36 replies to this topic

[Blatherskite]

More of a interest point rather than assistance to nick.... 
 
from what i recall the swiftune race engines ( dc5 crank or whatever) were recently running NIL damper..... ( ie none) again i thought i had seen that previously most of their built engines sported the KAD heavy ones but Swiftune were thinking of developing their own and so at last years mid ohio races - the car piloted by nick swift went damperless...... again no one suggested this was the answer for hi revs,,,more of a state of not sure what to fit
 
the romac and med ones both seem good in use with standard type cranks  with a couple of med ones ( a year or so ago now, being too tight a fit without a tiny linish)..... although longevity is the question for racers.... it seems the elastmer/rubber/or plate don't last a lifetime, but we would hope for a few seasons
 
the mechanical you beaut ones produced by ATI - (nascar engines running them)would be wonderful if designed for our little motors but alas no volume no investment/return..... 

 
If the crank does not have a resonance that coincides with engine's power band then you should be able to run without a damper. The problems happen when they coincide.
 
I am curious to know if anyone knows of 1275 engine dyno tests taken on identical engine with/without crank damper, I will post this as a separate thread.

Is there any way, without spending huge amounts of money, to check the vibrations and maybe get the right crank damper for the engine?

Edited by Blatherskite, 20 April 2015 - 05:37 PM.

[nicklouse]

Thanks Nick.

Ok here is a picture of the rear of my damper. A standard one here you ca easily see the rubber joint. When you look at the front you just see a grove.

[spiguy]

Thanks for that Nick. I'll need to have a look at mine. Should have the radiator out soon anyway to change the engine mount.

[Earwax]

to blatherskite

 

the short answer is no.  But that is exactly what damper makers do, they run the engine, '''feel the vibration frequencies) and then design the damper to suit... 

there are lots of differing thoughts on fluid types, mechanical types, set frequency vs all frequency ones....but i haven't seen any data as such for minis in general ..this is the stuff carbon was trying to find.... It is no good fitting any old damper if the harmonics and the dampening don't align..... and i would be interested to see the variation when for instance someone lightens the bottom end.... which way does the harmonics frequency slip?   the original S one seems to be pretty good... It is kinda funny, i wouldn't run a 1275 without one, but i haven't anything more than anecdotal evidence that the ones i run are good for the job...,,, maybe it is like red stripes making us go faster, but i think the science is better for the dampers though.   

 

Regarding cracking of cranks, in different cars motors ( with different harmonics zones) there are stories of not changing gears at certain revs or watching how you back off at the end of the straight, as it is thought the harmonics stresses the crank but the sudden acceleration/deceleration does the damage????? again would love to hear from more knowledgeable people

[nicklouse]

General consensus is the lighter the rotational parts the higher the frequency that needs the damping becomes. So therefore the damper should/could be smaller as it has less work to do.

But I have forgotten most of that do am very happy to be corrected.

But that damper above has seen about 9k and over 8k often even though I am always expecting something in the engine to let go.

Never bothered with the S ones as people always were asking too much for them back then.

I will be rebuilding (assembling) with the same damper for now as I am not ready for the mappable ignition just yet.

I wonder when the woodruff key split as there has never been any clue that it had.

[nicklouse]

First time I've seen two parts share a woodruff key. IMHO each should have it's own woodruff key.  Damper side of machined groove looks damaged. Any new damper would probably do the same thing even if secured with a new key.  Maybe a good machinist could machine a new groove in situ?

Not worked on Minis long have you. Welcome to the '40s. 1940s.

[tsumini]

 

First time I've seen two parts share a woodruff key. IMHO each should have it's own woodruff key.  Damper side of machined groove looks damaged. Any new damper would probably do the same thing even if secured with a new key.  Maybe a good machinist could machine a new groove in situ?

Not worked on Minis long have you. Welcome to the '40s. 1940s.

 

No haven't worked long on minis. Missed the '40s too.