jetpack

My Feedback: (1)

I am attempting to replicate a couple of Berkeley Models ducted fan kits and need to identify what "Mk" number each of these engines are. One is obviously a pull-start version, Mk version unknown. The other looks to be a Spring Start (with Pulley?), Mk version unknown.

Drawings are dated 1958 for the pull string, and 1957 for the spring start. I am probably going to have to piece these, so having the verision numbers would be real helpful, or if that pulley on the spring start is some kind of extra that was put on the drawing.

burtcs

jetpack:

The engine should be marked with a MK# on the left hand side of the crankcase ( the side oposite that shown in your drawings). MK's I, II, III, V are common. I didn't know they produced a pull starter but live and learn. They must have been whimpy models to fly with a Wen Mac fan. Spring starters were or were not rivited to the crank case as I sure the recoil starter would have been.

I do have an OK Cub with a pull starter on it if that helps.

regards - Steve B.

jetpack

My Feedback: (1)

Hi Steve, Thanks for your response...it does help some. I never owned either of these style engines and have no idea if any of the parts that involve the recoils are repairable or removable or what to really look for. The drawings are a little non-descript as far as that would concern, but knowing how they are marked is a help.

So far my engine collection does include the OK CUB 049S which is the pull-start with the red anodized tank, never used and picked it up for 30 dollars. I felt lucky when I won it but I think they are still available. Not really sure if they are the pull start version or not, but either way I was happy to find one in new condition with its origins comming from the 50's and not very popular.

I have a Thermal Hopper that I bought in good used condition also, that one is reserved for the Sky-Ray kit that I have to copy. Now that Sky-Ray kit shows both engines, the Cox and the Cub. The Tiger gets a PeeWee that I have new that really haven't changed a bit since the day they started making them.

The Crusader and the Shooting Star are the only two that call for a Wen-Mac brand. I could replace the ducted fan idea with the Crusader because oddly enough, the plans suggest a Space Bug on the front as an alternative way of powering it with just a standard propeller and a nose cone. I have the tank assembly if I wanted to sacrifice the Thermal Hopper from the Sky-Ray for the Crusader, but then it's not a ducted fan.

So, anyways, all this leaves me with is finding the two Wen-Mac versions, and I would be able to replicate to the drawing each of the planes as far as the engines are concerned.

Now that I think about the entire deal, I would need an extra blade for one of the 049 versions if I want to stay with my desire to keep the kit contents intact, plus that PeeWee blade.

Jim Thomerson

Apparently this didn't get posted. I have a 3 inch six blade aluminum fan. Probably OkKfor a PeeWee or a Wen Mac. If you want it, PM me your address and I'll send same. I may actually have two of them.

jetpack

My Feedback: (1)

Hi Jim,

I think I seen double too. Maybe it was that other thread I mentioned I started that you replied, but I did see your offer and I replied. I'll give you a PM. I have two posts going because I didnt know what would be a better place to post it.

BobHH

My Feedback: (18)

Well, here are the few Wenmac/McCoy engines I have. All are MkII except the Testors engine. The pull start engine also has a throttle baffle in the exhaust. I have never seen the tanks fuel tanks shown on drawing but I am sure someone would have made them. As for performance.... A Cox Tee Dee .020 will out perform any of these engines. You may do better with the Tee Dee .049 or Norvel.

Bob Harris

jetpack

My Feedback: (1)

Nice Bob, Thank You.

Yes it is strange about the tanks, as I have never seen a Wen-Mac with one. Knowing the Cub engine that I have I wonder if that is the same. Was there any common ties with OK Cub and Wen-Mac as companies?

I have seen Cub engines with and without tanks installed, and the backplates on them all have a tapped center hole for adding the tank. Do all Wen-Mac's have these stubs also? I wonder about that.

I saved all your pics in my collection so I have a solid reference to the MkII's now.

