# Machining 1/4 Scale V8 Engine Cam?



## QSPSB (Dec 1, 2010)

Hey guys... Long time viewer... first time question..

I"m planing on machining a 1/4 scale blown v8 engine within a few months and have a question regarding the cam grinding... I'm building a custom rotary table type cam grinder with a fixed grinder and need to know what type of 4th axis cam program you would suggest i use... I'm doing the majority of my CAD work in solid edge 2D... do you think solid edge 2D will work for this application? or perhaps another CAD program?

I want it to run much like this one... except I'll use the rotary table in place of the headstock..
[ame]http://www.youtube.com/user/QSPSB#p/u/47/o2d2cR3liE0[/ame]
[ame]http://www.youtube.com/user/QSPSB#p/u/46/UeM-IRJBq3I[/ame]

Thanks in advance


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## stevehuckss396 (Dec 1, 2010)

Are you dead set on building a cnc machine? 

You could save alot of money and time programing by turning the camshaft in a simple fixture in the lathe.

I would be interested in seeing how you go about producing the Gcode for a cam. Always wondered how that is done.


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## mu38&Bg# (Dec 1, 2010)

They wrote their own software for that setup. Any CAM software that can handle 4th axis continuous machining will write code for the cam. The trouble is designing the cam if you're doing something other than a simple harmonic cam. Software that does 4th axis continuous isn't cheap as well, or at least I haven't found anything under 4kUSD. While a 4th axis would normally be perpendicular to the spindle, this should be something the CAM supplier can sort for you. The 2D CAD software should be fine as you'll just bring the profile into the CAM to generate the code.

This is the original video.
[ame]http://www.youtube.com/watch?v=OIWyGtXEgR4[/ame]


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## QSPSB (Dec 2, 2010)

Thanks... Yes it's just a harmonic type cam... I've look in to quite a few 4th axis cam programs... looks like I'm going to need to spend a few grand for a decent one... I plan on machining quite a few different lift cams as well.. 
http://www.sprutcam.com/gallery.asp  looks like a good one!


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## mu38&Bg# (Dec 2, 2010)

For a simple 4 arc cam I'd write the Gcode by hand. It will take some trigonometry to find the centers of the arcs, but I'm sure I could do it in half a day. Probably another half a day to familiarize myself with tool radius compensation which I don't use right now. Depending on what your time is worth, it might be easier to buy the software.

I've been tossing around the idea of a 4 axis CAM for a long time. I use my machines to make money and still haven't justified spending that kind of cash. I don't get work that requires it, but I could always find projects for it. Sprut looks good, but again in the 4k+USD price range for SprutCam Master that would do what I want.


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## QSPSB (Dec 2, 2010)

Yeah i wish i had the time to sit down a learn a little more about writing up g codes... I've done some in the past and all went well... but nothing quite as complicating as a cam... I'm thinking about going with a 0.93 lift both intake/exhaust.. flat tappet design with a 180 degree spit between lobes with a 280 degree duration... how's these numbers sound to you... By the way this engine will be a 1/4 blown hemi... so i may need to increase the lift a tad... i want it to lope...

Thanks


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## stevehuckss396 (Dec 2, 2010)

QSPSB  said:
			
		

> Yeah i wish i had the time to sit down a learn a little more about writing up g codes... I've done some in the past and all went well... but nothing quite as complicating as a cam... I'm thinking about going with a 0.93 lift both intake/exhaust.. flat tappet design with a 180 degree spit between lobes with a 280 degree duration... how's these numbers sound to you... By the way this engine will be a 1/4 blown hemi... so i may need to increase the lift a tad... i want it to lope...
> 
> Thanks



You might want to go with 110 degree lobe centers and 280 minimum on the duration. I was thinking of going 300 or 310 on mine. The lift will be fine. The lope comes from cam timing and duration not lift.


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## QSPSB (Dec 2, 2010)

clearly my mistake... Lift/Duration/Overlap... no biggie it's all good

Hmm are you sure about the degree? I was told i could even go with an 278 degree duration with a 0.490/0.480 lift... Reason being.. It's a two lobe blower rotor...

Input wanted guys... I surely don't want to create the wrong G-Code for my engines cam shafts

Thanks


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## jpeter (Dec 2, 2010)

[ame]http://www.youtube.com/watch?v=B9zt3SF_Flc[/ame]
Check out my v8. I cnc'd the cam. I designed it in Inventor, surfaced it in MasterCam. I lathed the bearings first, then clamped it in a v-block like fixture to the mill table. I surfaced the top half, turned it half a turn and surfaced the other. I used an 1/8 ball end mill for a tool. I'd have used a larger one but I had to work close to the bearings. I tried to surface it in quarters but had trouble with it warping. I had 5 bearings. I didn't use 5 clamps and I should have cuz its not perfect. The cam bearings are 3/8 dia, the base circle is 1/4 and the lift is slightly less then 1/16. For material I used 12L14. Seems soft but its lasted 6 months and I run it every day. I use a flat 1/4 inch hardened lifter. Here's a tip, for long tool life in steel always climb cut. Thats important cuz cutting one side of the cam takes a couple of hours or more. Also, I got the best finish cutting parallel to the center line of the cam as opposed to around the cam. I might be the only guy on the forum to ever CNC mill a cam. If anyone else has machined a cam that way I like to hear from them. Good luck.


