Ariel Owners Motorcycle Club

Bob.Murphy wrote:The JAP single appears to have an Atmospheric Inlet Valve, will the 'V-Twin' have the same ???

No, it's a push-pull desmodromic system, that's why the tube is so long to give the rod space to move at the camfollower, but I don't think there is an advantage to atmospheric becouse the exhaust is closed some time before the inlet opens.

Indian ran a "hacksaw" mechanism that did the same thing in it's early days. Early "F" head motors were often derived from atmospheric inlet valve engines by simply adding a cam and pushrod/rocker mechanism. The timing was often such that the inlet only opened well into the piston downstroke, until later years when the more radical timing proved to deliver a lot more power. Nev

nevhunter wrote:Indian ran a "hacksaw" mechanism

Could you show how that worked?

Direct on the exhaust and the inlet was opened by using a heavy spring against a lighter one which it overcame. You could even claim it was desmodromic since the cam shape produced a positive action by each valve. The term "hacksaw refers to the frame resembling that of a hacksaw pushing the exhaust open and pulling down on the lighter inlet spring and opening it as well later on, in the cycle. It was only used for a short while, being replaced by conventional cams for each valve and a rocker on the inlet. Pages book probably has some reference to it. It addressed bikes up to 1915 with mechanical features being explained, for various makes Nev

adrie.degraaff wrote: No, it's a push-pull desmodromic system, that's why the tube is so long to give the rod space to move at the camfollower.

Thanks, I had wondered if it was a see-saw mechanism that pushed & pulled the valves, but couldn't really make out the detail. It just goes to prove that "There is nothing new under the sun" .

So what will the V-Twin have ???

Bob.

Bob.Murphy wrote:So what will the V-Twin have ???

Not sure, I made a drawing of the cam and be tempted to make it, maybe try all and see what happens, this being my last project.

Like this ? this pic is all I could find on the net.
Would be nice to see the whole mechanism.

It was probably made for only one year. The single cam has to lift a strong spring as well as the exhaust one and when the inlet is to open the cam goes further closed as far as the exhaust is concerned (but is not attached to it) so the inlet is opened by the stronger spring and the exhaust just has more clearance. A drawing would explain better but I don't have one at the moment.. There cannot be any overlap with this method. Atmospheric inlet valves carried on well into the teens, with some makes( Merkel 1913.) Nev

Still can't work out the 1.5 stroke where both valves are closed.

Here how Ariel went from vacuum to MOIV with a one lobe cam for both valves, the 1908 club Ariel should have this aswell but as it was missing parts some one invented (sixties?) the desmodromic sistem it has now.

Here you have a 1 3/4 HP vacuum Ariel-Minerva 1901-1902, a 2 1/4 HP vacuum 1902-1904 and a 2.5 HP MOIV 1903-1910.