As far as power is concerned, I'll agree with what you said there. I run PeeWee's before and have to say it seemed as strong as a Wen-Mack P-40 control line model my buddy had as we were growing up. I'm not really as much concerned about that though, as I'm striving to build the four of these all period correct right to the drawings motor and all. It's not an easy project but having a decent time getting there so far.[sm=teeth_smile.gif]

injunnut1

The first drawing is an "OK Cub .074" pull start engine. The second drawing is a "Wen Mac .049 Mk II" engine. Wen Mac did indeed produce engines with the pull starter ( I have at least three .049 MkII "Wen Mac" engines with pull starters), the "Wen Mac" starter is almost exactly like the OK Cub starter except the front prop drives are a bit different. It is said by many that "Ok Cub" (Herkimer) either bought the rights to the starter from "Wen Mac" or they simply stole it ..... I might have read about the pull-starter thing in the "They Should Have Kept The Bear" publication, I can't remember, or it could have been from one of the many "Gas Toy Collector" publications? I have several of the "Wen Mac .049" engines with tanks, they even had a nice red anodized one once upon a time ..... no, the "OK Cub .049B" tanks will not interchange.

jetpack

My Feedback: (1)

Thank You injunnut,

Looks like you found a descrepancy in the drawing with how the motor is called out and how it is drawn up. Interesting! That I will have to keep in mind. What would be the clue? I wondered about how stubby the intake is on it. Seems every 049 I've looked at never had them cut flush to the casting rib like that.

gcb

Jetpack,

I don't think you will find engines that match either outline. I believe the draftsman took a bit of license, perhaps to avoid lawsuits. The first appears to be "mostly" Cub, although Cubs have straight fins, and the old crankcase had a different tank. Can't speak for the pull-starter, don't have one of those. The one on the right looks mostly Wen Mac Mk-II. I have one of those out of an old Aeromite.
How are you coming on your quest to build those Duct fan models. Feel fortunate that you are building from the plans and are not handicapped by a Berkeley kit.

George

Edit: Darn typos!!

jetpack

My Feedback: (1)

Hiya George,

Well your right about being fortunate about not building from the kit, the die-cut isnt the best but man-o-man the wood thats stacked in one. For such small planes I've never seen so much wood. And it's not just all planking either. They were'nt shy on balsa.

My quest has so far turned up a Thermal Hopper (Sky-Ray), and OK Cub Pull-Start with Tank (Shooting Star), Cox PeeWee (Tiger), two extra fan blades and a contact for my mono-line units. I have two of the four kits complete that use the ducted fan idea, and full prints for the two others that I don't. I am hoping to bump into someone that has the missing templates for those two (Crusader and Tiger) or I am facing having to loft my own. I have re-drawn what decals have come with those two kits, but still have to do the decals for the two prints I recently got.

I've contacted Midwest Balsa and have 1/20" balsa sheet on their special cut list, and have all the materials and methods for replicating the vacuu-form parts. Other bits I've collected are some midget tanks and enough Perfect brand rubber streamlined wheels with the aluminum hubs.

So I'm almost there to start laying out parts and building, so I thought it would be a good idea to start motor hunting for the two remainders. I have been doing my rc powerboat hobbies in the meantime, thats another big job but have a full boat rack going now [sm=teeth_smile.gif]

build light

Great thread! I have been sitting back and following but have not had anything to be able to contribute. Till now.

I do see a drawback to one of the materials. This would be the "duct paper" shown in that last picture. Seems to me that this would be a major problem area when it comes to exhaust residue from the engine![sm=confused.gif]

Another interesting thing I noticed was the very important plastic "nose cone" or bubble that goes over the engine to help streamline the air entering the duct. Very cool. Or may be not so cool, as it may be detrimental to the engine cooling to some degree.

Robert

jetpack

My Feedback: (1)

Hi Robert, Glad to see you're along.

