Camshaft

[quinnf]

Anybody know what a British cam looks like?  Pinned lobes or one piece?

Quinn

[oliver90owner]

Look in the parts listing book?

Regards, RAB

[mobile_bob]

hey us yanks, don't have no stinkin parts book!

hell we would be doing good to have an original lister over here 

bob g

[JohnF]

I've got one 6/1 that is a real "hopper".  It is so bad that it broke the camshaft after 700 hours of use - that's absolutely no good to me.  I'm going to have a couple of single cams made up to see what difference it makes but I'm beginning to suspect that this particular engine has a bent crankshaft or something similar.  It has been a problem child ever since I put it in to replace one with over 26,000 hours on it - wish I hadn't!  When I put the new Injun shaft in it seemed to be a little better, but not nearly as good as the Fergenmonster (That's a 6/1 lower end with a 10/1 piston, sleeve, barrel and head attached.  It runs at 650 rpm and gives a "bit" more power than the standard 6/1, not enough to make it worth anyone's while to do it)  I just did, well, "'cause I could".....and I was bored that day......

I've just sent a bunch of Injun lobes down to my cam maker, hopefully will see something soon.  The down side is that they came already drilled, but I think my guy is going to re-drill a hole 180 degrees off from the original and use a much smaller pin.  The English one I got had pinned lobes.

[cujet]

Tig welding the camshaft lobes won't be a problem. I already weld the pins in the lobes. Same for 2 stroke crankshafts, the hardened pin welds just fine.

[Crofter]

Tig welding the camshaft lobes won't be a problem. I already weld the pins in the lobes. Same for 2 stroke crankshafts, the hardened pin welds just fine.

Cujet, I agree that TIG welding would be the way to go but I think there would be serious concerns with distortion or weld zone embrittlement if you circumference welded lobes to the shaft under field conditions. I have seen welds pull out intact from high carbon steel and seen fatigue fractures start at weld edges. Certainly to fabricate a camshaft assembly by welding on all the elements instead of pinning you would no longer have a straight shaft and it is going to play hell with the support bushings. It could be done but lots of unintended consequences to deal with.

I got a bit of back grounding on this in stress relieving piping welds. The training demoed grain structure of weld cross sections that had been polished and etched as welded with no pre and post heat, ones done with proper procedure and also after total stress relief heating. Quite dramatic difference. Two gas pipeline blowouts occurred north of me a few winters ago. Cause? you guessed it.....! weld failure at heat affected zone from lack of preheat.

[XYZER]

If I was having a pin shear problem on a single I would tend to silver solider them......maybe. Then have the lobes re-ground for correct timing whatever that is. Solid shaft for a twin.........

[Crofter]

If I was having a pin shear problem on a single I would tend to silver solider them......maybe. Then have the lobes re-ground for correct timing whatever that is. Solid shaft for a twin.........

That would take the torque transfer off the pin for sure. How about the hardness of the lobe surface? would that have to be re done?

I think a good part of the problem is the slack fit of the cam piece. If they could be placed hot and shrunk on like the crank timing gear they would be a better assembly. Or how about machine a shaft so it was oversize at those locations so the lobes could be press fit cold, yet proper shaft size at the bearing locations? Just think of the cost that would add though!

I wonder what construction method John F and his camshaft man are contemplating on the new design. Single or double also?

[cujet]

One of my thoughts was to simply tack the lobes in the proper position. Then run the tapered reamer through. If the mismatch is not too bad, the reamer should true the hole and allow the use of a stock pin. Which would be tack welded in place too.

FWIW, I don't expect any significant distortion using this method. The way we weld crankshaft pins produces so little heat, there is no warpage of note, and that was the basis for my thoughts. I'm not talking about a large weld bead, simply a TIG weld, done on a lathe with little to no filler.

But, it remains to be seen. So, I guess, it's "wait and see".

[Horsepoor]

JohnF,

Please continue to post updates on your cam shop down in Tennesse. I and at least one of my friends has also expressed interest in a precision / accurate camshaft for twins. Even at $300 or so, this may not be that expensive when one calculates all the damage that acn be caused when a camshaft fails and trashes the rest of the engine. So to maximize fuel efficiency and power output while almost guarenteeing the absence of a camshaft failue, it is worth it to me.

