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Thread: Oil sump location

  1. #1
    Mike Switzer's Avatar
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    Oil sump location

    Using a converted auto engine (planning on a stroked 302 ford), in initial planning I was thinking I should go with a rear sump as you are more likely to be nose high than nose low. All of the larger capacity aluminum oil pans however are front sump, and front sump would actually fit better with the fuselage structure.

    So, using a 7 1/2qt sump does the location really matter? I have never had any oiling problem with a small block Ford in a car, and those are only with a 5qt sump.

    Also, I note that the sump on our O470 is pretty much flat from end to end. Any opinions?

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    Mike Switzer's Avatar
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    Anyone have any thoughts on this? Other advise I have gotten ranges from allowing for anywhere from 30 to 45 degrees nose up & down, if I do that I need a pretty deep mid sump pan.

    The sumps on production aircraft engines don't seem to be that deep - the O-470 is a little deeper in the rear (but not much) and according to the cutaways I have seen the pickup is in the middle. When I model it using Autocad 30 degrees up or down has the pickup sucking air one way or the other (either nose up or down) with a front or rear sump, depending on which end is higher.

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    Most automotive sumps have a shallow end to allow the engine to sit lower over frame members, suspension and such stuff. The deep end gives the oil pan the capacity to hold the correct amount of oil. Most airplane engines don't have the same restrictions so the oil pans can have a uniform depth. As long as you have the room you could have an oil pan made with a deeper section in the middle and modify the pickup to fit.

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    Mike Switzer's Avatar
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    Quote Originally Posted by mcmurphy View Post
    Most automotive sumps have a shallow end to allow the engine to sit lower over frame members, suspension and such stuff. The deep end gives the oil pan the capacity to hold the correct amount of oil. Most airplane engines don't have the same restrictions so the oil pans can have a uniform depth. As long as you have the room you could have an oil pan made with a deeper section in the middle and modify the pickup to fit.
    I'm thinking about that - I want the baffles & gates that are used in road race pans, but the Ford auto pans are almost all front sump & truck pans are rear. Kevco makes a flat bottom race sump & a flat pan for the Pantera that may work with some minor modification.

    And because I know someone will ask - yes the Pantera came with a 351 Cleveland. What do you do when you blow up your Cleveland and you cant find another? You install one of the new Windsor based 427 stroker motors.

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    Mike Switzer's Avatar
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    The reason this is an issue now is the landing gear fittings & the sump want to be occupying the same general location, so I need to find a suitable compromise.

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    I can not think of any O-470 powered airplanes that can maintain a 30 degree nose up angle long enough to lose oil pressure. And I do not know of any O-470 powered airplanes that are flown 30 degrees nose down long enough to lose oil pressure either. So you might want to re-evaluate your autocad analysis and perhaps look at the immersion of the oil sump pickup at say the critical angle of attack of the wing. That is likely the critical case.

    Flying acro you learn that momentary interruptions in the operation of the oil pickup do not result in loss of oil pressure. Its the longer interruptions, such as switching from upright to inverted and back, that show up on the gauge.

    Oil sumps are generally not structural, stressed lightly, and can be formed from light steel or even plastic. I understand that a number of cars use plastics these days. My tractor has an oil sump with a deep channel through it to allow a drive shaft to pass through. It has separate drain plugs for each side. So you can form a custom oil pan to meed your specs relatively easily if you like.

    Best of luck,

    Wes

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    Mike Switzer's Avatar
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    I was just using the O470 as an example since it is the largest aviation engine I have much experience with. I will be making more power in a lighter aircraft, so pitch up may be greater.

    I'm planning on stressing the structure for aerobatics, but I won't be doing any as I like to keep my lunch in my belly. (But if I ever sell plans someone else may want to, they can design their own oil system)

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    Lycoming oil pans are relatively flat also. I doubt that your power to weight ratio will allow you to sustain a higher pitch angle than a Pitts or an Edge. An estimate of your sustainable pitch angle can be calculated by combining your max angle of attack with your projected rate of climb at that AoA over distance. It is likely a smaller angle than you think, maybe 20 degrees max rather than 30, and maybe less than that.

    Best of luck,

    Wes
    N78PS

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    Mike Switzer's Avatar
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    The only place I found that made a pan close to what I want isn't returning emails or answering the phone, so I decided I will just make my own. Ordered a bare steel stock pan from Summit (along with some other engine accessories). I will perform surgery on it with the plasma cutter & torch.

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