That duct paper as supplied in the kit is thin white cardboard and is all die-cut. Its flat on one side and glossy on the other and the instructions call for it to be doped at least three times for fuel proofing. Both the outer tube and the inner cone is made of this material and shaped around the balsa buildup.

Adds up to a lot of weight I would think! If there was one thing that would have added to the performace of these I would have to say use a different material for that...something that is already fuel proof...but then again, this is the 50's and not a very exotic kit - just it's design.

The box touts these as being the first ducted fan kits ever produced, and probably a correct statement because I've searched the AMA magazines at the museum and the only ones around before and after these were one-off experiments that readers contributed articles on.

If you would like to see the drawings for each plus a detail or two I have posted them on MySpace. Just use the link name to find me there that I've added as my posting signature. The drawings are very large (30 inches or so each way) so they get scrunched a little trying to add them digitally, but still legible enough to see how each one is put together.[sm=thumbs_up.gif]

I think I will add the building instructions off of one for reading to the album.

build light

Not having seen the instructions what you say makes sense.

I think for an actual build I would change the material to some kind of thin plastic sheeting that has just a touch of rigidity. Enough to hold the curve. Of course plastic is rather dense and could possibly weigh more. Might require some study...

All in all cool stuff!

Robert

gcb

Jetpack,

Are these still for static display only? I think you said you were considering a see-through part to show detail last time we discussed these planes.

I did not know Berkeley came out with four of them...I only remember two. I think the Skyray was the first (~1956). The last two must have been after 1960 (while I was in the Navy). Around the same time the Skyray became available, there was a build article in a mag (AT Annual 1956, I think) for the SAAB Draken. I think the duct tube in that was Silkspan with several coats of dope. I think it was doped on a sheet of glass, then pulled off and formed after it was dry. This is from memory so I may have the process wrong.

There was a free flight group (in England, I think) that was flying ducted fans at the time. I remembered all of them as FF so I was surprised when you mentioned the Monoline CL version.

I believe interest in ducted fans wained because engines were throwing blades off the fans.

There were a few ducted airplanes before that but most were novelty planes (like Roy Clough's ships) that used propellers instead of fans.

Sorry for rambling. Like most other modelers, I find this stuff interesting. [8D]

George

jetpack

My Feedback: (1)

George,

Yes, I would like to try a cut-away view that would display the fan and engine, as the heart of the design is mostly hidden from view and if I can get a Mono-Line unit I would like to have that exposed also with clear covering instead of hidden below tissue and dope.

There's lots of nice lightweight transparent coverings now and would be perfect for that half of the plane or even the entire airframe if my building skills are up to making a nice build. The fuselages are all strip covered...something I've had no exposure to yet. I wouldn't like if I had to use fillers to cover mistakes that the covering would show, so we'll see what happens there. If I can pull off a nice clean build, I won't hide it and use it for a transparent covering job.

I have all four drawings now, but only two full kits. Berkeley actually came out with six of these kits, but two of them were Jetex power and don't really fit into the ducted fan catagory. Four of them is plenty to fill my plate. For being small wingspan models there's a tremendous amout of building involved in each of them.

Your right about seeing how to make that thrust tube and it was a Draken. There's another one out there also which is a Panther design. Veron of England had a few kits and fans available. They molded their blades out of pure nylon, and I even have a couple of those. They offered them in quite a few different sizes. On my examples I noticed even though the pattern making of them is acceptable, they were molded improperly in the press and suffer from distortion. To-date there still is no acceptable fan blade on the market that could be used with a 1/2A engine.