Please keep us posted on your progress.

Bruce

[JohnF]

For this run we will be using Indian cams fastened on to a North American shaft.  The jig has been set up and the cam degrees of separation exactly measured.  Each cam will be fitted/ground as necessary (we did find that the Indian cams had a pretty good Rockwell hardness index but the shaft did not) then pinned to the shaft with much smaller pins.  For this set I ordered enough cams for about 20 assorted shafts (single and double).  I'm not completely sure that the singles will improve much with the new cam, the Indians seem to be able to get it "close" for a one cylinder, although I have one very bad "hopper" engine here that is going to be my test bed on that issue.  I have just sent a couple of twins plus some old engines down to Tennessee, my guy down there will re and re the cams after testing with the originals in place and do some real-time data logging.

I sure hope this works with the twins, I had stopped importing them because of this problem.  However, this is a relatively easy fix (if not cheap!). If it works, so it will open up the possibility of bringing in the twins again for me.

The cam maker does not want to TIG or MIG the cams, I haven't discussed why with him, he's the expert!   

[Crofter]

Cujet, I agree that several small tig tacks equal in size, opposite, and laid down in opposing direction, would not likely be a problem for distortion, but as little heat as you can use will still far exceed the transition point though and if the shaft is anything other than mild steel it will leave a hard spot that is a stress riser seed for potential crack propagation.  I think John F considers it likely that the drilled pin hole in the shaft is effectively creating a notch that leads to breaking from gradual crack propagation from this point. My guess is that is why a smaller through pin is being considered. I have heard of pins shearing on the timing drive gear so there may be a limiting factor then with how small you can go with the pin size.

There is a big difference in toughness in different alloys especially in regard to fatigue resistance so John can likely make a big difference there in potential life of the camshaft assembly.

Torsional resonance phenomenon may be a factor and the sharp power pulses of one and two cylinder low speed engines could be initiating forces at just the right frequency to create a problem. Do a google search on   torsional resonance   for some interesting reading; that is at the root of a lot of shaft failures. Cummins had the problem 20 or more years ago with breaking crankshafts. If you held them at just the right frequency they would break in short order! I think I have seen Mobile Bob post about that. I ran into it in some prototype logging equipment being tested and it took a while to sort out that it was not operator abuse causing the drive shafts to wind up.

[XYZER]

I suppose any heat applied will introduce a problem......I remember when I was a young know it all I had a Ford 1/2 ton with the pressed on collar that helped hold the bearing on the rear axle. I had a iffy one and just put a minute tig tack on the collar to hold it on the axle.....boy that was a long hike!

Hey Johnf is there enough size on the cam lobes to bore them out and go to 7/8" dia? Stock is 3/4" i think.

[Apogee]

The right way to do this imho is for the cam grinder to locate a cast iron blank that can be modified to fit and grind that.

When I spoke with my local cam grinder about it, he figured he'd be able to find something that could be modified to fit.

No pins, no welding, hence no stress risers...

Short of finding the correct blank, I'd key the shaft and lobes for the correct location, and put a snap ring on either side of the lobes to hold them in place.  Yes, it would be a bit of a challenge to figure out, but it would solve the problem for good I would think.

I would submit that the only reason those lobes are being pinned is to save money.

These cams just don't have that much force on them when compared to modern V8 engines so I think it would work fine.

Just my $.02,

Steve

[rcavictim]

I am a bit puzzled why it appears to be hard to find a cam manufacturer who cannot duplicate what has to be the most simple engine camshaft in the world, and one that operates at very low stress and lifter contact load.  I'll bet you could make one yourself on a wood lathe and disc sander in one piece out of hard white maple or even teak that would last for a while.

What's wrong with these Indian engine manufact-errors?  If their product line required more different grinds than just two, one for all the singles and a different one for all the twins, then the slide on hardened lobe secured with a pin and pre-cracked at the factory with a oversize hammer precisely applied by an uneducated laborer might make some sense.  They could make a case for stocking only one bare shaft for each engine line, adding the lumps as needed.  What they do now is supply custom timing profiles, not by design but by incompetence.   

Perhaps we need to inspire the interest of one of the well known North American cam houses like Isky or Crane to make a limited production run of one piece camshafts for these engines.