Author Topic: The "2-Bits" V-Twin  (Read 10530 times)

Offline RReid

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The "2-Bits" V-Twin
« on: February 28, 2022, 01:27:22 AM »
Introducing the “2-Bits” 50 degree V-twin engine.

I've been working on the plans for this project in the background all through the Stirling Fan build and even before. It is inspired by; based on; but not a scale model of the engines developed by Glenn H. Curtiss for use in his successful line of early motorcycles. The V-twin was introduced as an option to the “standard” single starting in 1903, and continuing until mid 1913 when the the motorcycle factory assets were offered for sale. Mr. Curtiss was turning his attention completely to aviation, an interest sparked in 1904 when he began to supply V-twins to Captain Thomas Scott Baldwin to power the dirigible he was developing that was soon capable of sustained and controlled flight even before the Wright Bros. first powered flight.







For anyone interested, a good and much more detailed history of these early years may be found here:
https://curtissmotorcycles.com/history/

As I said, my version is not intended as an accurate scale model. It does, however, include the most distinctive features of the Curtiss engines.
> 50 degree V-twin cylinder layout
> Atmospheric intake valve
> Intake-over-Exhaust valve arrangement.
> Exhaust cams mounted low and centered, just above the crank axis. Each valve is driven by pushrods acting through a pair of rockers on a low mounted shaft external to the crankcase.




For those who may not be familiar with the term, "2-bits" is an American colloquialism for a quarter of a dollar, or 25 cents. This engine has two "bits" in the form of cylinders, and is 1/4 of a V8! I plan to install a 25 cent piece on the finished engine in lieu of a builders plate.

Bore and stroke of the engine are 0.75" x 1" (19mm x 25.2mm). This is the same as the Upshur engine I finished recently, and a size that worked out well with my equipment,


« Last Edit: March 08, 2022, 01:18:14 AM by RReid »
Regards,
Ron

Offline RReid

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Re: The "2-Bits" V-Twin
« Reply #1 on: February 28, 2022, 02:15:05 AM »
I commenced cutting metal for the crankcase this morning. My original intention had been to make the main body of the case from a piece of heavy wall brass tubing (3” OD, 0.25” wall), but at around $50 for a two inch piece of material I had second thoughts. The same size piece in aluminum would only be a few bucks and good second option, not least because the Curtiss engine did use an aluminum crankcase.

Then I considered those chunks of ali I brought home from Tx that have been a source of material for a few parts in other projects already. The larger one is 1.5” thick, which is just what I need. That's the “Pac-Man” in the first image below. And I have an almost unused (therefore sharp, hopefully) 2.125” OD x 1.75” deep hole saw. If I can get all the way through with that, then there will just a relatively small amount left to bore.

So I got to work cutting out a blank on the bandsaw. That poor thing must have been thinking “this isn't in my contract”, but it got the job done.






Then I mounted it in the 4-jaw to start turning one end to near size.

Regards,
Ron

Offline propforward

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Re: The "2-Bits" V-Twin
« Reply #2 on: February 28, 2022, 02:32:15 AM »
This looks like a great build! I’ll be following along.
Stuart

Forging ahead regardless.

Offline Art K

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Re: The "2-Bits" V-Twin
« Reply #3 on: February 28, 2022, 02:47:49 AM »
Ron,
For our anniversary in Oct. 2018 we visited to the National Motorcycle Museum in Anamosa, Iowa. This was on display. It is a 1906 Curtis.

I personally am partial to the 27 Brough Superior but have no idea how to find enough info to build one, even if I didn't have 3 or so engines on the list to work on first.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Hugh Currin

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Re: The "2-Bits" V-Twin
« Reply #4 on: February 28, 2022, 03:53:06 PM »
Ron:

I've always loved these first gen motorcycle engines. Will be fun to follow along.

I don't understand the valving, but sure it'll become apparent as the build progresses.

Thanks.
Hugh

Offline Roger B

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Re: The "2-Bits" V-Twin
« Reply #5 on: February 28, 2022, 04:55:50 PM »
An interesting project to follow  :ThumbsUp:  :ThumbsUp:  :wine1:

I do like the old engines and how they solved the various problems  :) I guess that with a 50° engine there must be two separate exhaust cams on the camshaft  :headscratch:
Best regards

Roger

Offline RReid

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Re: The "2-Bits" V-Twin
« Reply #6 on: February 28, 2022, 07:52:01 PM »
Thanks Stuart. Thanks for taking an interest guys!

