Steps to scratch build a VW

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

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  1. Sep 1, 2019 #501

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    Yes and that is the reason the mineral oil T4 by shell is a solid choice. William is monitoring the supply for new shifts and if adding 1/2 bottle to every change you have a measure of protection should shell drop what we need. I think the VR1 is excluded from the policies and will remain viable ine can only hope
     
  2. Sep 1, 2019 #502

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    I keep my oil change interval short at 25 hours. Looks like clear honey until hour 20 and begins to darken but no sludge at 25 hours burning 100LL all the time about 2.5-3.5 gallons per hour depending on mission at hand.
     
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  3. Sep 1, 2019 #503

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    Don't forget the .040 orifice built into the plug that supplies oil to the #4 main bearing ( pulley end ). When using a flywheel drive aero engine, are you going to drill it out or leave it in ?

    With the extra oil to #4 bearing, when you drill the orifice out, there seems to be a little more chance of oil getting past the crankshaft oil slinger . So it seems to require a better low pressure in the crank case to stay dry around the prop hub when using the prop on that end.
    Has anyone tried an after market SAND SEAL pulley instead of the stock VW pulley for the flywheel drive engine ?
    https://www.cbperformance.com/product-p/1899.htm
     
    Last edited: Sep 1, 2019
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  4. Sep 1, 2019 #504

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    All the same for me. I try to burn 50/50 auto fuel and 100 LL most of the time.
     
  5. Sep 1, 2019 #505

    dmar836

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    I think the .040 orifice is a good discussion. I have often wondered about the "reversed" thrust loads on the #1 bearing with a flywheel drive conversion and it's effects.
    Dave
     
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  6. Sep 1, 2019 #506

    karmarepair

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    IF you install a sand seal, you'll need a new INLET for the crankcase, and the valve covers were the usual place to put a FILTERED inlet. https://www.jbugs.com/product/9164....MttKlt9mlPL_cg7-z_353uU6mOqsEggoaAio5EALw_wcB is the easy way to put a nostril in the valve covers, although this listing makes it seem like the seller thinks this is an OUTLET for crankcase emissions. Veeduber talks about this https://bobhooversblog.blogspot.com/2007/07/crankcase-ventilation.html and https://bobhooversblog.blogspot.com/2007/02/blow-by.html (one of his more long-winded pieces)
     
  7. Sep 1, 2019 #507

    karmarepair

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    The thrust bearing inside the engine needs to be set up differently when the engine is assembled.

    Every VW engine coupled to a manual transmission has to have the crank resist the thrust loads placed upon it by the clutch disk. This is USUALLY set between the main bearing and the flywheel with 3 shims, chosen to get the right clearance. This method works fine for Fan End hub Tractor applications, the usual practice for flying VWs. On a flywheel drive tractor application, the shims go INSIDE the case, with the INSIDE of the main bearing becoming the thrust face, reacting against the last crankshaft throw. The shim need their ID opened up a little to accommodate the fillet that SHOULD be there on the main bearing journal. I'm not sure if Bob ever posted this stuff to his blog, but attached are a few sketches.
    #1ThrustBrg.jpg ThrustShimsModified.jpg ThrustShimsHowToModify.jpg
     
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  8. Sep 1, 2019 #508

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    Flywheel drive VW engines were used in homebuilts in Europe in the 1950's. In 1960 I was thinking of starting to build a Jodel D-9. But got so discouraged about flying after having to start wearing glasses and had to forget my dreams of flying for the military or the airlines. I even decided to not build the D-9 and wouldn't go to an airport for about 9 years after being an airport bum since the end of WW-2.
    Latter I did finish a Falconar F-12 in 1979.
    http://users.lmi.net/~ryoung/Sonerai/Hugh_History.html
     
    Last edited: Sep 2, 2019
  9. Sep 2, 2019 #509

    karmarepair

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    Ha! That's my old web site.
    I think Bob Hoover (Veeduber) flew an Aeronca C-2 (C-3?) converted to use a VW engine (one of the ones <"36 HP"> with the cast-in generator towers - Bob got the engine for free from a local dealer when one of the early imports got rear-ended, and snapped the tower off the case) as early as 1955. The Jodel D.9 first flew in 1948, but I can't find when the first D.92, with a VW engine, first flew, but it had to be the early 1950's.
     
