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  1. #1
    lildiesel's Avatar
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    Refurbishing a Wen Mac Mk II?

    Does anyone here know of what material the head gasket in the aluminum muff of a Wen Mac Mk II is made?

    The example I am cleaning has a black gasket of what looks and feels like old, baked rubber. Except for having a square cut edge and a flat inside diameter surface, for the life of me, it looks like someone put a neoprene O-ring in there. Is this what the head seal is supposed to look like on this engine? There are some light tool marks on the muff and the lead steel cylinder, so someone has opened this engine up and worked on it in the past. Otherwise, cleaned up the engine looks in very good condition and complete except for the ribbed spinner nut and the needle valve spring.

    Right now the engine turns over smoothly and the piston/cylinder fit seems very good. With a prop and a short plug in the head it flips with a satisfying plop, but the compression seems low compared to a Babe Bee or even a Cub B. I'd like to replace the gasket before attempting to run the engine. What I don't know is what the gasket is supposed to look like and of what material the OE gasket is made. The one in the muff is 1/16th thick (hence the O-ring thoughts) and the way the muff/head is made the thickness of the gasket determines the compression ratio.

    Any input you might have would be greatly appreciated. My experience with Wen Mac .049s is limited to getting a Hawk tether car running by turning over a trike and having the owner crank the front wheel while his sister complained she wanted to ride. Obviously I've never even taken a glow head equipped Wen Mac apart, let alone a Mk II.

    You should also know this is a "Dad, can you fix it?" project.

    My nine year old son bought this seriously gummed up Wen Mac for $3 at a church rummage sale. He's just starting to learn how to start and run my old Cox .049s so he was pretty pleased to find an engine of his own. His mom mailed it to me in a bubble pack envelope and when I got it I was surprised to see it had a head that required a glow plug, had the needle valve, but no prop nut. I guessed it was a Mk III (the crankcase was really filthy) and since it wouldn't turn over with thumb and forefinger I opened up the back plate and put the whole thing in a small bowl of power steering fluid mixed with pentrating oil and set it on the sill of the sunside window of my garage. Two weeks later when I remembered it was there I checked it drained the oil out, wiped it off, and it turned over freely!

    When I disassembled the engine and cleaned up the case I could finally read the stuff cast on the case and was surprised it was a Mk II. That got me hooked since my kid picked up a neat old engine in decent condition and I'd really love to make it a runner for him.

  2. #2

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    RE: Refurbishing a Wen Mac Mk II?

    I sort of remember the original style Wen-Mac engines, for they were on simple controlliners, then after a few bumpy landings got set on to Radio aircraft. But each of them did not have a muffler of any design. Perhaps why Cox went to the Q-Z design.

    But you need to contact a fellow in Fontana Calif. who has numerous parts from 1/2 A engies of many designs. I used to see him at the AMA convention, but he has difficulty in standing now, so often sells his parts on the "Bay" instead. And thus may be easier to contact via there.

    He ain't cheap. He ain't easy to get ahold of. And he isn't fast in mailing either (even the simple 10 miles)

    Wm.
    Thousands of Laser Cut parts, thousands
    And plans too

  3. #3

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    RE: Refurbishing a Wen Mac Mk II?

    Hi i also would like to know what the material gasket is made from as i have afew Wen Mac motors without the head gasket .it would not be a o ring because of the heat around the plug .common guys give us a lead .....john

  4. #4
    lildiesel's Avatar
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    RE: Refurbishing a Wen Mac Mk II?

    Do the gaskets in your working Wen Mac engines look like the one I describe in color and thickness?

    It looks like I'd need to fashion a flat gasket 1/2" OD. 3/8" ID and 1/16th thickness to replicate what's in my engine. If I choose a thinner material I'd be raising the compression... of course, I want to replace the gasket because the compression seems a bit low on this thing.


    ORIGINAL: john schicker

    Hi i also would like to know what the material gasket is made from as i have afew Wen Mac motors without the head gasket .it would not be a o ring because of the heat around the plug .common guys give us a lead .....john

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    RE: Refurbishing a Wen Mac Mk II?

    Wen-Macs were lower compression than Baby Bees, and were not as powerful. Don't compare them to Cox products, as Wen-Mac are an eariler design by Atwood, like the Shreik, and Wasp. They also have a bit in common with the OK Cub. A good Wen Mac puts out less power than a Baby Bee with a single port, this is why Cox put everyone out of business in the 1/2A engine market.

    Anyway, I beleive the gasket was some sort rubberized fibre material. Most I have seen still seal. I suppose neoprene o-ring, or quad ring would work, we use them on gasoline racing motorcycle head gaskets and they hold up quite well. Keep in mind an alcohol engine runs much cooler than gasoline and I think you'll see neoprene/buna will be just fine.
    Did you charge the transitory remitter batteries ?
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    RE: Refurbishing a Wen Mac Mk II?