Art - Apparently that rear seat w/ handlebars the bike in your photo from the museum has was an extra cost option!

Hugh - I've put in a couple of drawings below with some of the other parts hidden or made wireframe, so as to shown the valves, cams, and rocker arrangement more clearly. For the front cylinder I've colored the intake valve green, the exhaust valve red. The intake is an atmospheric valve (pulled open by low pressure in the cylinder on the intake stroke), so is not driven from a cam.

Roger - That's correct, there is a cam for each exhaust valve. The lobes are just arbitrarily set at 90 degrees apart on the drawing.




Regards,
Ron

Offline Hugh Currin

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Re: The "2-Bits" V-Twin
« Reply #7 on: March 01, 2022, 12:04:39 AM »
Ah Ha, there is a cam.

Thanks.
Hugh

Offline kuhncw

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Re: The "2-Bits" V-Twin
« Reply #8 on: March 01, 2022, 03:21:54 AM »
Very interesting project.  Which CAD system are you using?

If anyone happens to visit Hammondsport, NY,  the Glen Curtiss Museum is well worth seeing.

https://glennhcurtissmuseum.org/exhibits-on-display/


Chuck

Offline RReid

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Re: The "2-Bits" V-Twin
« Reply #9 on: March 01, 2022, 02:58:42 PM »
Hi Chuck. I'm using Alibre Atom 3D.

That would be a fun museum to visit. When I lived and worked in Maryland I went up to Watkins Glen a few times to help the race team my son worked for. One time on a free day we went over to Ithaca and rented kayaks; if we'd known about it the museum would have been just as fun and just as close the opposite direction! From California though it's a bit of a hike.
Regards,
Ron

Online crueby

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Re: The "2-Bits" V-Twin
« Reply #10 on: March 01, 2022, 03:20:07 PM »
That Curtiss museum is a great place. The bikes that really got my attention were the ones where he put a rotary engine inside the rear wheel to power them. Must have been an interesting ride, with that much wieght spinning with the wheel. Not sure if they are always on display there, last time I was there they had them in the front lobby.

Offline sid pileski

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Re: The "2-Bits" V-Twin
« Reply #11 on: March 01, 2022, 04:52:55 PM »
Chris- I've been to the museum a couple of times.
I don't think Curtiss did the engine in the wheel thing.
Can't recall who was the mfg. on that......

Sid

Online crueby

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Re: The "2-Bits" V-Twin
« Reply #12 on: March 01, 2022, 05:05:32 PM »
Chris- I've been to the museum a couple of times.
I don't think Curtiss did the engine in the wheel thing.
Can't recall who was the mfg. on that......

Sid
There was the Megola bikes, but that had the rotary engine in the front wheel, the ones Curtiss museum had on display were in the rear wheel. Verdel made some with a radial engine in the frame. I thought the ones displayed were an experiment that Curtiss did, never produced commercially, but I could be wrong.

Offline RReid

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Re: The "2-Bits" V-Twin
« Reply #13 on: March 02, 2022, 12:56:15 AM »
In the last installment, I was turning the OD of the crankcase blank. To finish that I had to turn it around so as to turn off the bit that had been in the chuck jaws.


Then it was time to find out if a run of the mill hardware store hole saw, and my tired old drill press, would be up to the task of chewing through 1.5” of aluminum. Here we are about ˝ way through. So far so good.


And the answer is yes, it will work. Not quickly, not quickly at all, but it got there. I might have gone faster, but I couldn't bear down too hard without slipping the belts on the drill press. That's fine though, given that the clamping arrangement was a little marginal. Better the belts slip than the part!


Then it was back onto the lathe to bring the ID to size. Again I would have to turn it around to finish the last little bit because it was up against the jaws. You can see that bit in this image.


And done. Easier than buying a piece of heavy wall tubing? Heck no! Worth it? I don't regret doing it the hard way this time and I'm happy with the result, so sure. I just hope I don't mess up and have to do it again!

Regards,
Ron

Online Kim

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Re: The "2-Bits" V-Twin
« Reply #14 on: March 02, 2022, 03:56:13 PM »
Very nice length of pipe you made there, Ron!  And you have the core to use in some future project to boot!   :popcorn: :popcorn:
Kim