Author Topic: vintage V twin  (Read 37872 times)

Offline OKTomT

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vintage V twin
« on: May 26, 2014, 07:10:34 PM »
I am starting a new engine build. its going to be a v twin this time.
This is going to be a scratch build just make it up as I go.
my goal is to make this engine better quality then the last one. lighter, more cc, more rpm,less oil leaks, and keep the vintage look.
Fill free to give advice about my construction ideas.
 I have started building the crankshaft. Here is a picture of it.


         

Offline Brass_Machine

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Re: vintage V twin
« Reply #1 on: May 26, 2014, 08:41:02 PM »
Awesome! I am going to watch this one with anticipation!

Eric
Science is fun.

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Offline vtsteam

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Re: vintage V twin
« Reply #2 on: May 26, 2014, 10:06:48 PM »
Oh boy, this is going to be good!  :coffee: :coffee: :coffee: :coffee: :coffee:
I love it when a Plan B comes together!
Steve
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Offline BronxFigs

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Re: vintage V twin
« Reply #3 on: May 28, 2014, 08:24:19 AM »
Tommy T-

Here we go again....only with two cylinders this time.  Great!  Can't wait for the rest.

Idea:  Use two scaled up, "Hoglet" cylinders for a 60 degree V-Twin.  Drawings for the "Hoglet"are easy to find. Or.....adapt a cylinder design from an air-cooled,  radial, aero engine.  If there is a crankcase  a large diameter steel tube for the crankcase, and weld on two pieces of steel channel-iron, or square steel tubing,  for the mounting flanges for the cylinders.  The sides of the tubing can be cut with the same radius as the crankcase for a close fit.  The channel iron/tube then can be welded to the crankcase at 60 or 90 degrees

So far this new build is starting off like your first engine.  I see tapered roller bearings, and cut outs for balancing, in the two flywheels.

Because your engine builds are so informative, please note all the design changes that will use to make this engine lighter, a better quality, have less oil leaks, etc.  To the experienced builders these changes might be obvious, but to me, with so little experience, it helps if changes are explained, and noted.   It would be great if you can mention the dimensions of the major parts e.g. con-rod length, bore, stroke, etc.

Looking forward to seeing your progress.


Frank
« Last Edit: May 28, 2014, 08:52:59 AM by BronxFigs »

Offline Kjelle

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Re: vintage V twin
« Reply #4 on: May 28, 2014, 01:44:51 PM »
Ok, popcorn and soda in their places, Check
Comfy chair in front of the computer, Check...

BRING IT ON!

Kjelle :D

Offline BronxFigs

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Re: vintage V twin
« Reply #5 on: May 28, 2014, 05:57:30 PM »
Tom-

Already some questions....

What material(s) did you use to fabricate the crankshaft/flywheel combination, and also the crank pin?  Diameter of the flywheels?


Frank

Offline John Stevenson

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Re: vintage V twin
« Reply #6 on: May 28, 2014, 06:02:24 PM »
Awesome, can't wait.

The last one was a classic, in fact best post on this forum for the whole year.
John Stevenson

Offline micktoon

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Re: vintage V twin
« Reply #7 on: May 28, 2014, 06:37:56 PM »
I am looking forward to this too Tom, enjoyed every post last time , so good luck and keep up the good work  :thumbup:

 Cheers Mick

Offline Manxmodder

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Re: vintage V twin
« Reply #8 on: May 28, 2014, 09:30:49 PM »
 Hi Tom,as the others have said this project will be worth following.

I see you're using taper rollers for the main bearings. You may experience some problems with brinelling and surface fatigue due to the slight flex of the crankshaft when it is running.

Taper rollers do not tolerate bending loads which load the outer edges of the roller elements and outer race.

My own preference would be barrel roller bearings or spherical roller bearings as these are designed with shaft flexure type of stresses in mind. Even the humble ball bearing has better resistance to the type of loadings seen on a crankshaft than the tapers do.

Just my thoughts and views on the matter of suitable main bearings.....OZ.

