Posts: 1518
Joined: 10/2/2002 From: Portage,
IN, USA Status: online
Thank you for the parts, Proptop!
The eBay win came in yesterday and it spent a half day soaking in Hoppe's No. 9 gun cleaning fluid and it cleaned up very nicely.
Now comes the time to fit the parts you sent, but I would like to dis-assemble the case, cylinder and piston but I've never had one apart before and don't quite know whats involved.
I see there are two sections to the cylinder. The upper cylinder is all aluminum with the base of it being steel. Is this simply an aluminum sleeve that is shrunk on or is it screwed into the steel? Another question would be where do you wrench this thing? Would I need a wooden block and a vise to grip the cylinder? After I cleaned it in the Hoppe's it brightened up a brass or copper gasket under the cylinder I hadn't seen also.
I think I might have to hunt for a Wen-Mac wrench now. All that I have in my collection is just about every Cox wrench made, but no Wen-Mac style. Is any of this possible with the Cox varieties like the backplate? I would hate to chew this thing up with the wrong wrenches.
There is a pin already in the crankcase casting. It appears it is simply a pin, no type of head on it. If you look close you can see it in the first picture. It must be just to keep the recoil from spinning and not to hold it to the case.
Was there ever a spring to keep the needle valve tight on these early ones? There is nothing to keep the needle from free turning on this one....
When the backplate is off, do I drive out the crankshaft like on a Cox? Is it splined?
< Message edited by jetpack -- 6/21/2007 6:47:39 AM >
Posts: 4464
Joined: 10/18/2002 From: Rome,
NY, USA Status: online
That one's in nice shape! The upper alum. part of the cyl. is screwed on, as is the lower steel part, down into the case. I wish I had a Wen Mac wrench for ya...but...
There should be a gasket up inside the alum. finned upper "cap" ...it's just basically the head that threads down over the steel sleeve. IIRC the gasket is black, and relatively soft, like perhaps asbestos treated with that black kind of slightly rubbery whateveritis?
There is also a copper gasket at the cyl. base.
I think that lower pin is a locating pin...and I believe that rear recoil housing had one still stuck in it? There might be a hole in the front of the venturi, just above the spraybar where the upper rivet/pin (whatdidyacallit?) holds the R. recoil housing in place?
The flywheel that's on there now is pressed on and yep, the crank is splined...(I hope the crank splines on yours and the hole on the flywheel/one way I gave ya is the proper dia. to fit...I don't know if they were all the same size, or if there were variations?)
I think there's supposed to be a spring on the N.V. (I used to use a shortened ball point pen spring ) but none of the ones I ever got had one either?
Cheers!
< Message edited by proptop -- 6/21/2007 8:00:27 AM >
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It's bad luck to be superstitious... Revver Bro #77
Posts: 459
Joined: 11/18/2005 From: Cincinnati,
OH, USA Status: offline
Here are some disassembly hints based on being sent a thoroughly gummed up Mk III by my nine year old son who bought it for $3 at a church rummage sale. I think running Cox .049s at Spring Break got him hooked.
Since I don't have any Wen Mac tools here's what I managed to do to free it up and take it apart:
After two weeks soaking in powersteering fluid and penetrating oil I could turn it over at the prop nut with my fingers. I found that by spreading the business end of an AP .061 wrench a bit (its soft and easy to do) it can be used to take the head off. The wooden wrench trick might work on the cylinder, but it is very tight between the and intake stack and it will take some thought. Get ready to cringe, but since this engine already had some wrench marks on the aluminum head and the cylinder fins, I got the cylinder off with an old pair of pliers and a bit of chamois between the nut busting teeth and the fins. The gasket inside the head is a bit crumbly bit still seals I wonder what it is made of? Almost looks like ancient rubber! I opened the backplate with end of a Cox .049 wrench that is sometime used to remove the Cox cylinder at the exhaust slots when there are no flats on the top fin. I needed to cut a new paper gasket for that since the old one came out in pieces. I cleaned up every thing inside with the solvents on hand, q-tips, and soft cloth. When I reassembled the engine it turned smoothly. I finally put a prop on after rummaging around for a hex nut and a washer that fit. For some odd reason I expected it to be 5/40. When I put a short plug in the head it flipped with pretty good compression even with the crumbly gasket. Need to replace that. James was really happy when I told him his rummage sale find was probably ready to try to start when he comes down for July and August.
BTW, the crankcase and cylinder/head of your engine look dead on like this Mk III, which apparently has never had a spring starter unit just a thrust washer/prop driver.
PS: anybody got some idea of how to reset the ball joint into the piston on one of these?
PPS: I sanded the outside of the head lightly to clean up a few nicks and after that the both the AP and the Cox plug wrench fit the head.
quote:
ORIGINAL: jetpack
I won a Mk II in good condition with a tank and what looks like a string-start pulley which would be a proper way to start these ducted fan dealies - just not correct to print and what I am striving for.
Now it just has to be paid for and shipped, then I can tear it down, clean it and polish it. Is there anything I should be aware of or tricks to taking a Wen-Mac apart?
