Author Topic: Hoglet help  (Read 3412 times)

Offline ozzie46

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Hoglet help
« on: March 10, 2014, 10:01:54 PM »
I have been pouring over all the reference material I can find on making cams, both in print and web based. I can't seem to be able to determine how to make the hoglet cams. I want to make them on the lathe as I don't have a good boring head for my mill.

   The cam blank is .465 with a base circle radius of .168.
 with a cam lift of .065.
   I think I have figured out the off set for turning the cam as .232 offset.
 
     I can't seem to figure out the opening and closing duration for the lobes.  I think that is what I need.

  I have read Steve Hucks "Offset turning the cam shaft"
 tutorial till I'm blue in the face and I still don't know what to do.
  But his tutorial isn't really about how to draw the profile but how to machine it once you have the profile. How to machine it I understand.

  The 3 lobes are located around the shaft thus:  1 lobe at "0"
 degrees,   1 lobe at "101" degrees counterclockwise from "0"
and 1 at "113" degrees from "0" clockwise.
Thanks in advance.
 

 Ron
« Last Edit: March 11, 2014, 01:07:13 PM by ozzie46 »

Offline pgp001

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Re: Hoglet help
« Reply #1 on: March 10, 2014, 10:52:20 PM »
Another of our members on here "Graham Meek" has written a very good article on making cams.
I followed this procedure for my own IC engine and I have to say it was very good.
I hope this link to another website does not break any rules.

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

Phil

Offline ozzie46

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Re: Hoglet help
« Reply #2 on: March 11, 2014, 12:17:29 AM »
  Thanks for the link. That is a very good read.
 
 I made cams for my "mastiff"engine using L.C. Masons instructions,which were very complete, but he had the opening and closing angles for the cams in the instructions.

  The "Hoglet" plans don't show any opening and closing angles for the cams and that is what I need.

  Ron

Offline Camm-1

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Re: Hoglet help
« Reply #3 on: March 11, 2014, 05:30:37 AM »
Hi Ron
Then I built my Hoglet I had the same problem and get these instructions from Clarence Elias
that helped me
Ove

Timing the cam gear to the cam shaft
 
This is not critical, but it's good to get it as close a possible. Refer to drawing 5 of 12. In the upper right corner is a detail - Cam Gear-Camshaft orientation drawing. Get as close as you can to that layout.
 
Timing the cam to the crank
1. Have you made a mark on the flywheel to measure when the front piston is Top Dead Center? If not, now would be a good time. Rotate the crank so the front piston is TDC. You can find TDC by sticking a dial indicator through the spark-plug hole. Make a calibration mark on the flywheel. Now rotate the crank 90 degrees (Clockwise when viewed from the cam side) - it is now half way through the stroke. This is where the valve should be wide open.
 
2. Make sure the tapered screw that locks the gear on the crank is loose. Put a dial indicator on the front intake valve lifter. Now, by spinning the gear on the crank, find the highest point of lift. Lock the gear on the crank. Done!
 
Timing the Ignition
Rotate the engine so the front piston is at TDC at the start of the power stroke. Now move the timing lever till you get a spark. The engine will now fire TDC which will cause the engine to run. Once it is running you can fine-tune the spark timing to give the best performance.

Offline mikemill

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Re: Hoglet help
« Reply #4 on: March 11, 2014, 09:54:56 AM »
I think more has been written on the subject of making cams than any other aspect of model engineering, those with CNC may have encountered the hours of blogs by a professional racing cam maker in the US on the CNC Zone site. Making individual cams and then keying them on a shaft at the correct angle is a very effective way of cutting the profile accurately. Then it occurred to me why not cut the profile with CNC where you have complete control of the shape as you draw it first, also accurately cut the slot for the key at the same time.
What do others think, is this a feasible way of making cams?

Mike
« Last Edit: March 11, 2014, 11:41:40 AM by mikemill »

Offline RickBarnes

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Re: Hoglet help
« Reply #5 on: March 11, 2014, 11:15:43 AM »
I think making cams is a great reason to improve the overhead rotary valve. 

Offline gbritnell

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Re: Hoglet help
« Reply #6 on: March 11, 2014, 12:31:38 PM »
Hi Mike,

 In response to your reply, I think you're correct on the amount of information that has been written about cams and cam making.
 
 I think it can be broken down into several categories, the first one would be what type of machinery a person would have for making a cam. If just a lathe an a mill without the benefit of a rotary table or dividing head then making the lobes separately would certainly be high on the list although Steve Huck's method would be one to consider. Added to this would be the amount of cylinders/lobes that the cam needs. For just a couple of cylinders timing the lobes shouldn't be that big of a problem, but in engines having 4, 6 or more cylinders I personally don't think this is the best way to go.

 Another condition would be if the builder wanted the cam hardened. This would also required the separate lobe method or having a purpose built grinder to finish the cam once hardened.

 In my modeling career I have used all but the hardened and ground method, not wanting to go to the trouble of building a grinder for one or two cams now and then. I have settled on the step-off method utilizing a horizontal/vertical rotary table with tailstock. For those who have followed my builds they will be acquainted with this method. Basically the cam features are developed and drawn in my CAD program and then a machining chart is made up to cut the lobes leaving small facets on the surface, but I must say that early on before I had a CAD program I used this same method but with hand drawn profiles.

 The last and latest method would certainly be the use of CNC equipment but that takes cam making into another area completely. I know more and more fellows are getting into CNC work but at this time I don't thing it's a viable option for most of us.

gbritnell
 

 

 
Talent unshared is talent wasted.

Offline ozzie46

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Re: Hoglet help
« Reply #7 on: March 11, 2014, 01:03:35 PM »
 
   Thanks Camm-1. That is info I needed for after the cam is made and installed. I was wondering about that last night.


  Thanks for input but no CNC here, only manual machines.

   George, I need to generate the profile and can't figure out how to arrive at the opening and closing angles for the cams to machine the cam form.

  I have tried to figure out the step off method,how you arrive at the dimensions for the cut, but it eludes me. I would love to be able to do it as I make all my parts out of solid stock. I some times get to thin put hole in the piece.

   All good information Thanks guys. 

  Now how to plot out cam profile for machining?   :thinking: :thinking: :thinking:

  Ron

Offline Jasonb

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Re: Hoglet help
« Reply #8 on: March 11, 2014, 01:45:58 PM »
Take a big sheet of paper or a CAD programe and draw out the base radius, lift with a small radiused tip and then swing the 0.4" flank radius to touch the two. You can then measure where the flank radius meets the base radius to get your angle. But to save you the trouble here it is. the two angled lines are 25deg above horizontal so you can work out your settings from there.

J

PS if you want to calculate the settings for milling then Marv's cam calculator is worth a go
http://www.myvirtualnetwork.com/mklotz/#shop

« Last Edit: March 11, 2014, 01:53:41 PM by Jasonb »

Offline ozzie46

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Re: Hoglet help
« Reply #9 on: March 11, 2014, 01:53:44 PM »


  Thanks Jason. Now to drawing board to practice how to do this.   :ThumbsUp: :ThumbsUp:

  Ron