Briggs vanguard conversions

Discussion in 'Firewall Forward / Props / Fuel system' started by Hephaestus, May 12, 2019.

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  1. Sep 28, 2019 #981

    Vigilant1

    Vigilant1

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    A bit of back-of-the-envelope calculation regarding over-the-cowl sightlines.
    - My diagram of the B&S 810cc engine (attached) differs a bit from the measurements on the drawing by Hephaestus. By my measurement using a bright light and squinting old eyes, vertical distance from the crankshaft centerline to the topmost edge of the valve cover is 10.4". If we compare that to the given "down" (crankshaft centerline to bottom of case) distance (5.88"), then it looks like, if we keep the same prop location, the top of the cowl could be 4.5" lower if we flipped the engine to be heads-down (BTW, it looks like TiPi has taken the other approach and will keep the top of the cowling at about the same location and will use the extra clearance to bring the prop (and thrust line) higher by several inches).

    If the top of the cowl is 4.5" lower, and the pilot's eyes are 60" horizontally from that high point in the cowl, the improved downward FOV equals 4.3 degrees. To get an idea if that is significant--it's about 2" down at arm's length. Also, the 4.5" increased height for "heads-up" orientation is a the top of the bumps for the cylinder heads, the SD-1 cowlings dip down between the heads to provide a bit better visibility directly on front of the nose and to streamline things a bit (a large spinner also helps, as does their prop extension).

    Prop clearance/ length/performance: For direct drive at 3600RPM and 30 HP, it looks like a 42" prop is all that is needed, at least from 70-120 MPH ( a longer prop might be useful at lower speeds, esp to reduce takeoff roll).

    Optimized for 70 MPH (approx climb)
    40" dia: 62% prop efficiency, 100 lbs thrust
    42" dia: 66.2% prop efficiency, 106 lbs thrust
    44" dia: 66.6% prop efficiency, 107 lbs thrust

    Optimized for 120 MPH
    38" dia: 79.4% eff, 74 lbs thrust
    40" dia: 80.2% eff, 75 lbs thrust
    42" dia: 80.9% eff, 76 lbs thrust
    44" dia: 80.9% eff, 76 lbs thrust
     

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    Last edited: Sep 28, 2019
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  2. Sep 28, 2019 #982

    Vigilant1

    Vigilant1

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    That wasn't very considerate of them. :) Hmm- I guess I'd risk excommunication from HBA if I suggested giving that part of the case a good scuffing-up, put a pipe nipple where you'd like it, and then fill the area with JB Weld? Too hillbilly?
    Well, these engines are flying, so someone has found a way to get the oil in there.
     
  3. Sep 28, 2019 #983

    Hot Wings

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    Last edited: Sep 28, 2019
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  4. Sep 28, 2019 #984

    Vigilant1

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    To my eye, that inverted direct drive setup looks about perfect for a Quickie.
    I suspected your scale might be wrong, the engine looked so small compared to your pilot. But the measurements don't lie--these engines are just small.
    Edited to add: I just saw the upright direct-drive model. That looks great, too. It doesn't look like downward visibility over the heads would be a significant issue--approx 12 degrees below the horizon over the nose. I'm sure that's better than any C-152 I ever flew.
     
    Last edited: Sep 28, 2019
  5. Sep 28, 2019 #985

    Hot Wings

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    Edited the pics some. Still getting up to speed on the new software.

    Yes, the scale is correct. The "dude" is 6' 2"
     
  6. Sep 28, 2019 #986

    Hephaestus

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    Somewhat the point I was making with the spinner comment. It's only 18" tall with the stupid air-cleaner that none of us will use.

    [​IMG]

    Looking at that I have to wonder how much fun cooling will be...
     
  7. Sep 28, 2019 #987

    Hot Wings

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    If you actually do it this way you will have the same kind mof cooling problems the Quickie did with the original Onan. Both the Onan and the B+S are designed to have cooling air come from the non PTO side, or the side next to the firewall. It's not an insurmountable problem.

    Links to a couple of 3D PDF files so you can look at the B+S engine from any angle - section views too. Too large for HBA.

    https://www.dropbox.com/s/tpzv01tv22t2fwf/upright.PDF?dl=0

    https://www.dropbox.com/s/zn9mopw6iz9xv56/redux.PDF?dl=0
     
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  8. Sep 28, 2019 #988

    Vigilant1

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    I would have thought that giving the hot side of the heads the first shot at the incoming cooling air would be better/easier than trying to cool the exhaust area hiding on the back side of the head, requiring that the (already heated) airflow be turned around a corner to reach them. What problems did the Onan's have with the exhaust ports in front? Thanks.
     
