Sludge trap

[Colsbeeza]

On a related subject,
Has anyone measured the density of the typical crud removed from the sludge trap.? You know - weight and volume of the dry crud. Otherwise anyone hazard a guess.?? Or the typical mixture of metal, atmospheric dust (silica and alumina?), carbon (carbon black may be similar?) Hardened oil,? Just ballpark numbers would do.
I had my crank balanced many years ago before the internet and this Forum, when I also had no idea what 70% meant. I recently checked the receipt, and it does say 70% BF. That number sounded good at the time.
After enquiring whether the workshop had removed it for cleaning, "No we blew it out with compressed air". So I removed and cleaned it. It was more than half full.  It had clearly been blown out with compressed air, but the remaining crud was dry and hard, having been idle for some 15 or so years.
On calculating my balance factor yesterday (with clean sludge trap), I got a BF of 55.4 using same pistons, rings, rods, gudgeons & circlips.
I think there was sufficient crud in the trap to explain the difference. My spreadsheet suggested that about 80 grams would explain it. I measured 30 mls capacity of the sludge trap, but the density or SG of the crud would be helpful in making sure I am on the money. It will be much higher than the SG of oil no doubt.
On the positive side, the bike has done 80 miles since re-commissioning, and had been running smoothly up to about 60mph, so I am relieved that it wasn't cleaned first before balancing. My new pistons are lighter, so calculate a new BF of about 58.7, which is about where I think I want it.?
Hopefully I will be well-armed to talk to my new engineering shop about what to do.
Cheers
Col

[muskrat]

G'day col.
That's a question for a mastermind (certainly not me). SG of water is 1 so 30ml = 30g. If the trap was 1/2 full = 15g. Now the SG of the sludge would be 15g if it was water. SG of oil is 0.9, aluminum is 2.5, carbon is 2.1, cast iron is 7. So saying 25% of each would give a SG of 3.125 x 15 = 46.87g.
Std is 54% or there abouts and 65% for racing. At 70% it would walk out the door backwards if on the c/stand at anything over idle DAMHIK.
Cheers

[Swarfcut]

   I suppose to be absolutely accurate, the crank should have the oilways full of oil when measurements and comparisons are being made, but in any event  the balance factor is related to the rotational speed. In other words there  will always be a sweet spot, with the least vibration and mechanical clamour and the position of this on the speed range will vary with the balance factor used.

   Also in theory the sweet spot will change over time,  as the sludge accumulates and the balance factor changes. It also changes as the pistons carbon up, but whether these changes are important is subjective, your rough old dog may be considered a smooth ride by someone worse off. In fact depending what you start with, it may smooth out or roughen up at your favourite riding speed.

 As for the composition of the sludge, a few varied samples and access to your local neighbourhood  Spectrophotometer and Gas Liquid Chromatograph will sort that one out.

 Swarfy.

[BSA_54A10]

It is the dynamic balance that is important, not the static
And yes everything has to be taken into account right down to things like the center punches in the sludge plugs, and of course the actual sludge plug.
A hex one is substantially lighter than a standard slotted one.
However as you are not building a Daytona racer I would not get too upset about it

[muskrat]

G'day Swarfy.
I agree about sweet spots but trying to keep it clean. 
My A7 racer was smooth as silk at 6000rpm and up. I think it was up around the 72% mark. But at that speed I was more concerned with getting around the corner
Cheers

[muskrat]

G'day Trevor.
Some of us don't have access to dynamic balancers ( I lived 8 miles from 240v power). Mine was static with the oil galleries filled with 25w oil and plugged with wax.
Under 4 grand it'd shake my tooth fillings out.
Cheers

[Colsbeeza]

Thanks Fellas,
Musky, I also did similar guessing at the components in sludge. Bit too hard, as most of the components would have reacted with each other over the years and formed What knows.??
It is so smooth up to 60mph that there is no doubt the actual BF is quite low.
Anyway, I am getting it dynamically balanced, so hopefully I will end up with BF somewhat less than 75%. He He.
Col