I won it for $9.99 and was the only bidder. I am charged. What lies next I guess would be to scrounge for a basket case with a good recoil and try and convert this one. I am not sure if removing that recoil is possible. Has anyone tore into one? I think someone said they are rivited ???
< Message edited by lildiesel -- 6/6/2008 8:42:11 PM >
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Joined: 11/18/2005 From: Cincinnati,
OH, USA Status: offline
Interesting. In the diesel world I know a screw on aluminum top is a muff, but a diesel muff only provides cooling fins for the cylinder and a place to locate the compression screw over the contrapistion. On the Wen Mac the whole thing is actually the glow plug head with the combustion chamber as well as the cooling fins. To my mind it makes much more sense to call the Wen Mac part the "head" instead of just a "muff".
Does anybody know the material for the gasket in the aluminum head? The seal is clearly crumbling in this Mk III and I prefer not to have to go the trial and error route while replacing it. The seal is exposed to the combustion process directly and nearly 1/16th thick Would a Viton quad ring suffice? Or am I looking at cutting something out of asbestos gasket material?
BTW The first hex nut I dug out of my parts drawers that fit the prop shaft was a brass 8-32 from the plumbing bits. I later found a steel one, but need to rummage at the hardware store for a suitable washer with a larger OD than the 3/8 across the nut.
quote:
ORIGINAL: gcb
BTW, the screw-on aluminum top is often referred to as a muff.
George
< Message edited by lildiesel -- 6/6/2008 8:19:04 PM >
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Joined: 12/11/2001 From: Rex, NC, USA Status: offline
Well,.. I've always just looked at them,.. & said "Yup that's an old/new/slag WenMack & chucked them in the drawer till I used it (yeah.. I use them ) The old WenMacks were pretty good,.. the glow plugs will exchange with an Atwood Wasp.049... The McCoys were good,.. made "OK" power... the new "Testors/McCoy" slag engines were lumps... But.. what you need for a vintage D/F build is the old Veron ducted fans for 049-09..IF you're going to build a "vintage d/f model. I have plenty of plans for the vintage d/f models.. before they became kits. they show aluminum fan bending,.. BUT,.aluminum gets brittle and will throw a blade.. like a Ginsu knife. The nylon d/f blades manufactured by Veron are a bit safer.. but seriously, if you're going to build a D/F model.. make it ELECTRIC ducted fan. I took the old Cox Airlifter electric fans with the lame 6volt motor, and transplanted a brushless EFlite 370 inside. It took the meger 2 oz thrust d/f, and turned it into mega thrust on 11.1Volts. BUT,.. that's another forum.. If you insist on D'F with I.C. engines.. think diesel. The Veron .049-.09 fans are for diesel, and will turn them with the power needed to fly that model nicely! Oh,. and if you look at the photos,.. when was the last time you saw a .049 spinner that was 2-piece & screwed together? Yeah... I'm old,.. neener-neener! )
< Message edited by Demon-Leather -- 6/23/2008 10:37:06 PM >
Posts: 1518
Joined: 10/2/2002 From: Portage,
IN, USA Status: online
Did OK Cub make diesels? Here's an .074 I see up for sale. Wondering if it has the same overall dimensions as the .049 besides the displacement. This one says its missing the compression screw.
I have a couple of Veron fan blades, one is better than the other. The one is warped across the hub web (shrinkage) but could be trued up on a lathe, plus I don't have that small ring washer that you have pictured. Just a starting pulley with each. The better one I have nicely sanded and balanced.
I like what Japanman suggested...stuffing the MKII with some modern parts! All that type of work is possible for me including EDM.
< Message edited by jetpack -- 6/24/2008 11:23:09 AM >
Posts: 1518
Joined: 10/2/2002 From: Portage,
IN, USA Status: online
Could you imagine how much fuel and oil a person would be wearing running that diesel? I've never fueled up my OK Cub or Wen-Mac yet but can imagine they leak as fast as they burn it. There's no sealing material between the backplate and the stamped and sheared tank with screw and metal washer. I'm sure it could all be sealed up better. I've tried a servo grommet in the fuel hose hole and a small diameter fuel line and that made me feel better than just stuffing a fuel tube through the hole.
< Message edited by jetpack -- 6/24/2008 8:34:09 PM >
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All Forums >> RC Airplanes >> "1/2 A" & "1/8 A" airplanes >> RE: Early Wen-Mac Identification 
RE: Early Wen-Mac Identification - 
When I put a short plug in the head it flipped with pretty good compression even with the crumbly gasket. Need to replace that. James was really happy when I told him his rummage sale find was probably ready to try to start when he comes down for July and August. 
) The old WenMacks were pretty good,.. the glow plugs will exchange with an Atwood Wasp.049... The McCoys were good,.. made "OK" power... the new "Testors/McCoy" slag engines were lumps... But.. what you need for a vintage D/F build is the old Veron ducted fans for 049-09..IF you're going to build a "vintage d/f model. I have plenty of 
RE: Early Wen-Mac Identification - 
