1/4 scale Porsche 917 180 degree V12 Build

[crueby]

Ouch!  Glad you are back to some play time!

[Admiral_dk]

Man - that is a hard program .... you certainly earned som R&R - so enjoy 

Per

[Roger B]

Glad your back on model making    but I know from my friends in Dracut that good people are almost impossible to find at the moment   

[steamer]

Some motivation....

<a href="https://www.youtube.com/watch?v=XpcTAL6Ogqk" target="_blank">http://www.youtube.com/watch?v=XpcTAL6Ogqk</a>

[steamer]

Productive 2 days!

The pump is together, and I've ran it in a test stand at 4000 rpm for an hour....see video of the set up

It pumps approximately ( by estimate only....I've not measured it yet)  .8 liters a minute at 4000 rpm.    All seems good!

https://www.youtube.com/shorts/iLhpYt9hjyU

[steamer]

The gear pump calculations to estimate flow.

Pressure has not been measured, but I can't stop the flow with my finger.....so enough to flow through the engine.

Dave

[Kim]

Great little pump, Dave!  It really seems to be moving the water! 

Kim

[steamer]

Great little pump, Dave!  It really seems to be moving the water! 

Kim

Thanks Kim!

Actually low viscosity oil.    Pumps really well!

Dave

[Vixen]

 

Mike

[steamer]

I didn't see anything that even remotely looked like cavitation.    I saw some air in the oil pump side under operation, but the inlet is so close to the surface of the oil I think it was just drawing in air.    Regardless....4000 rpm is considered maximum   ( 8000 rpm engine speed) and it ran like a little watch with no issue for an hour..   I'd like to measure the flow, and hopefully the pressure available, but I think I can live with the gearing as is.   That was the last unknown for the internals of the engine block.   So I can finalize the engine block and get it machined!

Dave

[crueby]

Excellent!   Looking forward to seeing how the block is done.   

[Admiral_dk]

Great test result Dave 

I must admit to ignorance in regard to how much pressure is needed in any Smooth Preasure Bearing ....
But considering that you don't plan to run it with a load - I will be very surpriced if this isn't far beyond requirements 

Per

[steamer]

Great test result Dave 

I must admit to ignorance in regard to how much pressure is needed in any Smooth Preasure Bearing ....
But considering that you don't plan to run it with a load - I will be very surpriced if this isn't far beyond requirements 

Per

The outlet port is .09"   or just over 2mm......when I close it off with my finger , I can't stop the flow....so at least 10PSI.....probably much more....that said, as I'll be running splash or more accurately a spray bar aimed at the big ends of the conrods....I think that most of it will be diverted back to to the oil tank.     10 psi is all the pressure I need to make a spray bar work great...

Dave

[petertha]

Dave, your oil pump assembly is a work of art! If I go too deep in the weeds with my newbie questions, just let me know. I don't want to detract the build post. Maybe offline is better.

- I looked at your spreadsheet just a bit. Some input parameters look vaguely familiar to articles I've downloaded but never managed to piece together much of anything even as a rough sizing tool. I pretty much had given up & started looking over other model pumps to plagiarize & cross my fingers. Yours is MUCH more detailed. Can you elaborate on how you put this together? Have you been down this design path before on other model engineering projects or was it this particular (Porsche) task that triggered its development?

- Am I correct in assuming the Lubrication & Scavenge pump design formulas are identical (from your spreadsheet) but W (gear width) is different to yield different flow rates & pressures? Lubrication = 0.56 l/m @ 10 psi vs Scavenge = 0.87 l/m. at 5 psi Is there some kind of rule of thumb that says scavenge should be +50% more or something?

- I suspect the annular gap between gear OD & housing cavity ID is tied up between the L&D terms, but can you give me a ballpark figure of what your annular gap measures?

- I'm told that this 'intersection area' where the gears come together & depart is quite important. Would you agree? Maybe I missed but I didn't see any dimensional reference to its shape & its not really shown on the inset sketch. Can you elaborate?

- When you calculate torque & power, are you looking at this as some percent of engine output power, kind of like a necessary parasitic cost of lubricating because they are mechanically driven?

My radial engine is premix oil in nitromethane, so essentially mist lubrication. I might be pushing the limits of what that accomplishes, so I told myself 'next' engine will have oil pumping system. I wanted to take some baby steps & build a mockup test pump similar to your test bath apparatus. Gear cutting anything that small I suspect is above my pay grade so was looking at thinning commercial spur gears. Should I expect some lower performance vs. 'designed' gear lobe profiles. Would I be looking at 'true-ing' or lapping the gear OD to make them suitable for pump gears?

[steamer]

Becoming more plausible every day!