  10. Sep 2, 2019 #510

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    Small world. Hadn't thought about the Moon Maid in a long time.
     
  11. Sep 2, 2019 #511

    dmar836

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    Karmarepair, thanks for the info. So the pulling force of the tractor setup rides on the shims?
    Dave
     
  12. Sep 2, 2019 #512

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    In the stock set up the shims are on the flywheel side. given that there is only .003" end play I doubt it makes much difference what side the shims are on with regard to thrust. .003" divided up between 4 surfaces doesn't leave a lot of room for an oil film between the shims.

    I'd just turn the main bearing around* (move the dowel pin hole) and leave the shims on the outboard position - where they are easy to work with when setting the end play.

    * if the case thrust surface has been cut then this isn't an option. If this is the case then notching the back side of the bearing is the only option to make sure there is oil at the actual thrust surface.
     
  13. Sep 2, 2019 #513

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    When I built a cut case 1/2 VW I used a #1 bearing with the thrust surfaces in place of the #3 bearing. Enlarged the ID of the shims at the rear of the bearing and installed shims in front of the bearing. Had to turn down the rear face of the cam gear on the crankshaft to make room for the shims on the front side of the cam gear on the crankshaft. Also had to turn down the rear face of the large cam gear on the cam the same amount. The engine could be used at a tractor or pusher.
     
  14. Sep 2, 2019 #514

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    Same way I did my 1/2 VW - except I don't remember having to enlarge the ID of the thrust shims. Been a long time ago. I do remember cutting the gears.
     
  15. Sep 2, 2019 #515

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    Yes, have to enlarge the ID of the thrust shims a little due to the radius of the crankshaft. As in post #507.
     
  16. Sep 3, 2019 #516

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    It does seem strange to have the shims in thrust especially if they are not fixed and are “floating” about the radius of the #1 crank journal.
    Dave
     
  17. Sep 3, 2019 #517

    blane.c

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    So the shims slide down the crank journal?

    Annotation 2019-09-02 221250.png Are these commonly available? They are not likely to be thick, a few thousands?
    When you slide the crank "endo" in the case the big end of the rods have enough play and it doesn't matter if there is more clearance on one side of the rod than the other in the throw?
     
  18. Sep 3, 2019 #518

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    When using a shrunk fit or tapered prop hub on the pulley end of the engine , you also use a seal installed with JB Weld. ( VW Bus Rear wheel Seal ). IF you do not vent the crankcase in a low pressure area ( I do it how VW does it). I run the crankcase vent tube to the inlet of the carb, you will still have a little oil leak around the oil seal at the prop hub when nose down when you approach to land and at idle rpm.
    Blue hose in front of carb inlet in picture.
     

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  19. Sep 3, 2019 #519

    Charles_says

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    I've been using Shell Rotella T5 15W-40 in all my 4 stroke engines since about 2005. Wouldn't use anything else. (YMMV)

    Building a Corvair engine for flight use, I followed WW's guidelines.
    "ZDDP" is available at Eastwood.com Under 8 bucks.
    https://www.eastwood.com/ew-zddp-oil-additive-4-oz.html
     
  20. Sep 3, 2019 #520

    dmar836

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    Blane, In a car or pulley drive conversion the shims go on the flywheel end of the crank after it is installed and the case closed up. One must install shims and then the flywheel and torque it down with the “big nut”. This sets the end play of the crank. Measure fore/aft play with a dial indicator. This may take several attempts to get the right combo of shims.
    Not sure if your rod question is a separate one?
    Dave
     

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