Steps to scratch build a VW

Discussion in 'Hangar Flying' started by Little Scrapper, Aug 13, 2019.

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  1. Aug 22, 2019 #261

    Little Scrapper

    Little Scrapper

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    It hasn't been discussed yet, what if any prep work needs to be done for a flywheel side prop? Crankshaft or bearing considerations? I don't have any Wittman plans for the motor or extension so I'm not sure what he did to prep the motor itself.
     
  2. Aug 22, 2019 #262

    dmar836

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    Mine was half apart but had flown. There really isn’t anything done to the block that I can see. There is a notch or two cut rather crudely into the cone flange on mine but I imagine that was due to the individual builder and I’d doesn’t have matching notches in the block flange.
    “I see nothing... nothing”

    Dave
     
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  3. Aug 22, 2019 #263

    Little Scrapper

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    I think when I get back from vacation next week I'm gonna start on the engine. I still can't decide on which end. Doing it Steve's way is probably best.
     
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  4. Aug 22, 2019 #264

    dmar836

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    I need to order those cone end plans to see if they jibe with the drawing I have. I'm all for going the other way around and would do it if it wouldn't jack up the design. I might have to find a still of the V-Witt Ed acknowledged that showed up but never raced. My guess is it might not have passed tech based on the nose appearance alone! I think he either had a corvair or the VW turned around. Someone mentioned it once but I can't remember what they said!
    Dave
     
  5. Aug 22, 2019 #265

    dmar836

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    In the video the rest of the plane appears to be built nicely but that nose just doesn’t look right! That n-number is a Citation now so... 0D887D2C-092C-4540-8716-B05FE86362AF.jpeg
     
  6. Aug 22, 2019 #266

    lakeracer69

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    Oil related questions. Oil filter, no oil filter, oil cooler or no oil cooler, or both? I have read pros and cons both ways. Also, what oil weight and type is used predominately. Shell Rotella looks like a decent choice in that it still has some zinc in it. I have seen that some change the oil every 25 hours when they adjust the valves.

    I also remember reading that Pops runs a SCAT hose from the nose bowl area, that blows air on the finned oil sump, to help keep things cool.
     
  7. Aug 22, 2019 #267

    Hot Wings

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    For me, both would be required. Even if you change oil at 25 hours (=to about 2000 ground miles) the filter still helps. With the HVX mods there is more oil flowing past the hot heads. That heat needs to go somewhere and oil has an accelerated, non linear, break down rate as temps increase.

    All of my personal VWs had oil filters. Usually mounted on the left transmission tongue. Easy and clean to change at service time.
     
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  8. Aug 22, 2019 #268

    Pops

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  9. Aug 22, 2019 #269

    dmar836

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    What’s TBO for one with and one without?
     
  10. Aug 22, 2019 #270

    Pops

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    Yes both. Buy good quality filters. I had a defective oil filter and on start up the oil filter was not crimped correctly at the top and it burst. Had the high oil pressure control valve at the flywheel end set at 57 lbs. Made adjustable with ----


    https://vwparts.aircooled.net/Oil-Pressure-Adjuster-Kit-p/oil-pressure-adj-kit.htm
     
  11. Aug 22, 2019 #271

    Hot Wings

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    My SWAGuess is that they would both be = about the same. The rear drive however would use off the shelf VW parts and not need a modified crank/prop hub/bearing. The rear drive parts, other than the bearing, should not need any service other than cleaning and inspection.
     
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  12. Aug 22, 2019 #272

    Pops

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    And you can do a Major Overhaul of a VW engine for about $500 of parts and a little work.
    Price a Lyc exhaust valve.
     
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  13. Aug 22, 2019 #273

    blane.c

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    I vote prop it on the flywheel side. As if that "cone" is an overwhelming problem for you, "pssst". And that will eliminate concerns of force one prop hub cause' ya' won't need one.
     
  14. Aug 22, 2019 #274

    Vigilant1

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    In a post here, fly2kads gives a current draw of about 4-5 amps for an electronic ignition on a 4 cyl engine. If that holds, then a 7 AH battery would give about an hour or so of flight (if also driving a tablet, etc).

    And then, there was the more experimental proposal Pops had of using thermoelectric generator chips. No moving parts, no power draw from the engine, not too pricey. But, Steve Wittman didn't do it that way, so . . .
     
  15. Aug 22, 2019 #275

    Vigilant1

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    Like Steve Bennett wrote: What's the TBO on your car engine or lawnmower? It needs it when it needs it.
    I'm sure an oil filter helps keep the oil cleaner, it's just a tradeoff with a bit more weight, an additional thing to go wrong, and possibly reduced oil flow. IIRC, they do make a nice, well-made permanent filter housing with replaceable elements, that would probably reduce the chances of a blowout (which has been a problem experienced by some Sonex flyers, too).
     
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  16. Aug 22, 2019 #276

    blane.c

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    With a prop extension like that I would spend a little extra money and time on the balancing. Static and then rotating balance on cone/flywheel setup independent of rest of engine, properly balance engine prior to assembly and then, followed by having the prop dynamically balanced when the whole assembly is bolted together and running.
     
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  17. Aug 22, 2019 #277

    Vigilant1

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    I can see that cone fabrication/bearing mount/shaft alignment and fitting to the engine as taking about twice as long as the engine build. Handy folks (not me) routinely get their engine finished in one day in the shop.
     
  18. Aug 22, 2019 #278

    blane.c

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    I am wondering why not build a simple bench test for oil filter cans? Before putting them on airplane test them to X psi on the bench. Not so much psi as to ruin a good can but enough to insure it is a good one.
     
  19. Aug 22, 2019 #279

    blane.c

    blane.c

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    I don't. It is pretty straight forward. Sure some time but not as much as a proper engine build. Measuring all the clearances, deck heights, cc-ing chambers, proper push rod lengths, balancing parts etc. no way.
     
  20. Aug 22, 2019 #280

    blane.c

    blane.c

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    When I was in A&P school back in the mid 70's the instructor made us tear down the hydraulic lifters and measure all the pieces for clearance.
     

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