If I could find a suitable blade I could bolt on, I would like to try a flying example of the Sky-Ray. That one seems most likey to carry the load, plus its just one of my favorite aircraft.[sm=teeth_smile.gif]

Beeza

My Feedback: (1)

Hi jetpack--
I remember being pretty nuts over the Berkely 1/2A duct-fan kits. I bought one in the early 60's from AHC (America's Hobby Center) back then. I can't remember which one,
but it did tae the PeeWee .020--I described it that way when ordering it and they included the engine by mistake (which I still have). The little metal fan was included. It would have been very hard to start the engine inside the fuselage.
There were options for mono-line control on some of the plans.
I built one side of the fuselage off the plans, but couldn't figure out back then how to build up the other side, without 'oiling' the plans to make them transparent on the back side.
I've seen these kits go for big bucks on ebay, no doubt for collectors.
Good luck with your project!
Beeza

Japanman

This is right up my alley.
I made a couple of carbon fiber ducted fans, and if I had a good sapre, I would give it to you.
In my recent musings about making fans, I have been considering getting some aluminium and making the fan along the lines of the ones you see in the kit.
My feeling is, the problems with the old fans are that they are very likely to be made from a high purity grade of aluminium so they could be stamped.
Unfortunately pure aluminium is very weak and highly suceptable to fatigue failure.

I was thinking about using 6061 aluminium, as it is easy to heat treat at home. It can be annealed to a very soft state for shaping too, so it may be possible to make a wood block press mould.

Many people have expressed concerns about aluminium propellers. I personally temper these with the fact that many large full scale props are made of aluminium. and anyone who has ridden in a prop plane knows they vibrate like mad, so if suitable aluminium works in these instances for hundreds of hours, it is going to work on our planes.

I have a milling machine on order which I will convert to CNC when I get it. Up an running, I will use it to make some nice moulds for more carbon fans etc.
If you can wait that long, I`ll happily send you a carbon fan.

This is a great project. With a different engine and a little better fan, you might be able to install radio gear and make it fly!

Stefan

digital_trucker

Unfortunately, aluminum props aren't allowed under AMA rules. I imagine that applies to ducted fans too.

Toad

No law says you have to operate by AMA guide lines

digital_trucker

True, but it'll void your insurance.

jetpack

My Feedback: (1)

Hello Stephan,

You are right about the older blades being made of high purity aluminum. They are very close to being dead soft and I have had many warnings not to use them. But then of course, they were produced when the engines produced very little power. An exception to that would be the Thermal Hopper engine...that engine would probably work to the blades failure point. It would be instant disaster on a modern TD or Norvel.

It is too bad I no longer work in the QC field I would be able to CMM one for your reference. I would have to use standard methods to measure one up (indicators and radius gages), but it is very simple so that helps. Just visually inspecting them they are constant pitch from root to tip with the root width being narrower than the tips. Figuring out the swept area shouldn't be too much of a problem. This would give you a picture what was happening back then if you think it might help. Let me know if you could use it and I'll throw one on the surface plate.

The instructions point out that "a large increase can be gain in performace by sanding the leading and trailing edges to an airfoil shape". These are very basic stampings, and almost feel that Berkeley's efforts were targeted at getting the tooling to last past production, other than making a blade that would hold together. Getting one of these built far enough to pass a glide test, fueled and started would probably have been past the ability of most consumers.

I am in really no hurry on these planes it is just a pet project of mine that I turn to when other things are not so busy. As of my approach right now with the builds, they will be basically hangar queen displays just to satisfy the vintage balsa bug thats in me, but if a true blade could be built I sure would love to see one in the air.[sm=teeth_smile.gif][sm=thumbup.gif]

I almost went ahead and bought a Midi fan blade to have around and see if I could mount that up and test it, but it's an EDF blade and not quite sure it would be able to handle the pulses a single cylinder would put out without breaking.

I also have an AXOFLOW 049 ducted fan "kit' but the hub is drilled off center so badly it is not even usable without total rework of the hub. Plus it weighs more than it should with a very large aluminum core that has been molded around. But then again could provide good reference for impeller design. That one however is more suited to being checked on the CMM.

