ET: Engine (Twin) Quieting ramps / Andrews Mk 2

[oexing]

Recently there was some discussion about quieting ramps on Vincent cams. A few days ago I put one genuine Andrews Mk 2 cam on my test rig for camshafts for checking it about any quieting ramps. When you know how to look at them you can detect them by eye but actually there is not a lot on them. I´d say about 0,20mm on the camshaft which is a bit more via levers on the valve as my jig got no lever follower for getting lifts. I had a plain follower on the Sony encoder that is why the diagram looks a bit weird with the non-symmetric shape. But this is exactly what it HAS to be when a lever is in the business. Any obscure camshaft that looks symmetric will be WRONG in a Vinecnt engine as it will not fit a lever follower, no matter if plain or radiused. Just a cam for a radius follower appears a bit more symmetric and rounded.
This test was NOT to show valve lift curves, just for checking for quieting ramps. And when it comes to this it is essential to keep zero valve clearance in cold all alu engine and steel pushrods. Unfortunately I expect with steel pushrods you will get a bit too much valve clearance with a hot engine and the modest quieting ramps will be pushed out of business then and some more valve clatter and additional valve gear loads will act on all components in there.
This was one of several reasons why I went for 10x2 mm alu tubes for pushrods like I have on most engines in my garage - and a lot longer than the Vincent sizes. So then I will see if zero clearance is suitable or I set some small clearance when cold - by listening to valve ticker when hot.
Anyway, when chasing for new cams I´d like to point to Andrews/ Megacycle cams as I believe they will be the best bet and I would not have any faith in reground cams from unknown origine - could turn out to an expensive learning later.
I got all Libre Office numbers from my test jig but would not know how to post them here, unless I do a number of screen shots, on demand certainly.

Vic

Max lift in the diagram is 8.45 mm, so a Mk 2 type:

A failed Horex "sports" cam:

 

[greg brillus]

Vic, Interested to know how you figured if the cam bore is hard enough to run needle rollers......On our roller cams, we had them induction harden them and then hone to size.......Only time will tell if it survives......Of course with roller followers we are running much higher spring pressures than stock Vincent springs.......If your cams and followers are good, they won't show much noise........you tend to get that from any play in the head/valve gear........loose rockers/pins are the culprit there.......Tight spots in the gear train tend to make a hunting noise, and gears that are badly worn, and/or too much back lash tend to sound like noisy bearings......Fixing these items is not too difficult, not near as messy as cleaning out the oil tank........All in a days work.

 

[oexing]

For hardness testing the olde toolroom checks will do, get a file with an edge or a scriber for scratching the part. The Andrews came with gears pressed on and the bores were quite hard, suitable for all those needles. Basically down to 58 HRC no reduction of calculated loads is necessary, the lower you go with hardnesses you have to factor in less loads. But you could run needles on alu spindles with clean oil and low forces. Like with Laverda 750 twins, they got high tensile conrods, but not like 60 HRC or hardened liners in the big end. But they did extra wide bigends plus two each alu caged roller bearings side by side, exactly same bearings like in the 600 cc Earles BMW R 69 S, running on a 36mm crankpin.
These crowded needle bearings in my camshafts are a factor higher load carrying than the rest of the valve train, don´t confuse that type with common needle bearing assemblies with cage and inner race. The inner race will have quite thin spindles then and the space for the cage offers only half of numbers of needles and shorter too, so maybe only one third or less of loads a crowded type would take.
Would you share a photo of your roller followers - or are they secret tech that no competitor may find out ? I see the limit of all loads in the valve train in the bearing of the roller follower: You can have a bush or just hardened faces of spindle and roller in there, for racing it will do a while. But for road use it will not last very long, you really want crowded needles in there, nothing else will do high mileage. Certainly all bearing components will want 58 plus HRC for needles.
High spring forces actually matter only while at low revs and tickover. At very high engine speeds there is near to no spring force on followers, no matter how aggressive the cam lobes may be. You will be happy to have any small load at all on the followers at that speed as the valve train is wanting to leave contact on the cams from acceleration stage before. All extreme forces on cams and all are based on masses of all components that get shifted in valve lift. So low weights are what matters most in high revving engines, not the spring forces which just care for keeping contact on cams and prevent valve float.
Again, an argument for alu pushrods, 29 gram , 40 gr the steel originals, heat growth the other matter.
Not keeping valve clearances in limits will show well with air head BMWs, they will get quite noisy once too much play is set as in consequence the quieting ramps will become uneffective and acceleration of valve gear gets harsh and damaging on components. That is why I´d like to draw attention to valve clearance matters. Other flaws in timing gear are certainly a thing to watch and work on.
Greg, did you ever check for valve clearance on a hot engine right after killing it at home ? Certainly provided you set it for nil at cold first . The 460 cc Regina with all alu engine and alu tubes would like a bit more heat growth of pushrods when hot but I cannot think of any idea how to achieve this - and I will not go for some hydraulic gadget in there.
Below my modded roller followers from prewar Horexes, the 1935 Guzzi got same treatment with needles more than 30 years ago, did 30 000 km since.

