Steps to scratch build a VW

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

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  1. Aug 23, 2019 #301

    dmar836

    dmar836

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    Mount for mag on pulley end of case.

    upload_2019-8-23_12-32-36.jpeg

    upload_2019-8-23_12-32-58.jpeg

    upload_2019-8-23_12-33-17.jpeg
     

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  2. Aug 23, 2019 #302

    fly2kads

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    That mag mount is pretty interesting! It looks like there are just two bolts holding the assembly to the case? I wonder how well it keeps the mag in alignment? Also, it looks like you would have to take off the mag to service the oil pump? Fortunately, that isn't something you have to do often.
     
  3. Aug 23, 2019 #303

    dmar836

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    I really don't know how well it worked. There was a third point of support with that strap seen going up. I can't remember where it went - maybe to the head.
    Dave
     
    Last edited: Aug 24, 2019
  4. Aug 23, 2019 #304

    Vigilant1

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    On the subject of pumping a >lot< of oil through the heads to remove heat: Here's the two-stage oil pump for VW's that I'd seen before.
    https://vwparts.aircooled.net/CB-Performance-4-Gear-Dry-Sump-Oil-Pump-CB1745-p/cb1745.htm
    It is designed with one set of 26mm gears that serve as a high-volume scavenge pump to remove oil from the case (making it dry sump) and pump it to a remote tank. A separate stage with 21mm gears is the pressure pump for the engine. But, for heat removal from the heads, I'm suggesting the 26mm stage could be used to remove oil from the regular sump in the case and circulate it through a spray bar in each head, it could flow back by gravity and then to the 21mm side of the pump which would supply high-pressure lube to the engine (as normal). If both pumps draw from the sump, put the 26mm pickup higher so the 21mm pump is never starved for oil.
    Here's a video of how a guy modified it to change the functions of the 21mm and 26mm stages by adding a stock full-flow cover and plugging an internal passage. So, this pump could be modified many ways to make two independent circuits (e.g. 26mm side supplying the engine lube, 21mm side supplying the head cooling circuit", etc)

    There are lots of variations on this theme (incl best placement for the oil cooler, maybe make a dry sump, etc).

    Use of oil to keep the heads cooler is probably complicated overkill for a regular VW aero engine making 60 HP or less, but at the 70+ HP level it might be useful to keep head temps within the desired range. Oil has a lower heat capacity than water/glycol, so its not the ideal coolant. But oil cooling of heads does work (BMW motorcylces, Hoover HVX mods, etc), and this is a lot simpler and cheaper to implement than water-cooled heads.
    For consideration.
     
    Last edited: Aug 23, 2019
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  5. Aug 24, 2019 #305

    Pops

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    The only down side to the HVX mods that I have found was a reduction of about 8-10 pounds of oil pressure at cruise rpm of 2650/2700 with the extra flow. To get the oil pressure up that amount, I went to a .0025" thick oil pump cover gasket instead of the stock .004" thick.
     
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  6. Aug 24, 2019 #306

    Pops

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    First time I have see an pictures of information of anyone building a mag mount for the pulley end. I have mine partly done. Built the same way except the bottom of the mount is also part of the cross over bracket that is part of the bed engine mount. The top attaches to the 8mm studs at the generator studs.
     
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  7. Aug 24, 2019 #307

    blane.c

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    Checking formula - mph x (88/rpm) x 12 = pitch - did you have about a 32" pitch (it works out to 31.8" to 31.2")
     
  8. Aug 24, 2019 #308

    Vigilant1

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    Do you think it is worth going to a higher output oil pump to keep the pressure up (and allow even more oil to flow to the heads)? The stock Type 1 pump has 21mm wide gears, the Type 4 (up to 2000cc) went to 24mm wide gears, and aftermarket 26mm and 30mm pumps are available. Bigger isn't always better--it is easy to get in trouble by having too much oil volume/pressure with a too-big pump (especially when the oil is cold). But, if the HVX mods are opening things up to allow more flow through the passages and to the head (which we want), maybe the larger pumps make sense?
     
    Last edited: Aug 24, 2019
  9. Aug 25, 2019 #309

    Pops

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    I had a 26 mm pump.
     
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  10. Aug 25, 2019 #310

    Pops

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    This is as far as I have gotten on my flywheel drive VW engine. Bob Hoover's bed mount. Will be drilling a lot of lighting holes before I'm finished. Turned 2 mag drive rings. Need to finish the prop extension and the parts for the pulley end mag drive. I used the Oil Pump bottom 2 , 8mm studs for mounting the part for the bed engine mount because the large tapped bosses on each side of the case is just in the later Universal case. IF I was to do it again I would use those bosses and run the bracket down around the bottom of the pump so the pump cover could be taken off without removing the mount. For the non-Universal case it would be done the way I did it buy using the oil pump lower studs. Haven't done anything with the flywheel drive for a couple of years , trying to get the JMR finished.
     

