so...reading the post/thread on that Vari-cam gear reminded me of the much-ballyhooed Dual Lobe camshaft that was being advertised back in the 60s. I was doing sports cars at the time, so I never had a chance to check out anyone that ever tried one. Anybody here have any experience (good or bad) with that concept and the product?
Bus Schaller first made them for racing Harley Davidsons. The theory was to reduce friction by driving the cams at 1/4 engine speed instead of 1/2 engine speed. He claimed the slower speed also allowed the lifter to follow the cam easier. Roller lifters reduced friction, and were necessary. It would have been impossible to use a flat lifter on the smaller cam lobes. Whatever happened to them I don't know. Now that I think about it, I'm surprised the auto makers never took up the idea. For years now they have been trying to reduce friction by using roller cams anyway, and any other idea they could find.
That dual lobe inverse cam takes too long to grind and would use one wheel stone per cam. A standard Norton can take a 24" stone because the lobe is egg shaped, on the Schaller because of the inverted flanks maybe a 2 1/2" stone and would wear very quickly, Again maybe it was a two step grind, but that adds up in production time.
I remember the day I snapped that picture many years ago. I looked for 8 years for a complete kit which I found on eBay.
I used a belt over a 1 inch steel contact wheel to grind Allison cams in the 50's. I could get 2 cams per belt.The depression in the flank was .030 deep.
I think another reason the 1/4 speed cam disappeared is the rapid increase in lift numbers in the sixties. I dont think you could grind a double lobe cam with .400-.500 lobe lift unless you increased the cam bearing journal size a LOT. Then you are into an issue with rod clearance. Great idea that time/evolution passed by.
Auto manufacturers could solve these problems by increasing the diameter of the cam bearings but that would lead to more friction. OHC engines that do not need to slide the cam in thru the bearings, would not need to worry. So, I still don't know why OEM manufacturers never tried this. It seems a simpler way to reduce friction than some of the things they have tried. All I can guess is, it didn't reduce friction or not enough to be worth the bother.
Harleys had roller lifters from the factory starting with the knucklehead in the '30s. Single lobe cams. I do accept the reduced friction of running the cam at half speed though. What happened to them was that it was too pricey for the results which were non-results. They didn't run any better then a standard camshaft. and to run one it was more than a cam replacement it took a doubler to run the ignition as well as the new cam gears and cover.
A lot of wierd stuff was concocted in the "old days". Here's a pic of a 6 cycle cam prototype that turned 1/3 engine speed. We developed this engine from a 455 Pontiac and later applied the technology to the 4 banger Pontiac. The engine had a normal 4 barrel carb but also had Bosch type injectors through the side of the cylinder wall at top. The engine ran normally through intake, compression, power, exhaust cycles except when the piston came up on exhaust the valves stayed closed and fuel was injected in with the hot exhaust gas for another power cycle. Hence the name "6 cycle engine". It was very successful design and was used in portable mining power units that could be dropped into remote mining operations by helicopter. Crower was working on a similar engine design around the same time (late 50's) but never did anything with it. I tried to talk to him about it once but he thought he had an exclusive design and wouldn't talk about it....lol
Bruce was like that... He was nice to me, never a bad word, or mood. RIP... they made me a cam (once) and we called it the/ a "OSCAR GRIND"... the back story is long... i'll get to it later...
gee....(tongue firmly in cheek)....sure wish there were smarter guys on here. Thanks to all that responded - my question was answered in its entirety and more. dj
My father went to grade school with Bus Schaller in Pittsburgh Kansas, and continued contact with him for years after. I will never forget my 13th Christmas, and receiving a "quarter speed" t-shirt that was 2 sizes too big, but all the more wear time! Man I sure wish I could find a logo or template!
Oldest Harley I owned was a 1929 flathead 45 and it had roller lifters. I believe they all did from the first but can't prove it right off the bat.
Years ago a lot of the higher end passenger car engines had roller followers or hard face cams and followers. That was done because the oils of the day weren't very good at lubricating cams/lifters, especially with anything other than very conservative grinds.
The Jalopy Journal