Vic

 

[ilikevelos]

Nice test setup and very interesting topic. I understand the value of quieting ramps and that they make clearance setting more critical. I am relatively new to Vincent but understand that the clearance at running is created by differential expansion between the al and the stainless pushrods. I like the weight savings of aluminum pushrods but are they practical for the street? What does the use of the aluminum pushrods do to the setting of valve clearances? And how is this measured with the hemispherical ends at both pushrod ends. Do you need to take timing cover off and measure between cam and follower like a thruxton velo?

Thanks in advance.

 

[bmetcalf]

With the stock pushrods, clearance is zero and the pushrods can still spin easily. The adjuster thread is 28 tpi, so one flat of a turn is .006". If you choose to have a clearance, you set at zero then turn it one flat for .006" and interpolate for a different clearance.

 

[oexing]

Vincent pushrods are no stainless steel as stock but stainless would help a little with heat growth. What do you mean with alu rods for street use ? They got hardened ball ends pressed in, like the looong pushrod at top in the photo above. This is a Horex Regina 400 original. Second from top is a stainless pushrod from the /5 series BMWs , very heavy. They went to alu pushrods later, with quite long steel exstensions with ball ends pressed in - not my idea like these. Anyway these were in the 1000cc R 100 RS with 70 hp at 7000 rpm plus !! So my short alu rods are no more headache for me, you´d never kill them on any Vincent, there are other places that would go first by a long way. Just the way you assemble the engine is a bit different: You cannot drop them through the rocker adjuster thread like is common here. Instead once the cylinder is on the case you drop them onto the follower ball cups down there and with some wiggle put the head over the lot with the pushrod shrouds - easy. BUT clearance in the shrouds has to be made for the 10 mm tubes: The recesses for the shroud seal were machined offset from the ball cup in the followers - which nobody here has ever commented, was obviously never set right at the factory. So I made offset o-ring seal holders that moved the pushrod shrouds by one millimeter in the more suitable position to go with the followers - nice lathe job.

Vic

 

[greg brillus]

We run 5/16" hollow chromolly pushrods with the ends pressed in........with our roller followers these are not much more than 100 mm in length, and way lighter than the stock Vincent ones.......With tappets set to minimal clearance cold, the hot clearance opens up somewhat.......actually more on the exhaust than the inlet.......alloy pushrods could give clearance issues.......only testing would find out what to do there.......Most all of our parts, the pushrods, follower rollers,pins, needle rollers......the beehive valve springs, titanium retainers and so on are all from LS Chevy V8's .......No need to prove their running ability........probably the most successful alloy V8 ever made. I'll try and load some pics on here, but i'm not great at that stuff......

 

[ilikevelos]

What i was really asking was if the expansion of the al pushrod required a looser cold clearance. How to get an increased clearance is obvious after Vic explained it. You guys are at a different level from me. I can put an engine together and run a lathe but you mods are far beyond my skill level. Thanks for the explanation.

 

[Vincent Brake]

Its not only about the weight. But the shortning under stress. Here steel is better.
Alu 1/3 as stiff at same diameter.
Maybe Titanium. At 1/2??
Oh don't forget the buckling effect.

 

[oexing]

Vincent, you are quite right on the properties of alu: The E-modul is one third of steel so when you need same stiffness you have to design for 3 times thicker components. So as specific weight is one third as well you end up with a component with same weight like the initial steel component - so no weight benefit by having alu.
When elastic deformation is not a problem you can have parts at much lower weight with alu.
The alu tubing used by BMW or Horex got 2mm wall thickness so these are quite acceptable for that job. The R 100 RS got looong pushrods, twice as long than Vincent types. Yet they do 7000 rpm plus for 70 hp, some flex is expected certainly but they hold up allright. This matter is no concern with the very short Vincent tubes I did , extremely unlikely to buckle them. I got some titanium tubes , did several components on my HRDs in titanium but would not accept this for pushrods as heat growth is miserably low - just not what I had in mind.
I found very thin walled stainless tubing, that would be better than high tensile steel as heat growth is better than carbon steel but a lot less than alu. Sofar no better ideas here about any other material for pushrods.
Just for adding to the matter, the sports BMW R 69 S had extremely lightweight thinwalled CrMo steel pushrods with brazed on ball ends to go with cast iron cylinders, alu heads, plus rockers mounted on top of long steel pillars reaching down near the head gasket level so the actual aluminium material that may effect heat growth and fucking up valve clearance by a hot engine is only 15-20 mm remaining. So by that trick they got away from noisy engines in hot condition even with no alu pushrods in them.
And certainly crowded needle bearings in rockers as standard on sports types, just I had smaller needles, were 3mm, now 1.5 or 2mm after overhauling them at maybe 100 000 miles - ahhm, converted from kilometers of course, never got mileages out of them . . .
Since 1980 I got alucylinders too , 730 cc then, but kept the steel pushrods. So all I can do have zero clearance in cold engine - like Vincents - and accept some minimal noise from extra clearance when the thing heats up. But then the Schleicher camshafts are according to modern knowledge well designed with quieting ramps certainly.

Vic