Helixes aren't always downward spirals,sometimes they're screwed up

Offline OKTomT

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Re: vintage V twin
« Reply #9 on: May 28, 2014, 10:08:37 PM »
thanks for the support guys.
Here are the specs.
Flywheels 1.250 x 8"
Crank pin 1"  3* taper
Rod pin 1"  3* taper on  one end press fit on the other
bore 3.275 x 2
stroke 3.75
1036 cc  :thumbup:
This build is going to take a little longer than the last. I am going to try to make the best parts that I can with these worn out machines before I move on to the next part.
The crank has a tir .030 because of the rod pin and I need to figure out where I am off and get it right before I move on. The crank in the last engine had a tir of .008 and  the rod pin was tapered on both ends. so I know I can get this one a  lot closer. I will keep you all  posted as I make progress.
Manxmodder  thanks for pointing this out before I  built the crank cases I think you are right.  I am going to change to roller bearings  Tom

Offline Joe in Oz

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Re: vintage V twin
« Reply #10 on: May 29, 2014, 03:31:18 AM »
I strongly agree with Manxmodder: taper rollers are wrong for this application. Best would be barrel rollers on the drive side (or both), deep groove on the non-drive side....
Taper roller bearings need to be preloaded to meet their design parameters - and you can't do that with a crankshaft since you introduce bending forces on the crankpin if you did.
Cheers and enthusiastically anticipating the build log!
Joe

Offline John Stevenson

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Re: vintage V twin
« Reply #11 on: May 29, 2014, 05:03:38 AM »
Sorry but I disagree about the taper rollers.
In theory what you say *may* be correct but Velocette's used taper rollers all thru the production life of their later series of machines with no problems.
You assembled the engine cold with an 8 thou gap between the crankcases so that was the preload
John Stevenson

Offline billmac

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Re: vintage V twin
« Reply #12 on: May 29, 2014, 07:22:04 AM »
Just to add to what John has said about Velocette bottom ends. The design resulted in a rather narrow bottom end which raises its stiffness significantly. This is a big advantage in a high performance single (or even more so a V twin) , because it reduces the deflection in the mainshafts and crankpin and tends to produce a smoother running engine. In the case of the Velocette it also allowed the unusual arrangement of the clutch and final drive sprocket, which are quite different to any other similar machine. I seem to recall that Joe Craig of Norton fame believed that the Velocette bottom end was a better design than his Manx Nortons, although he didn't have the same high opinion of the rest of the engine. I can't find a quote for that so maybe my memory is faulty, but in any case I think the OPs design is interesting and if the crankcase is made strong enough will result in a great engine.

Offline vtsteam

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Re: vintage V twin
« Reply #13 on: May 29, 2014, 09:16:46 AM »
Already a great read! Learning a lot.
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline OKTomT

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Re: vintage V twin
« Reply #14 on: May 29, 2014, 10:37:33 PM »
Thanks for all the input. I do appreciate you taking the time to post your opinion.

Frank the flywheels are 1018 and the pins 1045 ground and polished. this will work for me but I am sure there is a better material.
 
Getting the crankshaft to run true is quite a challenge for me. I would like to know how you would contain the rod pin and how you would machine the fit in the flywheels. The main pins are tapered at 3* and run true with the fly wheels but rod pin is off by .030 tir.  I  bored and cut the taper for the main pins in the lathe then put the flywheels in the mill and bored the rod pin fit. One of them was bored for a press fit and the other was left under size and put back in the lathe and the taper cut. I think there must be a better way.  On the last engine I put a 3 jaw self centering chuck in my 4 jaw chuck and set it off center to bore and taper the rod pin holes but the finish was bad due to the slow speed I had to use.  Thanks Tom

Offline Manxmodder

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Re: vintage V twin
« Reply #15 on: May 29, 2014, 11:20:21 PM »
Hi Tom, I have made flywheels for 2 stroke cranks in the past(about 4.75 inches dia) and my method was to bolt the 2 flywheels together and machine the crankpin holes right through as one.

I have also seen other guys tack weld the flywheels together and then separate them after all the main pin and crankpin boring was completeed . These methods guarantee alignment of the pin bores.....OZ.
Helixes aren't always downward spirals,sometimes they're screwed up

Offline billmac

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Re: vintage V twin
« Reply #16 on: May 30, 2014, 07:16:26 AM »
Hi Tom.

