Author Topic: Cam Jig Help  (Read 2945 times)

Offline ozzie46

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Cam Jig Help
« on: November 26, 2013, 04:50:26 PM »
  I am trying to make a cam assmbly jig for assembling a multi piece cam as L.C. Mason designed for his Mastiff engine. I have attached a pdf of the jig assemby.

 I can't use his total design as the Mastiff is an opposed “Boxer” style engine and the engine I want to build is an in-line 4 cyl., ETWs Sealion.

  I want to use the Mastiff type jig so I can harden the lobes before being installed on the cam shaft and skip any possible warping of the cam shaft during the hardening process. I also attached a pdf of the Sealion Cam machining notes as well as a pdf of my attempt at figuring out the angular position of the center points of the cam lobes.
   

  The notes say that the Sealion cam rotates clockwise from the timing end.
 
  Would some one be so kind as to review my work and see if it is correct and let me know what to do if it isn't?

  The process of making the cam for the “mastiff engine ,I feel, was very easy and I believe others could use it as well. 

  Thanks in advance
 Ron

Offline stevehuckss396

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Re: Cam Jig Help
« Reply #1 on: November 26, 2013, 09:44:26 PM »
I'm off to work on something but I can look at it later tonight if you can wait.
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline gbritnell

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Re: Cam Jig Help
« Reply #2 on: November 26, 2013, 11:52:46 PM »
Hi Ron,
For an inline 4 cylinder engine the firing order is 1-3-4-2. This is with a flat plane crank. (1 & 4 up and 2 & 3 down) If you start with the exhaust lobes for each cylinder they would be, starting with #1 cylinder, 90 degrees behind each other, meaning with #1 cylinder at TDC #3 cylinder would be 90 degrees behind and so forth and so on. I started with the exhaust lobe because with the lobe separation angle the exhaust opens first then the intake. Lets say #1 cylinder exhaust lobe is at it's peak lift (TDC so to speak) The intake lobe could be anywhere from 95 to 115 degrees behind depending on the cam specs., so each of the other cylinders would have the same lobe positioning relative to the exhaust lobe.  The lobe separation angles for the Mastiff are 110 degrees so therefore here is the proper spacing for the lobes. Using #1 exhaust lobe as the starting -0- point at it's peak.
 
#1 exh. TDC                 #1 int. 110 degrees behind                                                           #1 exh. TDC                 #1 int. 110 degrees behind
#3 exh. 90 behind       #3 int. 200 degrees behind    FIRING ORDER                                 #2 exh. 270 behind      #2 int. 20 degrees behind.      ENGINE POSITION
#4 exh. 180 behind      #4 int. 290 degrees behind                                                          #3 exh. 90 behind       #3 int. 200 degrees behind
#2 exh. 270 behind      #2 int. 20 degrees behind.                                                           #4 exh. 180 behind      #4 int. 290 degrees behind                                                           

I hope this helps.
gbritnell
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Offline ozzie46

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Re: Cam Jig Help
« Reply #3 on: November 27, 2013, 01:02:49 AM »
   Thanks George . I'm planning this for the Sealion and ETWs' build notes say the firing order is 1243 with the camshaft rotating clockwise from the timing gear end. It does have a flat plane crank.
    So I guess my little Cam jig circle is right ?

  Steve , When ever you can Thanks.

 Ron

  Edit  It looks like I forgot to label # 4 intake line at 290 degrees
« Last Edit: November 27, 2013, 01:06:19 AM by ozzie46 »

Offline stevehuckss396

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Re: Cam Jig Help
« Reply #4 on: November 27, 2013, 01:15:37 AM »
I think you have it backward ozzie. Your exhaust lobes look good but the intake should lag the exhaust. On your template it appears that your intake lobes will lead the exhaust lobes by 110 degrees. What you have on the template would work for a CCW rotation.
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline ozzie46

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Re: Cam Jig Help
« Reply #5 on: November 27, 2013, 01:44:22 AM »


  Thanks Steve, will change it around.

  Ron

Offline ozzie46

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Re: Cam Jig Help
« Reply #6 on: November 27, 2013, 02:58:57 PM »
  Steve, here is a revised cam lobe circle drawing, is it right?

  Ron

Offline stevehuckss396

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Re: Cam Jig Help
« Reply #7 on: November 27, 2013, 11:52:30 PM »
That looks like a good cam for a CW rotation assuming the In 2 at 250 degrees and it's really In 1. Im sure it is a typo.

If the crankshaft directly drives the cam you need the first one you posted. If the crank and cam are coupled with an idler gear, belt or chain you need this one.
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Offline stevehuckss396

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Re: Cam Jig Help
« Reply #8 on: November 27, 2013, 11:56:41 PM »
Just curious Oz, why are you hardening the parts. If you machine some O1 drill rod it will last a lifetime with proper oil. Machining all in one piece will place the lobes exactly where they need to be. That will be very hard to do one lobe at a time.

Hope all goes well for you I look forward to seeing it running!!
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline ozzie46

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Re: Cam Jig Help
« Reply #9 on: November 28, 2013, 01:21:22 AM »



  Thanks Steve. Yes the I 2 at 250 is a typo. It is supposed to be I 1 at 250 degrees.

  As far as hardening the parts, that's the way L.C. Mason said to do it for the "Mastiff".
 The Mastiff cam is made this way and seemed like a good way to make a cam. I had no trouble at all in lining up the lobes. Once the loctite sets up it's just like a one piece cam.

 I don't know anything about metals other than what is called out for in the plans and build notes. The Mastiff was my 3rd engine if you count my paddleducks marine engine and my Simplex loco chassis and my one and only IC engine so far. So I am pretty much obliged to follow the plans pretty close.

  I do deviate when it comes to castings as I don't use them. I try to carve the parts out of solid manually. That's what I'm doing with the Sealion. I am building up a block for the Sealion from 5 pieces of aluminum that will be screwed  and J B welded together.

  Ron

Offline pgp001

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Re: Cam Jig Help
« Reply #10 on: November 29, 2013, 11:15:15 PM »
You could do a lot worse than reading Graham Meek's article on making cams.
There is some very useful info in it, I used those principles to make the cams on my Bonds Simplex engine.

http://modelenginenews.org/techniques/meek_cams.html

Phil

Offline ozzie46

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Re: Cam Jig Help
« Reply #11 on: November 30, 2013, 02:08:12 AM »


  Thanks Phil, I will study that for sure.

 Ron