    The Wen Mac was actually much stronger than the Baby Bee, with three exhaust and three intake ports, the intake ports were between each exhaust port, the piston was conical with a smaller concentric flat top. This pushed the intake up toward the top of the engine. Very good design, but some quality control issues as I recall. Atwood's design outperformed all of the Cox engines at the time. He went on to design the Cox TD series as I recall.
    Glow Head Brotherhood #15

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    RE: Refurbishing a Wen Mac Mk II?

    Does anyone here know of what material the head gasket in the aluminum muff of a Wen Mac Mk II is made?
    I think you are confusing us. I don't recall a rubber head gasket, but then I was a kid the last time I took one apart. In fact I know of no model engine of any size that has such low heat that a rubber head gasket can survive. What do you mean by alluminum muff? Was this a muffler gasket?
    Glow Head Brotherhood #15

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    RE: Refurbishing a Wen Mac Mk II?

    The original gasket is some sort of fiber based stuff. I think a black O-ring from the hardware store will work just fine. My wife got a half dozen Wen-Macs cheap at an auction. I kept the two oldest and sold the others at swap meets for $5 each, making a tidy profit. The two I kept took some breaking in before they became friendly little engines. I intend to someday put them on park-flierish airplanes.

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    RE: Refurbishing a Wen Mac Mk II?

    could someone purchess a few of these gaskets as i would like 6 to compleate my motors and get them running Regards john
    My email is johnschicker@clear.net.nz

  10. #10
    lildiesel's Avatar
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    RE: Refurbishing a Wen Mac Mk II?

    Many small diesels have a screw on set of cooling fins that fit onto the steel cylinder and also locates the compression screw on the contrapiston. It is often referred to as a "muff". The Wen Mac also has an aluminum "muff" that screws onto the steel cylinders. It also serves as the glow head for the engine. The compression seal in this Wen Mac Mk II appears to be some kind of rubber and fiber material essentially a flat washer with OD 1/2" and ID 3/8"

    In the picture below you can clearly see the aluminum muff. A screw on cap of cooling fins with a combustion chamber formed inside the top and tapped for a glow plug.

    ORIGINAL: Sport_Pilot
    What do you mean by alluminum muff? Was this a muffler gasket?
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  11. #11

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    RE: Refurbishing a Wen Mac Mk II?

    .I have taken the head off the barrell and noted that there is a resess for the gasket to fit on top of the barrel and as the head is screwed down it gecomes a tight fit between head and barrel ...john

  12. #12
    lildiesel's Avatar
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    RE: Refurbishing a Wen Mac Mk II?

    It's beginning to seem as if a Viton quad ring might do the job. I've been flying my OK Cub .049 diesel with a Viton o-ring sealing the contrapiston and have yet to need to replace the first one. Why did I order a package of 25?

  13. #13

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    RE: Refurbishing a Wen Mac Mk II?

    Hi i have started to make my own and almost got the motor to run .ie batt a little weak on charge i am using a fibre gasket .will keep you posted ....john

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    RE: Refurbishing a Wen Mac Mk II?

    A post above said the Wen-Mac is stronger than a Baby Bee. If that was the case, then why isn't the NFFS Nostalgia 1/2 A free flight class contests results reflecting this? You don't see Wen-Macs winning today in the contests. Any Cox reed engine, like a Thermal Hopper, Space Bug, Space Hopper, or even a Space Bug Jr., and the Baby Bee easily out runs them.

    If Wen-Macs were better engines than Cox reed .049s, the prices at Collectos, and on eBay would be out of sight for them. Proof of this is seeing what engines like a Fox .o49 FAI, Holland Hornets, and Nostalgia legal Cox engines sell for.

    The sad fact is Wen-Macs, especially the AMF ones, were just not as powerful as contemporary Cox engines of the same era. This does not mean they are bad engines, just not as powerful. To use them, you just have to build a slightly smaller, and lighter plane to get reasonable flight performance. I always liked the Wen-Mac rotor starter, it was simple.
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    RE: Refurbishing a Wen Mac Mk II?

    I measured the head gasket in my spare wen-mac "muff," and the dimensions are as follows:

    Thickness: 0.025" (just under 1/32" = 0.03125" )
    Inside Diameter: 0.407" (~13/32" = 0.40625" )
    Outside Diameter: 0.507"

    As is suggested above, the material seems to be some sort of black fiber.

    While we are on the subject of wen-macs, the wen-mac engines had one major advantage over cox engines. This was that wen-macs were easier for beginners to hand start. With a cox engine, even if everything was right, there was a 50/50 chance that it would decide not to run. It seemed that if the fuel was old, if the glow battery was weak, if the reed valve was gummy, or even if the weather was not just right, then there was a good chance that a cox would not hand start. However, as long as the glow plug was good, there was a pretty good chance of starting a wen mac (even with a poor glow plug battery and old fuel). Also, wen-mac's plastic planes we more detailed and durable (and also heavier) than cox's (in general).