A TIR of .030" for the crank pin is way too much unfortunately (as I am sure you appreciate) regardless of the type of bearing you intend to use. The suggestion to bore the flywheels together should help, but you obviously can't do the taper turning right through that way. A tapered fit crank pin is traditional, but not all engines were made like that. Some had parallel pins and were a press fit in both flywheels. This makes lining up the flywheels to get the mainshafts running concentric more of a challenge of course. With a taper fit you can pull them up on the nuts lightly then 'bump' the flywheels on a big lump of wood or a chunk of brass or lead until you get them true, then pull them up tight. It is best to use lathe centres (or bench centres) to test for this alignment.

Just a thought that might give you a way forward - Villiers engines used a parallel fit crank pin that was a light press fit. This allowed for alignment adjustment. The crankpin was bored at each end and after alignment you pressed in a plug in each end, a good press fit. This caused the ends of the crankpin to expand minutely and increase the strength of the overall fit in the flywheels. The Villiers design perhaps was not the best, but they made them in the tens of thousands so might be worth investigating this method, since it would allow you to bore out your flywheels together and in one setting, which should give you much better alignment. You might be able to rescue your existing flywheels this way, but you would obviously need a new crankpin.

Watching progress with interest.

Offline tom osselton

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Re: vintage V twin
« Reply #17 on: May 30, 2014, 03:35:34 PM »
So I'm scratching my head what does "tir" stand for?

Offline Bluechip

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Re: vintage V twin
« Reply #18 on: May 30, 2014, 03:38:30 PM »
Total Included / Indicated Runout or similar ...  :thumbup:

Dave
I have a few modest talents. Knowing what I'm doing isn't one of them.

Offline tom osselton

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Re: vintage V twin
« Reply #19 on: May 30, 2014, 03:48:50 PM »
Ok thanks, I was just wondering I'm going to have to make one of these soon for a twin.

Offline billmac

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Re: vintage V twin
« Reply #20 on: May 30, 2014, 03:50:54 PM »
TIR stands for Total Indicator Reading. If you set up an indicator so that it bears on a shaft, then rotate the shaft, the TIR is the difference between the lowest and highest readings on the dial.  Or you can find the minimum, set the dial to zero, then the TIR will be the maximum reading that you get on the dial.


Offline John Stevenson

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Re: vintage V twin
« Reply #21 on: May 30, 2014, 05:43:30 PM »
Just my take on it when making flywheels with tapered crank pins is to make one side and finish both bores and skim the outside to be true.
Leave the other side oversize but machined up all round.

Then mark out and bore the other tapered hole for the pin, machine the mainshaft hole to about 3/4 finished size

Make a dummy crank pin with just two tapers on it and virtually no parallel part, you need to be between centres to do this accurately. The idea is to get both halves to clamp together tight but with no gap.

Then holding the whole assembly on the good mainshaft and clock the good flywheel side you can then  bore the other mainshaft hole to finished size.

That should get everything running true.
John Stevenson

Offline billmac

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Re: vintage V twin
« Reply #22 on: May 30, 2014, 06:32:40 PM »
John -

Took me a few minutes to understand what you are saying, but I really like that method. Will file that away for later.

Offline AussieJimG

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Re: vintage V twin
« Reply #23 on: May 31, 2014, 06:08:58 AM »
Following this one with interest

Jim

Offline OKTomT

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Re: vintage V twin
« Reply #24 on: May 31, 2014, 10:42:33 AM »
Thanks guys
I had thought of boring the crank pin holes straight through with the fly wheels welded together and drill a hole in the ends of the crank pin for a tapered pipe plug to expand the pin for a tight fit. but I chose to go with proven method thinking that the plugs would not hold the pin tight. Press in plugs sound like a good idea but may be hard to remove.

John your way sounds good but making a pin with two tapers that seat In there tapered holes and the face of the flywheels meet up at the same time in beyond my skills. but what I could do is leave one of the rod pin ends a press fit that way I could just press them together after I tighten up the taper end. I am going to do some checking and see where I am off then make a plan to repair.   Tom