Ariel Owners Motorcycle Club

David, indeed, the ramp has a curve. I think this is a positive thing.
I've 'found' in my pc a diagram :
also a drawing from Mr. Hartley showing a twin lobe cam grinded down too function as an single lobe.
pretty whopping !

I have what is believed to be a Hartley cam on EBay at the moment, will check it against the drawing above

Vincent
I have a copy of that diagram and cam photos supplied to me by John ?. As you can see from the diagram that you posted that is a very severe cam with virtually no opening or closing ramps.

Pete here is a couple more Hartley cam graphs and these are the cams referred to by Paul Jameson in his article. There are apparently numerous Hartley grinds. The 164B was purchased directly from Hartley by Chris Reynolds. The second cam came from a Mr Pratt which carries the Phil Joy number 164A. Apparently Phil Joys records indicate that the 164B is listed on his records as a Hartley grind but he has no record of where the 164A grind originated other than it was supplied to him by Chris Reynolds and was referred to as the Pratt cam. However cam designer Ron Herring having studied the cam has no doubt that it is a Hartley design. Brenton Roy who used to frequent this forum managed to borrow the cam and had it copied by Franklin cams in New Zealand and last I heard it was in his bike.

On a further note I have machining coordinates for the 1952 VCH cam that were provided to me by Ron Herring. His notes state ” These are the X and Y co ordinates that can be fed into a CAD program as an .iges file or similar. The CAD software splines the profile point to point to provide a smooth tool path for the cutter. You can also view the profile by loading the file into Excel and creating a graph from the two columns of data. ( Load the file as 'comma delimited ', the file is in .txt format, but to convert to a machining file simply rename it to a .csv or .iges suffix).
To machine a single cam we load it onto the table of a vertical mill, and rough the profile with a 5 flute roughing cutter, then finish to size with a new cutter. Made in a nitriding steel such as EN40B, there is no need for a finish grind to size if the cutter finish was carried out correctly. We then nitride harden the cam using a gas nitriding process that does not distort the cam.” If anyone is interested I would be happy to provide the .txt file.
David

For those interested, the EBay reference is: www.ebay.co.uk/itm/295684983946

Not really part of the original topic but it is part of the VCH discussion so I'll post here.

david.anderson wrote: ↑Mon May 08, 2023 8:42 am ...That cam does not appear to be to the original VCH profile diagram. The original diagram shows the cam flank is straight between base circle (.050” rad) and nose circles (.0406” rad) apart from minor blending at those circles. Your photo shows the flanks of the cam are slightly curved. So have Newman improved the original profile....

I've just had a chat with Ken Newman, the profile they've used came straight off a cam that Pete Kemp provided, they didn't change anything.
So this new 'VCH' profile is a Kempie special (although Ken did say they'd be quite happy to take any credit if it turns out to be a good 'un! )

SG

Pictured is the VCH cam against a tracing I once made from a standard single lobe (red line) and a HS MkIII cam.
(The drawn line looks slightly away from the cam because it's how the ball pen worked )
The final lift on VCH and HS MkIII is the same, only in the rise and fall the MkIII takes a wider curve.
How this translate in degrees I dont know.
Looks like the VCH timing comes close to the MkIII one.
A HS MkIII cam works with a shortened foot on the inlet, but I am going to try it with the standard followers.

Are you going to fit this cam in your NH so that Chris doesn't have to beg a lift from another rider when you come to steep hills? Mind you I remember my wife having to do the same thing at a Treffen, mind you we were on a VA.

Possibly.. spoiled for choice atm.
I could put it in a 1944 WNG or in iron VH engined PRF aka The Hermanator.
Leaning towards the WNG as it now has a steel crank + 7.5 cr and generally is revvier then a VH
any thoughts ?

ehhh, maybe I should concentrate on my Model C