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## stevehuckss396 (Dec 2, 2010)

QSPSB  said:
			
		

> Hmm are you sure about the degree? I was told i could even go with an 278 degree duration with a 0.490/0.480 lift... Reason being.. It's a two lobe blower rotor...



I'm pretty sure. Some blower cams tighten up the overlap to keep the fuel from blowing thru the cylinder under high boost. The blower on my chevy only made 10.5 lbs boost so i stayed with the 110 centers/ 270 duration/ 714 lift and made 1224hp and 990ftlb torque. When the pedal was on the floor the last thing on my mind was how much fuel was being wasted.

The cam in my Peewee is 110 lobe seperation with 280/280 duration and .070 lift. It runs well but I would like to know how 300 or even 310 would sound.

[ame]http://www.youtube.com/watch?v=1-JRQGPswVA[/ame]


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## dvbydt (Dec 3, 2010)

Awesome engine bay Steve! If it moves - oil it, if it does'nt move chrome it! On a more appropriate thread, I would show you my Triumph Spitfire bay that took first at the International Weekend.

Cam profile should ideally be a sine wave to take up the clearance (lash?) swift rise and slowdown to the peak. This keeps the acceleration low and reduces the loads on the valve gear to a minimum. Though on a minature engine it may not be so important.

I use DesignCad for drawing. It has a plug in, ContourCam, from Magic Systems that could handle a camshaft (or crankshaft). With Mach3 and a 4th axis, I am sure it would be doable, but I am not committed enough to try it yet.

Ian


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## QSPSB (Dec 3, 2010)

Awesome engines guys... And thank you for all the help guys.... I am currently converting my X2 mill over to cnc so i still have a few months to figure out the cam software i may need to purchase... I currently do the majority of my CAD work in Solid Edge 2D and CAM work in Sheetcam... I have Mach3 installed on my computer but haven't had a chance to play with it yet... I suppose once i get the mill steppers installed and all wired up I'll need to learn how to set up all my ports/pins and such then... I actually can't wait to get it all converted... It gets quite old turning these wheels by hand real quick...

396> I'm a loving your 69 Chevelle...I used to have a sweet 68 SS when i was young... It had a 396 4 bolt main block... dual 750's on a tunnel ram intake.. with a muncie 4 speed close ratio trans... 12 bolt 411 posi rear end... she was super quick... unfortunately it was stolen and never recovered....

Guys feel free to post your engines/cars pics here... I'm a gear head and just love it all.. no matter the scale..

Here's another project I'm working on.. have been for 3 years now... I just got the new chassis under it and I'm awaiting the new motor & trans... I'm going with an JanCen 526 Aries solid block. Bruno/Lenco 10'' triple clutch 3,4,5 speed... She should go low 6's or so...


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## Joachim Steinke (Dec 3, 2010)

A real CNC driven cam grinding system will be a nice to have for most of us anyway, but thinking of the immense effort for such a infrequently used tool in our hobby workshops makes me doubt about the real need. 

I dont want to discourage someone nor talk you out of your ambitious plans, but for most of us normal guys the realisation of a real CNC grinder will stay a dream. So I want to show you some sort of middle course between pure CNC grinding and filing your cam lobes by hand.

Naturally its always a matter of taste and engine performance that determines the complexity (and the machining effort) of our cam profiles. First of all, I assume that we want to grind the cam shaft more or less precisely from hardened material. Otherwise offset turning with an eccentric fixture or offset milling with a boring head and a rotary table will do the job on soft steel as well. Step by step milling with the front side of an end mill, holding the shaft in some indexing fixture, is another common method on soft blanks. But this can get a real boring procedure, depending on the amount of iterations you might need according to your consideration, I would say too boring for meha ha ha.. 

Okay, we intend to grind them from the real hard stuff.

I think harmonic three radius lobes will be sufficient enough in most our cases, so asymmetric or even undercut profiles can be disregarded here. I dont use special software for cam design (dont have one), I generate the profile with a standard CAD program and then mostly check my design with the Cam Milling Data Calculator from the model engine news page: 

http://www.modelenginenews.org/ ..have a look at / Resources / Design Centre /

I dont need the lift table from this calculator, at that stage I already have the poly line that describes the profile received from my CAD and that is all I need. But Rons calculator is a really nice tool to get an idea of the valve acceleration too.

