Edwards radial 5 lubrication

[petertha]

I was looking over the plans & wondering... Can anyone with building experience of this engine comment if I'm understanding the lubrication system correctly. The recommended fuel is methanol with 3-5% nitromethane. The oil is castor. But unlike typical RC engines, oil is not pre-mixed in fuel, it has a separate circulation system.

I've scribbled on top of plans only to help illustrate with questions. Is this the gist of it?
- fresh castor oil from reserve tank feeds a pump
- pump gets activated by an eccentric cam on a plunger
- pump feeds into the top of the crankcase nipple & sprays on moving internals (crankshaft, master rod assembly etc.)
- and (I think) also feeds into area of cam gears, bearings & related front side internals via a separate passage?
- waste oil drains by gravity into sump, filter screen in there
- pump depletes oil sump on separate circuit

Questions

- I noticed what I think are vent holes in the crankcase (to atmosphere). I guess this is a requirement for this kind of lubrication system?

- Plans say a 4 oz tank. Is this acting as a reservoir and also positioned to keeping head on the pump all the time?

- I don't quite get the pumping action ball bearings & O-rings & cross holes in the pump body. Is it kind of a check-valve thing? (pressure moves balls against a spring, oil flows, balls return to close circuit).

 

[mu38&Bg#]

I don't have The drawings for this engine, but from what I see in the prints everything you are thinking sounds correct. I have my doubts that much, if any, oil gets through the long and narrow passage to the front, but if they are out there and running it can't be much of a problem.

Do you have any concerns specifically?

Greg

 

[petertha]

Hi Greg. Just in case you were ever interested, the Edwards plans are still available for download from the File section of yahoo groups (R_and_R engines group name).
http://groups.yahoo.com/group/R_and_R_engines/files/

No specific concerns. I'm just picking up again on my own radial design again & come up with a few better options since this post
http://www.homemodelenginemachinist.com/f26/radial-engine-carb-position-17308/

The induction still comes in from the rear to the backside of the crankcase. The idea is that fresh fuel/oil mix contacts the cams & gears for lubrication & this volume acts kind of like a big intake manifold feeding the intake tubes. But so far I've kept the front side crankcase as a segregated chamber mostly thinking piston movement pulses might mess up induction. Actually the rear bearing is somewhat open, so its not really sealed as such.

But now I'm wondering if enough oil will migrate down from the cylinders in the front portion to sufficiently feed the front & rear bearings to keep them happy. I know in my typical RC engine dismantlement, there is always a nice little oil puddle in there & this engine has 4 more cylinders. And I know one fellow has built & runs the 1/6 scale SIC plans Kinner JZ5 (glow) in a similar fashion.

Anyway, that's what got me looking at the Edwards. I never really paid attention to the pump before. Its quite neat. AFAIK, its the only methanol/glow type engine that does not premix oil in fuel, rather it pumps oil over the mechanical goodies & recirculates.

 

[mu38&Bg#]

I lost a post because I thought I was logged in. The cliff notes.

Kavan FK-50 used sump oil, with 2% oil in fuel.

The Edwards needs proper oil distribution to divide oil flow. The short and large manifold to the crankcase will flow virtually all the oil as there is very little pressure to push oil down the long and small branch line. The simple fix is using the same .041" orifice on the feed to the crankcase to roughly equalize the flow.

The Evolution brand radials pull fresh charge into the crankcase then to the cylinders. This works well because it brings in fresh oil and removes blow-by mess. A guy in France offers a conversion kit for the OS FR5-300 radial to take advantage of this concept.

Greg

 

[mu38&Bg#]

I forgot. What kind of pressure pulses are you expecting in the crankcase of a radial, there are none. Because pistons are on a common crankpin there is no variation in volume.

I read the other thread and had these comments. Regarding the intake flow, the reality is the flow will be from the carb to the plenum, plenum to the intake. Each intake action is drawing from the entire cam box volume. It's not as bad as you think. Venturi dia = K x (Displacment x kRPM/2)^.5 K= .65 to .8 and is essentially a factor for volumetric efficiency. The division by 2 accounts for it being a four stroke engine. I'd start with a carb at the low end of the sizes. With methanol fuel you can increase venturi area by 20%. I don't know what kind of power these engines make, but specific power would give a good indication of actual air consumption.

Greg

 

[petertha]

Because pistons are on a common crankpin there is no variation in volume.

I see what you are saying now. The front chamber, even though pistons are coming up & down & rods thrashing about, it remains the same overall volume. Pressure buildup from a downward piston is being equally absorbed by the other upward moving pistons, net result zero. So kind of a stagnant chamber with static ~atmospheric pressure.

..the reality is the flow will be from the carb to the plenum, plenum to the intake. Each intake action is drawing from the entire cam box volume. It's not as bad as you think.

Thats what I'm hoping to hear. When any one intake valve opens, it draws reduced pressure on the plenum & starts sucking charge as fresh atomized induction comes into the plenum from the carb. But meanwhile the mist deposits some oil film layer (premix fuel) on the cams & gears inside the plenum.

I'll update with some new drawing sections when they are done & let you have a looksee. Im feeling better about this now.