78 replies to this topic

[Spider]

The Nose of the Crank,,,, which also just happens to be the same place that our Cam is driven from,,,,,,,

[nicklouse]

The Nose of the Crank,,,, which also just happens to be the same place that our Cam is driven from,,,,,,,

would the belts transmit the variations? so we are only talking about valve timing scatter? (in the context of the topic).

 

but yes standard has potential to introduce lots of errors in the timing.

[Spider]

 

The Nose of the Crank,,,, which also just happens to be the same place that our Cam is driven from,,,,,,,

would the belts transmit the variations? so we are only talking about valve timing scatter? (in the context of the topic).

 

but yes standard has potential to introduce lots of errors in the timing.

 

 

Belts, Chains and Gears drives all will, some more than others.

 

And yes, timing errors.

 

The right damper can go a long way to reducing these.

 

As well as saving the Crank.

[mini13]

all intersting stuff! keep it going :)

 

on my next engine ( well current build) I'm planning on using the MPI flywheel and trigger which is from the flywheel so should be more accurate.  I've previously run S dampers but thinking of going to the KAD damper, unless i can find another Viscous damper that can be adapted.

 

this is for a boosted K1200, with billet crank (std stroke ) red line is probably going to be 8.5-9k.

[MIGLIACARS]

Whos crank are you using!!

 

I use the med alloy damper never had an issue. but also as its supercharged so there is a tight belt on the pulley system which im under the impression that this dampens the crank also!

[MIGLIACARS]

all intersting stuff! keep it going :)

 

on my next engine ( well current build) I'm planning on using the MPI flywheel and trigger which is from the flywheel so should be more accurate.  I've previously run S dampers but thinking of going to the KAD damper, unless i can find another Viscous damper that can be adapted.

 

this is for a boosted K1200, with billet crank (std stroke ) red line is probably going to be 8.5-9k.

I dont think you will need to rev a boosted engine so high Im sure you will have all the power you could need low down.

 

turbo or s/c??

[MIGLIACARS]

all intersting stuff! keep it going :)

 

on my next engine ( well current build) I'm planning on using the MPI flywheel and trigger which is from the flywheel so should be more accurate.  I've previously run S dampers but thinking of going to the KAD damper, unless i can find another Viscous damper that can be adapted.

 

this is for a boosted K1200, with billet crank (std stroke ) red line is probably going to be 8.5-9k.

When you say s damper do you mean the heavy horrible ones that are sold through minispares.

 

https://www.google.c...aUl-LJK-Nv95C4A

[MIGLIACARS]

all intersting stuff! keep it going :)

 

on my next engine ( well current build) I'm planning on using the MPI flywheel and trigger which is from the flywheel so should be more accurate.  I've previously run S dampers but thinking of going to the KAD damper, unless i can find another Viscous damper that can be adapted.

 

this is for a boosted K1200, with billet crank (std stroke ) red line is probably going to be 8.5-9k.

Isnt the mpi flywheel a big heavy item!

again I use the med trigger and magic eye and again can say im impressed, no issues so far.

[tiger99]

Has anyone considered using a built up crank, like certain Citroen including the 2CV and the DS19? They had roller bearings and were very reliable. Assembly is by cooling the crankpin and main bearing journals in liquid nitrogen, disassembly by an exceedingly powerful press. The webs are effectively flat plate, of possibly a different type of steel to the journals, and there is no need for rolled root radii.

The tooling costs to make one would not be all that high compared to a forging. It is all grinding, milling, boring and some hardening. The assembly jig would be the most expensive item.

Not sure how such a thing would compare to the standard A series crank for stiffness but because the big ends would not be split there may be the possibility of increasing crankpin diameter while still avoiding clashing with the gearbox internals, and the rods would be stronger. Pistons would fit in the normal way and you might wear out several sets of those before the crankshaft had to come apart to have new journals and rollers.

Just a thought while waiting around for something. If it can't work in an A series please do say so.

[Spider]

I know my friend David Rosenthal looked at and we talked over a fabricated crank for a bit, in the end he looked in to  Cooper Split Roller Bearings on the Mains, but it was getting heavy and too bulky to also fit them on the Big Ends. As there was to be a roller on the Mains, feeding oil up to the Big Ends if a slipper was to be retained, was a major headache that we couldn't sensibly resolve.

 

Bearings with rolling elements only need a 'supply' of oil, no real pressure, but slippers need some pressure. Any pressure we would have tried to feed through the rolling elements would have been well lost before they got to the Big Ends.

 

The big issue we foresaw with a fabricated crank was to keep strength through the Crank Webs around the Crank Pin.

[mini13]

yeah dont "need" to rev it that high, but essentially I am using the K1200 cams (284 deg duration) so it will make peak power where it does...  if it ends upo being an issue then I will swap to the K1100 cams which are 25somthing degrees.

 

Crank is a specialist componets one, it was one of their first batch which has the flywheel keyway miss machinend ( not offset) I picked two up unused for 200 quid. basically a std size crank but wedged a bit, but billet and en24. its lived through 2 engines worth of abuse so far.

 

yeah the the minispares damper, I thoght the general concensus was its considered better than the standard damper?

I say MPI flywheel, realy i mean verto with the light steel back plate, its not ultra light, but this isnt a NA track car... also being turbo I'm using the verto so I can stack the clutch springs so it will handle the power I'm throwing at it.

[Spider]

I'll get a scan up a little later showing Damper vs no damper. It's a bit of an eye opener as to just what and how effective the correct damper is.

 

Rather than think of the Cooper S Damper as a 'better' damper, all dampers really need to be thought of in terms of what's appropriate for the engine, just like Carb Needles and Ignition Advance Curves, though there's a broader range of what you can get away with in regards to dampers, though one than less then 'right' while it will all work, usually shortens crank life.

Edited by Moke Spider, 12 August 2017 - 09:54 PM.

[mini13]

good point, the assumtion I am making is the S damper is suited to engines similar to the S engine, ie reging upto around 7500 rpm, but that said the S crank differs substantialy from the std crank so god know what it is doing in terms of vibrations.... so hence my thinking of just stuff a viscous damper on and be done with it.

 

just for a bit of fun ive drawn up the overlap of all the large bore crank configs that sprang to mind.

 

 cranks.jpg   21.86K   21 downloads

Edited by mini13, 12 August 2017 - 10:12 PM.

[Spider]

It's likely that the Cooper S Damper would be better suited as far as factory dampers go, but that's only my best guess and nothing more.

 

Mind you, the wrong damper will make matters worse too.

 

Promised Graph - NOTE: This is NOT on a Mini Engine, I think it's an inline 6 cyl, I post it to show what a damper does

 

 

I'll have a look at your sketch,,,,

Edited by Moke Spider, 12 August 2017 - 11:00 PM.

[Spider]

mini13, your sketches really do show the differences quite well and it's clear looking at that, that once we get much beyond the stock 1275 stoke that harmonics are likely to be a real headache and some serious damper considerations / tuning is needed big time.

 

I recall Vizard mentioned someone (??) doing a 1275 that use Ford (??) Mains, that were 1/8" bigger in dia. I can't recall it all and I don't think he was on about harmonics in that instance, however, going down that route may help here with bigger strokes, the only thing is it will make the crank heavier, which does tend to lower the critical harmonic frequencies. Catch 22,,,,,