Briggs vanguard conversions

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

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  1. Jun 16, 2019 #521

    Hot Wings

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    :oops:o_O:(:mad::confused:?? More like my sacrifice for the year.
    Need to do a better job of keeping my posts on topic. :D

    The AV-36 plans restoration has top billing for my aviation related time so the B+S is going to have to be an as time allows project. But the AV-36 is actually another reason for doubling down on the engine conversion once the AV-36 plans are again marketable. A lot of the CAD work is going to be pretty routine so I'll have plenty of time to at least plan the Briggs conversion.
     
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  2. Jun 16, 2019 #522

    Vigilant1

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    This is a (propaganda) video (7:18 long)about the B&S Turf/Commercial 810cc engine. It was made some time ago (engine sticker still says 30 HP). Groovy animation, etc. Main points:
    - ZTR engines ride in the back of the mower in a cloud of dust and grass clippings, different from a lawn tractor. Lots of emphasis in this engine on keeping the dust out (this is of minimal importance to us, though reducing the air filtration gizmos may give us better performance).
    - The hydrostatic drives on ZTRs require high torque from the starter (even with a compression release, the starter is apparently still turning against considerable resistance when installed in these mowers). Impact on us: OEM starter may be overbuilt for our application. Perhaps, conected just to a prop, it will have enough torque to start the engine even if we remove the compression release hardware. That reduces weight, removes a possible failure point, and may reduce the chances of prop windmilling at typical glide speeds.
    - Ribs added to cylinder block (in the sump end) for increased rigidity under heavy loads.
    - Head fins include "cooling arches" to reduce head and esp valve guide temperatures. Gimmick? don't know. The Vanguard 810s have them, too.
    - Exhaust valve stems are hard plated and "ultra smooth"
    - Crankshaft journals/connecting rod journals are "super polished." (No mention of a forged crank or conrods in this video)

    All very understandable, I'm just joshing. The link you provided to all the wrist-pin oiling options really provides some avenues to be looked at (what's the 810cc engine got now, what can be easily incorporated).
     
  3. Jun 17, 2019 #523

    blane.c

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    All this information is adding up to it may just be easiest to invert the engines to provide lubrication to the piston and valve train parts not pressure lubricated. Provide a tube to the home built oil sump to provide pressure lube to those parts that already have it, and gravity feed oil to the sump. At least on the surface it is the least amount of internal modifications needed, just the oil pickup tube? Everything else is external modifications basically hole and tube work to get the oil in the sump.

    The Briggs dyno chart mentions the dyno testing is with gross power? 810CC POWER CHART.png
     
  4. Jun 17, 2019 #524

    blane.c

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    The engines may burn more oil this way, if the amount is acceptable just accommodate it with a larger volume sump.
     
  5. Jun 17, 2019 #525

    Vigilant1

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    I think inverting the engines has some advantages in some cases, but I can't see how lubrication is easier. The engine is designed to have a lot of oil spray/mist in the crankcase--that's how the cams/tappets get oiled, among a lot of other things. If we flip the engine over, what's the source of this spray? And where does the oil collect in the crankcase so we can slurp it up and send it to the alternate sump tank? The oil that goes into the cylinders has to be moved by the oil rings (as you point out, expect increased oil consumption) or go for a ride in the piston skirt (to the degree one side gets more oil, balance will be affected). As far as getting oil to the rockers and top end, we'd have to confirm that enough will enter each pushrod window and make it to the top--but because it is now the bottom, it will pool in the valve covers, not where we need it (on the rockers and valve stems, or exchanging heat with the top of the combustion chamber).
    Again I think there are some advantages to flipping the engine to heads down, but I don't know if ease of oil circulation is one of them. With the heads up, there's still a useable (but too small) sump at the bottom of the crankcase, and (I think) the existing approaches (dippers, etc) from the horizontal shaft engines can provide answers for the oiling challenges.

    Yep--without air filter or exhaust system.
     
  6. Jun 17, 2019 #526

    BBerson

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    I don't know if the sump is too small. Probably need to measure the sump bottom distance below the crank throw and compare that to a standard horizontal Briggs.
     
  7. Jun 17, 2019 #527

    BBerson

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    I checked the Honda manual and the horizontal and vertical have almost the same distance below crank. The vertical is a few millimeters more, actually.
     
  8. Jun 19, 2019 #528

    Hephaestus

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    FB_IMG_1560975190852.jpg Friend who's working on the prop adapter just sent me this and asked if this looked right. o_O:p:cool:
     
  9. Jun 19, 2019 #529

    pictsidhe

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    Redrive belt is awful thin.
     
  10. Jun 19, 2019 #530

    radfordc

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  11. Jun 19, 2019 #531

    Vigilant1

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  12. Jun 19, 2019 #532

    Hephaestus

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    I was going to say that looks like the Chinese clone they sell at princess Auto (like harbour freight) .

    The no warranty part says a lot to me. The good performance builders have a warranty, limitations yes, but not as is.
     
  13. Jun 20, 2019 #533

    blane.c

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    LOL
     
  14. Jun 20, 2019 #534

    akwrencher

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    That's for keeping the weeds mowed on the lake.....:D
     
  15. Jun 20, 2019 #535

    simflyer

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  16. Jun 21, 2019 #536

    rv7charlie

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    Vigilant's comments triggered a memory. There's a Gipsy Major powered Chipmunk in the back of a hangar on my field. When it was flying, the owner had to check the oil in its valve covers in something like 10 hour intervals.

    Now, back to your regularly scheduled programming....
     
  17. Jun 21, 2019 #537

    BBerson

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    Did it have a drip oil system? I think the early engines had open rockers. It would certainly be more air flow to the top of the head.
     
  18. Jun 21, 2019 #538

    rv7charlie

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  19. Jun 21, 2019 #539

    BBerson

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    So it's inverted. Strange oil system.
     
  20. Jun 21, 2019 #540

    rv7charlie

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    Yeah; the post about pointing the V-twin's cylinders down & worrying about oil supply to the valves is what made me think of it.

    It's certainly strange by our modern standards. But if you ever get a chance to fly a Chipmunk, you can forgive a *lot* of strange. :)
     

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