They are still three radius profiles and could be manufactured with all the standard milling and turning methods on soft steal described above as well. But we should have an eye on some valve clearance too. One method to regard the clearance without decreasing the desired action angle is enlarging the manufactured cam angle. But this, when leaving the base circle, will shift the contact point of the follower more or less away from the correct tangential transition which can result in some heavy and unwanted acceleration. 

The other method is keeping the original timing angle and giving tappet clearance by undercutting the base circle, it is used for the design of my two example lobes here:








We need a suitable junction from base to flank circle now which can be easily drawn with a transition curve followed by a short tangent leading to the new base circle. The only problem is this little section of our cam profile can not be manufactured with the standard milling procedures listed above. 

But as I intend to use my pivoting cam grinder system I only need some simple flat master lobes made from suitable sheet material. Such masters can be milled precisely enough with a standard CNC miller, even a small table top routing machine should do that job (we like to call them cheese mills in Germany.ha ha ha). 

Our cam shafts are no big ones, normally something about 0.3 or perhaps 0.4in of diameter. Larger masters are easier to mill and better to handle on the cam grinder, so I enlarge the masters up to a base circle diameter of 1.2in in general. 

This is done with the offset function of the CAD, which leads to some funny shapes. But dont use the varia or zoom function, maybe it looks right to you at first sight, but the grinding results are not usable! 








The cam grinder follower system will generate the correct shape from the ugly lobe as you can see on this drawing:








I make the masters from 4mm solid HPL (high pressure laminated) board, this material is easy and precise for milling and it is hard enough for the job on my grinder. But naturally, especially if you want to go on cam shaft mass production, you can take brass or steal sheet as well.








To increase the entertainment value a little bit, two additional videos of the master production.ha ha ha.:

http://pl-hi.de/JST/Cam-Grinder/Cam-Grinder_04.mpg

http://pl-hi.de/JST/Cam-Grinder/Cam-Grinder_06.mpg

And the finished masters













ready to use on my small cam grinder which I already showed here some weeks ago:














Okay, I admit this method requires some sort of CNC machining too, but you only need a standard CNC, no very rare and special machine. I think its a really convenient and fast done process and the results are reliable and precise enough for our needs at all.

Achim


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## QSPSB (Dec 4, 2010)

Holy Smoke.... Sir you are quite talented... I'm not planing on building a to complicating cnc machine my friend... It's just a Sieg X2 Mini Mill....I do plan on putting together a few CAD/CAM programs together for the cams though... I don't plan on mass producing any of my engines but i do want to cnc machine quite a few different lift/duration cams... as well as small block v8 cams... I think once i get my head into it I'll have no problem creating the proper G-Codes to do such precise work....


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## dvbydt (Dec 4, 2010)

Steve,

If you want a blower cam profile look at the RR Merlin V12.

http://en.wikipedia.org/wiki/File:MerlinHead.JPG

This is a re-entrant profile. The problem is that valve acceleration is very high, think hitting the valve stem with a very big hammer, even RR had wear problems.
Raiding my box of "This is too interesting to throw away" I came up with this cam from a pre WW2 Austin Seven. You can hopefully see that it is also re-entrant, with 1.5 ins radius on the flank. It too wore badly.

Ian


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## dvbydt (Dec 4, 2010)

OT but you did ask. Spitfire 1500cc engine bay, the competition and the trophy. Can't match American Iron for bling, it was 30 years ago, but I was a very happy bunny that day!

Ian


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## dvbydt (Dec 4, 2010)

Achim,

I am constantly overawed by what you guys achieve in this group, that cam grinder is splendid!
I made an overhead camshaft glowplug engine years ago and faced the problem of how to do a small camshaft. The rather crude way I solved it was similar in principle to your grinder, in that I made up a template like yours to fit on the back of my back plate on the lathe. It was just rough machined, marked out and filed to the profile that I wanted. The cross slide was disengaged from it's nut and a ball race used as a follower on the template, this was kept in contact by means of a tension spring at the back of the cross slide.
A tool post grinder was mounted on the auxilary. The spindle was turned by hand and the auxiliary slide used to apply a cut as the saddle was traversed back and forward.

An amusing gotcha was that the engine would not start. I had designed the cam for car engine rotation ie clockwise from the front. Most model aeroplane engines run anti clockwise. Anyway a pusher prop solved the problem!

Ian


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## HS93 (Dec 4, 2010)

dvbydt  said:
			
		

> OT but you did ask. Spitfire 1500cc engine bay, the competition and the trophy. Can't match American Iron for bling, it was 30 years ago, but I was a very happy bunny that day!
> 
> Ian



Nice, they are all to clean for me

by the way is the fuel pump missing ?

Peter


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## dvbydt (Dec 7, 2010)

Peter,
Yes that bay picure was during the rebuild without the side panel, it was never as clean again, the pump was off for plating and polishing. Here it is with the pump!

Ian


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## johanneskees (Aug 31, 2012)

I am also interested in the formulas to work out the cutter paths. In the meantime I built a "copy a master cam" type of camgrinder which gives exelent results.


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