    Last summer, I made a small motor mount and ran several wen-mac engines. The results (if I remember correctly) are as follows:

    Wen-mac Mk. III
    4.5" dia. 3-bladed wen-mac prop
    12K-13K

    Wen-mac Mk.III and Wen-mac Mk. V
    5" dia. 2-bladed wen-mac prop
    13k-14k

  16. #16
    lildiesel's Avatar
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    RE: Refurbishing a Wen Mac Mk II?

    Thanks. That's exactly the kind of information I need about the head gasket for this Wen Mac Mk II. It's good to know that the gasket should be 1/32". When I measured I was thinking that the gasket was squished flatter than it originally was.

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    RE: Refurbishing a Wen Mac Mk II?

    As a kid in the 50's when the Wen mac was introduced it was not too affectionately known by the term' When is it going to run mac'. They were cantankerous little devils till you got used to their idiocyncracies. They were plaged by quality issues, the lack of a glow head was a serious omission as it made the engine inefficient, all of the other 1/2A's of the period suffered from the same problem. That is 80% of the success story of the Cox offerings.quality was the other 20%. The props that came with Wen Macs were little more then flat bladed, overly flexible paint mixers. The biggest problem with them was that they needed a HOT plug and a GOOD FRESH battery to get them going.You also had to be generous with good fuel and at least 25% nitro.
    With all of that said I had fun with them and as quoted they wern't the most powerful, but did deliver a reasonable measure of pleasure to an 8/10 year old kid.
    Dennis

  18. #18

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    RE: Refurbishing a Wen Mac Mk II?

    For Xmas one year( I think it was 1961) my cousin and I got a pair of Wen-Mac P63 King Kobras, all chrome with the 4 and 2 blade propellers and releasable tanks that were dropped via a third line on the handle. It also had a canopy that opened.

    I remember it took quite a long take-off roll, about 3/4 of the circle, but it sure looked good in flight. Of course the chrome around the nose quickly turned grey due to the fuel, and began to come off. Within a few months, the whitish plastic under the chrome plating began to show, and soften. The little fuel line outlet molded into the fuselage broke off within 6 months which ended the Kobra's flying career. By contrast, an Aeromite was a much better flyer, but nowhere near as cool looking.

    As to the comments about Cox engines being hard to start...well to some degree I have to agree. That said, everytime I was at the local schoolyard and ran into other kids who could not get their Cox powered PT-19, Stuka, P-51, or P-40 running, I had them started with a couple flips everytime! There were guys who could get them started everytime, and others who just never got the hang of it. This held true of the same individuals when we transitioned to larger K&B and Fox .35 controline engines....mine always started first flip, while the same guys would eventually give up ask me to crank up their engines. Needless to say, as aresult i got to fly alot of other guys planes!!
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    RE: Refurbishing a Wen Mac Mk II?

    Hi guys .Back to the wenmack prob with starting .I have had troubles starting a few which i have purchessed from the states and after studing them i noticed at the bottom of the barrell 3 lugs that protrudefrom the barrel .so i decided to make a fiber Gasket from a commen sump gasket that you would use in your car sump plug .thus i reamed out with a dremmel stone and made slightly larger than the lugs so when it is screwed down it formes a good seal between the barrel and case of the wen.Mack ie gasket should not be too thick .i moved it backwards and forwards across emery paper if it is notoutside the lugs Fuel wont go past and enter the chamber wheras the cox have single or double buypass cut into there barrels .Please comment if i am on to this prob .......john from new zealand

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    RE: Refurbishing a Wen Mac Mk II?

    Hi to all .Well sucess at last Replaced head gasket and barrel gasket on two motors and they both run like new .if you kneed any info or Gaskets please email me .Kind regards john

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    RE: Refurbishing a Wen Mac Mk II?

    Lildiesel,

    That Wenmac in your picture was a special version made for the Wen Mac "Aeromite" plastic CL model. The center mounting stud and red spinner are sure give aways.

    When Wenmac first released the Aeromite the WenMac engine wasn't ready yet so you will also find them with OK Cub .049, Wasp .049 and Baby Spitfire .045 engines.

    When you find a Wasp .049 with a center screw in the backplate don't think some hacker did it. It was on purpose.

    The Baby Spitfire had a special long tank that had a center mounting post screw.

  22. #22

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    RE: Refurbishing a Wen Mac Mk II?

    Hi produced good gaskets would anyone have old spitfire motors and wen mack motors lying around email johnschicker@clear.net.nz


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