 3.88 ratio
The front sprocket is 27 tooth #100 chain and the rear is 33 tooth #100 chain.
Tires are 20"x6" lucas blackwalls. 32" od

 

Sounds like one of those math word problems from back when I was in school about 2 trains leaving Chicago at different times at different speeds and going in different directions and the question was "what color was the conductor's underwear" Or at least that's how some of the problems seemed. All kidding aside I'm sure someone will have an answer for you.

 

D'oh! I put them in the wrong order but the results should be the same.

EDIT: A different version of the same basic thing.

 

Looking good. Just a comment about your notch in the frame rail for the axle tube. Not sure what your plans are, but that could be a huge stress riser for cracks to start as it appears as though it is almost halfway through the frame rail.

 

Thanks DesmoDog. What front sprocket would I need to be around 2500 rpm at 60 mph?

You're correct Ziggster. Itll be plated inside and the differential mount plate acts asan upper plate as well.

 

I got the same results as you for your speed calcs. I think you would want to “overdrive” the two sprockets, meaning the one attached to the axle should have more teeth than that of the sprocket attached to the wheel. Just swapping the two sprockets will give you an “overall” gear ratio of 3.18. Speed is then as follows:

2000 rpm = 60 mph
2500 rpm = 75 mph
3000 rpm = 90 mph
3500 rpm = 105 mph

 

Also, with the gobs of torque that engine likely produces, you should no issues with “lowering” the gear ratio more. I remember my grandmother’s 64 Chrysler Saratoga had a diff ratio of 2.73 and with it’s 383 cu in engine could cruise effortlessly at 100 mph. Haha!

 

I can go no smaller than 33 teeth in the rear

 

You can up the tooth count on the front sprocket to get the lower ratio Ziggster was talking about.

 

A chain gaurd might be justified, but to compare this to a Schwinn would be like comparing boulders to pebbles. Lolol

 

If you can manage 40 teeth on tbe driving sprocket and keep the 33 teeth on the driven sprocket you can achieve the 3.18 overall gear ratio.

 

With all that torque and a relatively light car, you may not need 2500 at 60. 2000, or 2200 might be fine.

 

It's bad form to use the same size sprocket front and rear so here's what it would look like with a 32/33 combination.

 

I didn't see how you are adjusting chain tension? If the distance is relatively fixed between the two sprockets, you are limited to the combinations you can use based on chain pitch and sprocket diameters. There are ways to figure that out too but it's not a five minute spreadsheet. I may already have one that could be modded to work here though...

 

I would agree that you would be better served having a "taller" ratio.
1. This torque to weight beast won't need deeper gearing.
2. The engine likely isn't going to be happy at high RPMs.
This indicates an RPM limit of 3200. PDF warning http://www.thev12shop.com/downloads/ModelJV-12EngineData.pdf
3. Building the exhaust and cooling system will be easier when they aren't handling the temps of 'double taching' the engine and drivetrain (3K RPM at 60 MPH).
Jay Leno's '41 appears to be doing even more than that (2.5K RPM at 40 MPH), but it's got a LOT more weight. at 4:17 minute mark in the video.
4. I don't know the RPM limitations of that big chain drive, but it is typical to expect exponential increases in drivetrain stress. This is one of those questions to ask of the chain/sprocket vendors.