jetpack

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oooo AWESOME! One PM comming up...........

jetpack

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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?

proptop

My Feedback: (8)

That one's in nice shape![8D]
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![sm=thumbup.gif]

lildiesel

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.

gcb

BTW, the screw-on aluminum top is often referred to as a muff.

George

lildiesel

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.

Yuu

Look for a 'Fender Washer' w/ small hole and large O.D. then put it on a small bolt in the elec drill and file it down to size.

lildiesel

Thanks. How often do we forget the simple solutions?

BTW, I finally cleaned up the outside of the crankcase completely and danged if this isn't a Mk II instead of Mk III!

Demon-Leather

My Feedback: (10)

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!)

jetpack

My Feedback: (1)

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.

Demon-Leather

My Feedback: (10)

Yup.. they sure did, & that looks like one of them... You can probably find a compression screw fairly easy for it... Bob

jetpack

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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.

Demon-Leather

My Feedback: (10)

Believe it or not.. it doesn't leak. It DOES siphon if you don't plug one tube! (like a paint sprayer!) I took a lead from Eric Clutton & add vanilla lamp oil fragrence to my home-brew fuel.. so you , your clothes,.. and nose hairs smell like a vanilla ice cream float!

gcb

There was both an .049 and an .074 (sold as .075) diesel. I had the .075 but not the .049. The one pictured appears to be missing the screw-on head AND the compression screw. At one time OK used a spring to adjust the diesel to an "optimum" setting and there was no screw adjustment. Never an one of these so I don't know how well it ran (if at all).

Some of those tanks came with a fiber washer for the screw to seal it. Never had problems with mine. Whatever position the engine is mounted, the tank should be rotated so the tubes point up. That way, when tubing is inserted in the hole, the pickup will extend to the lower outside of the tank.

This tank was not meant for stunt, just 'round and 'round.

George

RedNeck Pilot

What is the engine in the first picture I have one and I can't figure out anything about it other than it's a .049?

jetpack

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Which post number, Red?

I looked back and the first pic is the two blueprint pics I had up?

RedNeck Pilot

It was post#3.

jetpack

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That is a Cox .049 Thermal Hopper. The crankcase could be fitted to a metal tank and called a Space Bug also. There's also a factory "bird cage" mount for it that spaces the engine out to clear the carb from the firewall.

RedNeck Pilot

Cool thanks.

gcb

Red,

A little extra info. The Space Bug was released first, then the Thermal Hopper a bit later. The cage mount apparently didn't sell well, and I've heard that Leroy Cox threw out a whole bunch of them.

The Space Bug, Thermal Hopper, Space Bug Jr., and Strato Bug all had intakes protruding from the rear which necessitated either adding a spacer or drilling the firewall. I opted to drill the firewalls. This in turn necessitated the need to have an opening in the fuselage for air to enter, and preferably stick your finger in to choke it.

Even though they were a PITA to mount, they are all excellent engines. Cox saw the light and made the Babe Bee without need to drill for the intake.

George

RedNeck Pilot

Yea I was thinking about building a P51 and bending a piece of tube around and out the piece where the air intake is on the full-scale. I don't know how it'll work but it sounds neat.

gcb

You might want to think that out a bit. Remember the scoop is toward the rear of the wings so the tube would need to be quite long and a bit heavy. Of course it is doable if you want to do it that way.

Something to consider is to mount the Thermal Hopper to the firewall by drilling a hole the diameter of the intake tube, removing the intake nut and needle assembly, mount the engine, then replace the needle assembly and intake screen nut. Of course you need to remove all of this to fuel proof and paint.

Leave a hole in the bottom of the fuselage to choke and drain. Of course if you mount the engine inverted, you need to pace the hole elsewhere.

The first time I mounted a Thermal Hopper I did it that way. The cylinder was mounted upright and the plane was a CL Bluetail Fly from a model mag in the mid fifties.

The first new engine I had was a Cox Space Bug Jr. which I installed in a Scientific Little Devil. Drilled a hole in the firewall and front of fuselage and choked from the bottom.

George

john schicker

hi guys is there anyone got any old wen mac motors or wasp motors lying about that they may sell please email me [email protected]

Demon-Leather

My Feedback: (10)

Geeeze!... Since we're talking everything here.. just drop everything else, and go for the OKCub.049...
The I.D. is EZ... Look at the photos.. OKCub .049 "A" Plastic red tank, Firewall mounting like Cox only. OKCub .049"B" Dual monting lugs.. both vertical firewall & horizontal beam mounting, aluminum rear tank, usually anodized red, but can have "natural finish". They're slow, but steady & dependable, and will always start 1st to 2nd flip... enough said! Bob

gcb

Almost enough said.

Neither of the engines shown appear to have the standard OK needle. Be aware that some of the stock needles have a blunt tip that takes it slobbering rich to full lean in about one turn. You can file more taper on the needle to correct that.

George