  9. Sep 28, 2019 #989

    blane.c

    blane.c

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    Looking at your post #932 this thread of the outside cover removed picture and the picture this post, I fail to see were the oil is supplied to the pump? Is it supplied at/around the pressure relief valve? And slot? What slot? There is a groove in the main bearing housing I assume is for thrust bearing/shim oil?

    And Hot Wings post #939 this thread is that a different case than we can expect to see for a newer model of the 810cc?

    Maybe the 810cc needs its own thread?
     
  10. Sep 28, 2019 #990

    blane.c

    blane.c

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    My apologies, I think I see the slot now at the base of the oil pump tower. There is a "bump" on the other side of the housing. Does oil come in the slot go thru the gerotor and go into the "bump" were it can go to the oil filter gallery or out the pressure relief valve?

    Perhaps fitting and sealing a flat plate over the slot, the plate could have an easier to attach something to fitting in/on it?
     
  11. Sep 28, 2019 #991

    pictsidhe

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    The slot is just off the end of the governer shaft in the fist pic. It is below it in the second pic. My one has the slot under the screen on the left. Hard to see.

    Interesting that they ditched the screen. That should increase replacement engine sales! It will be much more of a pain to attach a feed pipe to. I'm thinking a plate and epoxy putty to match the shape and screw it all together. Ugly, but should work. I'd probably do a flat surface adaptor puttied and screwed on, then bolt a removeable feed pipe on top.
     
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  12. Sep 28, 2019 #992

    pictsidhe

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    The pressure relief valve is visible in my pic without the rotors in place, It is between the in an out ports. There is a plug holding the spring in which looks pressed in. That will be fun to remove.
     
  13. Sep 28, 2019 #993

    blane.c

    blane.c

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    Could the "slot" be blocked over entirely and feed oil in from the cover side (new supply hole)?
     
  14. Sep 28, 2019 #994

    blane.c

    blane.c

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    Grease? Block off other avenues of escape and use grease gun to put pressure on it. Should pop out like a toaster strudel.
     
  15. Sep 28, 2019 #995

    pictsidhe

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    Yes. Along with a drop in port plate with correct out port and a new recessed cover with correct in port, that would work.
    I'd rather keep the pickup pipe inside, myself.
     
  16. Sep 28, 2019 #996

    pictsidhe

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    That could work in production. It would be harder on the new slotted ones. The plug and spring are on the inlet side, so the pump and intake ports would need blocking. They are large diameter so there would be a lot of force on them. I'll likely drill and tap it and pull it out.
    There was a piece of Al swarf under the cover plate o-ring on mine. No effect on the seal, but I think I'd like to completely strip a new engine before putting it in a plane.
     
  17. Sep 28, 2019 #997

    blane.c

    blane.c

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    Yes. The oil level doesn't need to be that high with the pickup tube sealed. And using BBerson's suggestion #969 of a "p" trap to keep a wee bit of oil to aid suction?
     
  18. Sep 28, 2019 #998

    Vigilant1

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    Yea!! "Ugly but works". Is there enough meat in the case there to mill a flat-bottomed round cylinder into the case so it encompasses the crease/inlet, then tap that hole for a new oil fitting?

    As far as the reason for the redesign--maybe to make the very last drops of oil fully accessible? Running out of oil is a major cause of mortality in these engines.
     
  19. Sep 28, 2019 #999

    Hot Wings

    Hot Wings

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    It could, but even that is not a simple operation with the slotted pickup. I don't have mine apart at the moment for pictures. Mine had a little square screen slipped into the slot. It may still be in my disposal parts box.

    The oil pressure relief piston could also be made external, and may have some merit especially if the pump volume is doubled. Again, IIRC, the stock pressure relief just shuttles oil from the out port of the pump back to the in port. I'd like to see the pressure bled off down stream of the pump so if it fails open there is at least some oil going past the bearings.
    +++++++
    Regarding the backward air flow for cooling:

    The stock head is designed to get it's air from the center of the "V" over the top of the spark plug. From this point of view it doesn't matter much if the air starts from the exhaust/PTO side or the intake/flywheel side. But once past the valve guides the only option is to exhaust the warmed air out the tunnel under the rocker arms. This tunnel faces the exhaust/PTO side. So somewhere in the system the air will have to do a 180 if the PTO side is forward.

    Reversing the flow through the tunnel under the rockers and then out the center really isn't an option because the volume past the valve guides into the "V" is a very divergent and messy path for the air. It is also the only place there are any cooling fins. There are no fins in the tunnel under the rocker arms.

    I may get some pics later today, but it's time to winterize the yard and house. First snow expected Monday.
     
  20. Sep 28, 2019 #1000

    pictsidhe

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    Jeez, it was 90s here yesterday.
     

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