2 cams look the same but one isn't a ramp cam

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Simon.Gardiner
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Re: 2 cams look the same but one isn't a ramp cam

Post by Simon.Gardiner »

Vincent.vanGinneke wrote: Wed May 03, 2023 10:15 pm few years ago I bought an new 'VCH' cam, made by Newman cams for the AOMCC....
Vincent - have you managed to get the wonky pump-drive spigot fixed on that Newman cam, or maybe you're going to chop it and use a Morgo gear pump?
(I've got one of those VCH cams as well, I was going to use it with the Morgo but they've been out of stock for ages and I'm beginning to wonder if they will actually get a new batch made.)

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'55 Huntmaster, '56 VH, ' 51 VH, '62 Arrow, '80 R100RT, '00 Sprint ST (now with a new Arrow project, and just now those 4-stroke Ariel parts can't even make one running bike...)
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Re: 2 cams look the same but one isn't a ramp cam

Post by david.anderson »

Ian
The 51 cam is actually a cast steel cam without the hole.
With at least one Ariel part the letter A was stamped on it to signify a change. I have two 1949 oil pumps, one is stamped 49 and the other is stamped 49A. The 49 pump is the small delivery plunger and the 49A pump is the larger delivery plunger. The upgrading of the oil pump was mid 49 and clearly the 49A stamping signified this, although the larger plunger did make the change obvious. So as you state possibly the A stamping was an early identifier, even though the difference between cams could be identified by the lobe hole. I have checked 4 of my available 54VH cams not in a bike (all have a ramp) and none of them have the A stamping.
The one sure way to know is to check the cam lift with a dial gauge while checking degrees of engine rotation. The ramp on the Ariel cams is very long, in fact much longer than used by modern cams. The initial .006” of lift (tappet clearance) occurs over 40 degrees of engine rotation although the total ramp is actually around 70 degrees of engine rotation, which is also fairly consistent across the competition cams.
Also not all cams are exactly the same as there are machining errors. I do have a twin lobe A7/642 cam that has a larger base circle than it should at 1.010” and it also has a greater duration than any other A7/642 that I have checked.
David
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Vincent.vanGinneke
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Re: 2 cams look the same but one isn't a ramp cam

Post by Vincent.vanGinneke »

Hello Simon, yes I got it repaired by Newmans.
I can see that someone used a heavy punch on the excenter too straighten it.
My first idea was to get it grind undersize for straightening but I guess 'they' at Newmans know best.
It took very long to get done.....(a year ?)

Long ago I installed a Morgo rotary on a single but it delivered way to much oil for a roller bearing engine.
I refitted another cam as after installing a rotary there is no way back with the cam you use :)
Morgo knows this also and since then is making larger plunger pumps (already years ago)
Through the grapevine I have heard that these also deliver too much, do they still make these ?
Anyway, Ariel knows best, a late original pump would be the best for normal use. ;)
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Re: 2 cams look the same but one isn't a ramp cam

Post by Ian.Taylor »

Thanks for all the replies, Both cams seem to have the same profile.
I'll try and get a Photo of the left cam in a day or 2.

I guess I'm more curious though the profile looks the same why does the Left cam require Nil & 002 .
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Re: 2 cams look the same but one isn't a ramp cam

Post by Simon.Gardiner »

Have we got some confusion about what a 'ramp cam' is here??

Vincent - I'll PM you about the Newman VCH cam, mustn't be naughty and do too much 'off topic' !

SG
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'55 Huntmaster, '56 VH, ' 51 VH, '62 Arrow, '80 R100RT, '00 Sprint ST (now with a new Arrow project, and just now those 4-stroke Ariel parts can't even make one running bike...)
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Re: 2 cams look the same but one isn't a ramp cam

Post by Vincent.vanGinneke »

Now and then I feel very 'Off Topic' myself :lol:
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Re: 2 cams look the same but one isn't a ramp cam

Post by Ian.Taylor »

Here are the 2 photos of the cam.
you can see there is a slight dip in the middle of the lobe.
Thoughts
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image0(2).jpeg
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Re: 2 cams look the same but one isn't a ramp cam

Post by Vincent.vanGinneke »

The Newmans cam .
VCH cam by Newmans.jpg
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Re: 2 cams look the same but one isn't a ramp cam

Post by david.anderson »

Ian
You will not reliably see any difference between the 51 non ramp or 54 ramp cam profiles by visually looking at the cam profile. And when comparing two similar objects visually, even if they are exactly the same , the eye will perceive differences, ie an optical illusion. It has been standard practice in the cam grinding industry to grind .006” or a similar small amount off the base circle and to morph (blend) the flanks. This will slightly increase lift and duration, and although such changes are not visible to the naked eye, such a change may yield a slight increase in performance. So cheating along those lines has been common in production racing. Many cam grinders still provide mild street grinds along those lines in cases where they do not have a master blank, cnc program and for generally uncommon vehicles. The only accurate way to check the cam is by measuring lift with a dial gauge v engine rotation degrees, and even then there may be minor differences in original equipment due to machining processes. CNC has changed all that.
Vincent
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 do know that a cam designer did have dealings with Newman cams and also the cam designer had access to the original 1952 VCH cam detail. That same designer provided me with a computer analysis that showed almost 2 hp more with the VCH cam over the single lobe VH cam.
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Re: 2 cams look the same but one isn't a ramp cam

Post by nevhunter »

Having separate lobes will always facilitate getting the optimum timing and the followers are lighter. The advantage of the wider ones is there is less wear generally. The speedway JAP (another Val page design) has rollers and very light followers with more staggered pushrod covers. The round base VCH ( electron cased earlier model) has two lobes and the same cam as the normal VH. Nev
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