Many have tried to convince me to simply convert to EDF, but the greaser in me won't allow it. I love Cox engines and to me it just wouldn't have the right thrill. Backplated reed engines are still common and allow them to be mounted in reverse, which all of these except for the PeeWee powered Tiger use a pusher design, but a few left-handed crankshafts are still around to convert a TD if you wanted.

gcb

A few comments:

Do you suppose the electric unit would work if you inserted a small flywheel to smooth the pulses?

If using the reedie as a pusher, remember to add a steel washer behind the thrust plate.

Berkeley kits were noted for bad wood and great plans. In a discussion of a Berkeley kit was the first time I heard the term "die crunched". Apparently they often ran too many kits before sharpening the dies. Also it is hard to prevent crunching if you use the lighter balsa. All kit manufacturers were competing for the lowest prices so balsa quality/consistancy suffered. I don't remember griping about replacing some balsa, I just did it. I believe the kits would range from good to poor, depending on what the manufacturer had available at the time.

Planking: Cut your own strips at a slight angle so no gaps are left as you plank the round formers. A company made strips that were rounded concave on one side and convex on the other to hide gaps when planking. Don't remember which one. I think they gave up because it was costly and did not sell well.

George

jetpack

My Feedback: (1)

All good comments George,

The flywheel idea would help, and I suppose that was the theory behind putting in such a large slug in the AXO fan blade, but that seems to counteract the weight vs. power issue. The best flywheel is one that is light, but large as possible in outside diameter. The inside "circle" of the hub area is quite small because the blades start very early on diamter, but worth keeping in mind.

The optimum would be to have a ring that encircles the blade tips. That would require the least weight, but would be the hardest to achieve. What comes to mind is there used to be toy helicopters that I remember where the blades were not kept open, but kept enclosed within a molded ring. I think this not only kept the flimsy blades from breaking, but added to the inertia to keep it spinning longer. It had a two-fold function. Three if you counted in the gyroscopic stability.

That washer that you mentioned will help on power and wear, I have a few stainless steel shims on hand for that. Cox also had those fiber ones, but not sure what would rob the less power in a pusher. Another thing that those washers help with is keeping the end play out of the crankshaft when it's set up as a pusher. It helps keep the crankpin located better under the centerline of the piston.

If the crankshaft is allowed to move too far back you lose the squarness relationship between the crankpin and rod journal. Bad wear and breakage is soon to follow when that happens. Everything is dimensioned for that crankshaft to be pulled forward when in use. Learned that hard way when I was a kid playing around with my scratch built airboat. I had it free running circles and it just got saggy and more saggy till it just went clunk on me. My first broken motor.

For planking those fuselages, the bulkheads are not supported at all before planking. I guess the best approach is to lay the first plank right smack dab in the middle to act like a stringer and work out from there. The bullet nose and coke bottle shape on all these is going to be quite an act when it comes time to put down the "gore" strips (as Berkeley calls them).

They not only have to be beveled, they also have to be tapered end to end. Cutting them with a straight edge at an angle like you suggested would be a good jump on getting them sanded properly as they are fitted, instead of starting with a straight strip and sanding in all the angles. Especially with the contest grade balsa I'll be using. Thinner than your standard 1/16" also. It will be like trying to sand spaghetti without breaking. I might even pre-form it over a form using ammonia and water, and slitting it while it's on its form. Not sure. I almost have to enroll as a Cooper's apprentice.[sm=confused_smile.gif]

gcb

It would appear from the plans section showing the bulkheads, that the bulkheads are assembled, then an outline is laid out like a "keel" upon which the bulkheads are positioned vertically. You probably build the fuselage on a board in two halves, then join the halves. Not unlike some rubber models are built...Don't build two left sides! [8D]

Although by today's standards it is a tough build, it sure will sharpen your building skills.

You might want to review some rubber model books for suggestions for jigs, etc. There are some rather elaborate ones for holding those bulkheads if you so choose.

Good luck with them. You mentioned that you are taking your time with them so it should be an enjoyable experience.

George