Crank windage

[Jack Gifford]

Anybody here have experience running a Roots-type oil pump? Can someone direct me to an interior view of a centrifugal oil separator? I couldn't find anything on Dailey's website- other than an interesting video comparing scavenge-oil frothing with/without separator usage.

[Dynoroom]

I have run pumps with lobe scavenge in them Jack. No different in hook up or drive system, just more vacuum.

The best picture I have of a air-oil separator.

[Dynoroom]

A couple F1 dry sump pans & a new scavenge lobe design, Similar to current supercharger technology trends.

[maguromic]

That pan look similar to some recent cup pans I have seen. I wonder how they equalize the pressure between the cylinders?  Mike do you have a picture showing the inside of the pan?  Tony

[Rex Schimmer]

As I understand, to make these vacuum pumps work well they actually put a bleed orifice from atmosphere into the chamber that is being evacuated to allow a very small amount of air flow through the chamber. This flow prevents the vacuum pump from stalling which is a condition where it actually is not pumping anything and can lead to pump surge as air or combustion gases etc are leaked into the chamber and then the pump will evacuate them and then stall again, this can happen at fairly high cycle rate. At stall the power required to drive the pump drops as it is not doing any work. By adding a bleed orifice this is prevented and the vacuum level in the chamber is controlled.

Rex

[Koncretekid]

Rex,
Out of curiosity, I wonder if these bleed orifices have check valves to control the vacuum at which they bleed.  I'm thinking that if the orifice is too large and not controlled, the pump might just pull in air and not pump oil.  Analogy would be a two stroke motor with bad crank seals - - it won't start because the upstroke of the piston (vacuum pump) pulls in air thru the seals instead of fuel thru the carb.  At high RPM where the pump is more efficient, the opposite might happen and the orifice might not be sufficient to prevent "stalling."

I wonder how many hours/dollars went into getting that right!

Tom

[tauruck]

That motor looks like a V6 to me.

Irrelevant, but I'm just saying.

[johnneilson]

That motor looks like a V6 to me.

Irrelevant, but I'm just saying.

The oilsump housing pic looks like the old V10

[Jack Gifford]

... This volume deal also makes it sound like Jack Giffords block arrangement could be an interesting advantage compared to typical 4-cylinder engines...

... I agree. I considered blocking off the unused cylinders, but quickly decided that additional crankcase volume is preferable, if for no other reason than reducing the magnitude of pressure fluctuations in the crankcase...

I just discovered another advantage (having it on the engine stand in its eventual position made it more obvious): I won't need to include a kick-out on the oil pan, since the [empty] unused cylinder volume will serve that purpose quite nicely!

[Jack Gifford]

I'm c-r-e-e-p-i-n-g up on making a little progress toward the full-circle counterweight scheme. Having the new billet crank in-hand has allowed me to make cardboard mockups of the planned magnesium alloy filler segments, to more easily visualize machining operations (on segments and on crank counterweights). And I'm finally corresponding with the right person at Elektron for full specifications and material quotes of their Elektron-43 alloy- about 43ksi tensile strength, but pricey! The modulus-of-elasticity isn't as good as I had hoped, so I've got to get more precise with the deformation calculations.

[wobblywalrus]

Jack, how does the coefficient of expansion due to temperature change compare between the billet crank and counterweight materials?  Will just warming up cause the circular weights to get loose from the crank?

[Jack Gifford]

Thermal coefficient of expansion of Elektron-43 is 25.6 x 10^(-6). I still need to do all the engineering of the attachment scheme- might not be able to solve all aspects.

[wobblywalrus]

Jack, if thermal expansion becomes an issue consider titanium.  Its thermal expansion coefficient is less than iron or steel.  It will tighten up onto the crank when it gets hot.

[Jack Gifford]

... Thermal coefficient of expansion of Elektron-43 is 25.6 x 10^(-6)...

Oops! That seemed awfully high to me- about twice that of aluminum alloys. Looking back at the spec sheet, I now notice that number was per degree Kelvin, not Fahrenheit. So, per degree Fahrenheit it's more reasonable- about 14.2 x 10^(-6).

I also made an error converting gPA pressure units to KSI- so the elastic modulus isn't nearly as bad as I thought.

[At this rate, would you trust me to do any calculations?]

[Ron Gibson]

Sure. When I read stuff like that , my eyes glaze over.

Ron