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  11. Aug 25, 2019 #311

    lakeracer69

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    I've been looking at a lot of build videos and parts, are these lower cylinder tins used for an A/C engine? Obviously, you have to baffle everything under the cowl, but are these used as well?

    The ones in the link are for a type 3 motor, but say that they can be used on a type 1 including big bores.

    https://www.mamotorworks.com/VW/pro...h-aftermaket-pieces-for-hotter-climate_377506

    They look more thought out than the regular type 1 deflectors that just go between the lower cylinder area. Either one ok, one better than the other, or you never use those?

    Thanks
     
  12. Aug 25, 2019 #312

    Vigilant1

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    Yes, these "cool tins" are considered mandatory--or at least I know they are on 2180 and above engines. They keep the cooling air moving through the fins on the bottom side of the cylinders.
    Here's a link to the ones GPAS sells: http://www.greatplainsas.com/sccooltin.html
    In theory, flat black ones would be preferable to other colors/finishes, but I don't now if there's a measurable difference in real-world performance.
     
    Last edited: Aug 25, 2019
  13. Aug 25, 2019 #313

    Hot Wings

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    They should be.

    Just like the simple little plate deflectors they too should be safety wired in place.* The spring tension on the stud clips isn't enough to always keep them in place, even on a ground bound VW. When they come loose they start to saw through the head studs. I've never actually seen a stud break because of this but when >20% of the area is missing because of a sheet metal thick notch - it makes you wonder.

    I've seen them wear a hole in the top of the pushrod tube as well when they come loose.

    100 hour inspection item. Reach in there and see if they wiggle.

    * some versions have tabs on them that let them be sandwiched between the stock VW shrouding with the 6mm screws.
     
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  14. Aug 25, 2019 #314

    cavelamb

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    Yes. But also cooling the oil is just as important.
    This is how I worked out those two details on a 2180.

    The oil pump was replaced with an oil filter adapter.
    The simple debris screen of the automotive engine is
    not at all adequate. IMHO.

    I've seen oil coolers with many feet of hose running back
    and forth. I can't imagine how that affects oil flow.
    This one had the 90 degree adapter on top of the engine
    and cooling air is ducted directly to the oil cooler.

    Before the inlet was added oil temps went way too high.
    But after the duct was made no problems ever.
    Oil temperatures were normal and very stable.

    If I were to do it over again I would be a lot more aware
    of weights. The Great Plains intake manifolds are steel
    and very heavy for what they do. Aluminum or thin wall
    stainless would be so much lighter.

    The Diehl accessory case seems like such a cool add on.
    But for the weight it adds.
    I would not do that again. A simple mag mount (like above)
    would be fine, and it may be possible to adapt an alternator
    into that design as well. It would be a lot more development
    effort. The bolt on case is so simple. But the weight reduction
    would be worth the effort.
     

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  15. Aug 25, 2019 #315

    Turd Ferguson

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    Is that a Pober Pixie with the 2180? How's it fly?
     
  16. Aug 26, 2019 #316

    lakeracer69

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  17. Aug 26, 2019 #317

    Pops

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    Why ?
     
  18. Aug 26, 2019 #318

    TFF

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    I would think a bigger sump would be a nice addition. Has to help oil temp even if at an acceptable temp. Weight maybe not wanted, but I like oil. Lakeracer is building something aerobatic if not keeping track.
     
  19. Aug 26, 2019 #319

    Pops

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    4 more qts of oil will just take a little longer to come up the running temp. The only cooling effect would be the extra surface area of the larger pan. A little more efficient oil cooler would do as good or better with almost no increase in weight. I would rather have my hot oil box installed ( that weighs a 2 -3 oz ) that cooled the oil 20 degrees than the weight of the sump and 4 qts of oil. But, if weight is not a factor, go for it.
     
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  20. Aug 26, 2019 #320

    lakeracer69

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    What TFF said above. ^

    What can I say, I like oil. I didn't realize that these things only have a 2.6 quart stock capacity. Small wonder oil problems are an issue. Maybe low oil capacity is the forth thing that doesn't help you when you have an engine failure. The first three being:
    Altitude above you, runway behind you, and fuel back in the fuel truck. I'd take the weight penalty on that if the pan fits between the engine mount.

    My 103 cu. in. Harley has more stock oil capacity.
     
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