Author Topic: Two Cylinder Engine  (Read 13504 times)

Offline Roger B

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Re: Two Cylinder Engine
« Reply #135 on: January 19, 2019, 07:52:25 AM »
Back on this one. After some thought and a lot of checking I made up a spreadsheet for the cam profiles and set up to cut the lobes. This is one of the disadvantages of having a single machine, once there is a set up in place I can't do anything else until that set up is finished. Each lobe requires 60 cuts (6° steps) and each cut requires at least 30 turns of the cross slide handle  ::)
The cam followers are made from 6 mm silver steel drilled 5mm dia. 10mm deep. The camshaft and followers were cleaned up with a fine file and then fine abrasive cloth. They were all hardened, luckily without noticeable distortion, and now need a final polish.
Best regards

Roger

Online Kim

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Re: Two Cylinder Engine
« Reply #136 on: January 19, 2019, 05:44:37 PM »
Very nice looking cams, Roger.  That is a LOT of twiddling there.  I'll bet you're glad to have that behind you!
Kim

Offline Craig DeShong

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Re: Two Cylinder Engine
« Reply #137 on: January 21, 2019, 12:51:41 AM »
Lots of exacting work Roger.  Looks great!
Craig

Offline Art K

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Re: Two Cylinder Engine
« Reply #138 on: January 21, 2019, 01:12:42 AM »
Roger,
Good work on the cam, I must admit I have never made a hardened cam. I have made a few cams that way using cam-calc works great.
Art
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Online steamer

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Re: Two Cylinder Engine
« Reply #139 on: January 21, 2019, 01:19:07 AM »
Rodger    what material are you using for the cam?
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Offline Roger B

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Re: Two Cylinder Engine
« Reply #140 on: January 21, 2019, 12:21:26 PM »
Thank you all  :ThumbsUp:

Dave, the cam is made from 10mm diameter silver steel (drill rod).
Best regards

Roger

Offline fumopuc

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Re: Two Cylinder Engine
« Reply #141 on: January 21, 2019, 08:24:22 PM »
Hi Roger, nice job on the cam shaft.
Kind Regards
Achim

Offline AlexS

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Re: Two Cylinder Engine
« Reply #142 on: January 23, 2019, 09:59:09 PM »
Great job with cam and hardening. What are the specs of the cam, duration opening closing angles?

Offline michelko

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Re: Two Cylinder Engine
« Reply #143 on: January 24, 2019, 09:07:40 AM »
Hi nice work, can you give some more Information About the calculation of the cuts?

Michael

Offline gbritnell

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Re: Two Cylinder Engine
« Reply #144 on: January 24, 2019, 12:45:20 PM »
Roger,
I make all my cams like that with very good success. The difference is I use a rotary table on the mill.
gbritnell
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Offline b.lindsey

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Re: Two Cylinder Engine
« Reply #145 on: January 24, 2019, 02:05:50 PM »
Seems I have missed a few days of progress Roger. That cam came out very nicely!!

Bill

Offline Roger B

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Re: Two Cylinder Engine
« Reply #146 on: January 24, 2019, 03:24:02 PM »
Thank you all  :ThumbsUp:

This cam design is copied from my 3cc vertical engine. It is the forth version I made for that engine, I haven’t gone back to try the previous 3 again to see how they work with the engine in it’s final form.

The designs were made using the cam calculation programme on the MEN website:
http://modelenginenews.org/
Go to the menu on the left and open up ‘Resources’ and then ‘Design Centre’. This is a Java programme so I don’t know how well it will work on modern browsers.

One of our members has produced a version based on Excel which has a similar interface but I have not used it.

The design was based on values given in various books on model petrol engines.

Valve lift is 1.5mm (based on ¼ of the valve diameter)

Theoretical opening period is 260°

The angle between the lobes is 114°

This gives a theoretical overlap of 32°

The output of the programme is a table of angles and lifts for one lobe. I put this in a spreadsheet and shift the angles by the angle between lobes and also invert the lift values due to the way my milling fixture is set up.

This design programme does not allow for any clearances so I have reduced the base circle by 0.1mm. The transition was worked out by plotting each cut in a cad package and extrapolating.

I have attached the spreadsheet I used as well as the base circle drawing. The green circle is the base circle used in the calculation. The next black circle is reduced by 0.1mm. The ‘cuts’ for half a lobe are shown, the red line being the last from the cam design. The blue lines are then another three cuts to reach the reduced base circle.

George, I made this fixture before I had a rotary table and have kept using it. I can see benefits in a RT especially when cutting the base circle  :)
« Last Edit: January 24, 2019, 05:31:05 PM by Roger B »
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #147 on: January 24, 2019, 08:20:23 PM »
I am now moving onto assembly which is where I have to make all the little bits, studs, etc. First up was a thrust washer for the end of the camshaft. This was made using a spring collet so I could reverse it to face to other side. Next was the fixings for the timing gear cover, A few holes and some studs.
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #148 on: January 24, 2019, 08:27:22 PM »
The water pump body needed finishing as the distributor is mounted on the end of it. There was a hole that was no longer needed due to a design change that was filled with a piece of 3mm aluminium Loctited in place. One of the fastenings is a little bit special as it is also the clamping screw for the timing adjustment. Finally I needed to shorten the oilite  bush for the waterpump to give space for the water seal. As these are quite soft it was held in a spring collet and supported with a piece of 6mm silver steel held in the tailstock chuck.
Best regards

Roger

Offline Ye-Ole Steam Dude

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Re: Two Cylinder Engine
« Reply #149 on: January 24, 2019, 10:29:32 PM »
Hello Roger,

Looking good as it is coming together :ThumbsUp:

Have a great day,
Thomas