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  1. #1

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    Dummy radial engines:

    I need to cobble together a radial engine for a 1/4 scale Curtiss Goshawk (picture attached). I needs to be about 13 inches in diameter. Is there anything out there that I don't know about. The biggest I have been able to find is considerably smaller.

    Thanks,

    Bish
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  2. #2
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    RE: Dummy radial engines:

    Williams Bros Co. has released the 1/4 scale radial cylinders and crankcase and there are Vac formed radial engines that can be bought. I work for a hobby shop and I will get you the info on the vac formed products tommorow if you are interested. Nice aircraft by the way I've seen it before on another thread.

  3. #3

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    RE: Dummy radial engines:

    try a Williams Bros P&W Wasp in 1/4 scale. It should finish at 11-3/4" in dia.

  4. #4
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    RE: Dummy radial engines:

    The vacuumed formed dummy engines that feep mentioned can be made to look very convincing with little effort. If you're not going into competition, these could be a convenient alternative for you. I've used two of them, one in a Top Flite P-47 and most recently in a Dave Platt Bucker Jungmeister. Just my dos centavos.

    Al

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    To wives and sweethearts. May they never meet.

  5. #5

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    RE: Dummy radial engines:

    Thanks gents,

    I have used a vacuum formed engine from Zirolli (pic attached) and it came out pretty O.K., but I need a bigger one. As I said, the diameter I am working with is 13". As a last resort I have thought of attaching the individual cylinders to an enlarged crankcase to get the proper diameter. If I can't find a better way to do it, enlarging the crankcase will work, but it won't look quite right. So if any one has more ideas, you have my attention.

    Thanks,

    Bish
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  6. #6
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    RE: Dummy radial engines:

    Frank Tiano sells resin cast Pratt dummy engines but his largest is 11.5" (1/4 scale). Still it might be worth giving him a call to see if he has a solution.

    http://www.franktiano.com/scaleproductFrameset.htm
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  7. #7
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    RE: Dummy radial engines:

    So Bish, I don't understand. If it's a 1/4 scale Goshawk why do you need a radial that works out to be larger than 1/4 scale. What engine did the aircraft use?

  8. #8

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    RE: Dummy radial engines:

    Feep,

    I see your point, but the plane used a Wright Cyclone R1820. I think that is the same engine the B-17 used, but anyway it is a whole lot bigger than the engine the Williams Bros offer. Williams bros is a 1/4 scale model of the P&W 985. The numbers, 1840 and 985 represent the cubic inch displacement of the engines. So the Goshawk engine was twice the diplacement of the P&W 985.

    Bish

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    RE: Dummy radial engines:

    Check with Craig at Fiberglass Specialties, 479-359-2429. He has been very helpful with me. I just got a fiberglass Radial engine for my Top Flite Giant Corsair. He has large dummy engines. I know he makes fiberglass cowling's up to 20" in diameter. So he must make a big enough dummy radial for that.

    Try him,

    Gibbs
    Barry - Owner of Canopy Rails For Warbirds

  10. #10

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    RE: Dummy radial engines:

    Good idea "probie"! He made the cowl for this plane a few years ago, so he may well have something. Thanks.

    Bish

  11. #11

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    RE: Dummy radial engines:


    ORIGINAL: Bish Wheeler

    Feep,

    I see your point, but the plane used a Wright Cyclone R1820. I think that is the same engine the B-17 used, but anyway it is a whole lot bigger than the engine the Williams Bros offer. Williams bros is a 1/4 scale model of the P&W 985. The numbers, 1840 and 985 represent the cubic inch displacement of the engines. So the Goshawk engine was twice the diplacement of the P&W 985.

    Bish
    Would that be because the R-1820 is a twin-row (18 cyl) and the 980 is a single row (9 cyl) engine? Either way, the diameter of the engine at the valve covers would be the same. There may also be a slight out -of-scale condition in your model where it is slightly larger than 1/4 scale, making the cowl diameter not match the available dummies.
    Club Saito #2, WACO Brotherhood #20. What other trouble can I get into?

  12. #12

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    RE: Dummy radial engines:

    Good point, but the 1820 is a single row, 9 cylinder engine. The Goshawk is from Barron plans which were exact and it is spot on quarter scale. The 1820 is just a bigger engine. I have smithsonian drawings of the bird showing the engine. If I had a "Mini Lathe" I would simply turn cylinders (and fins which is the real challenge) and make a dummy engine of the correct size out of plastic pipe stock. I ran the cost of a lathe ($700 +/-) by my wife and bless her she thought that was not too bad, but "maybe in the spring" after we do all the other things she has planned!!

    I may contest with this bird and if I do I will have to have a dummy engine in it. To tell the truth I just want to have one and I enjoy trying to figure out how to do it. Going to give a call to Craig at Fiber Glass Specialties and see what they offer or if they have a referral.

    Thanks guys,

    Bish

  13. #13
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    RE: Dummy radial engines:

    Bish: If you decide to do your own, you should examine this. Be sure to look at the "How To"s.

    http://www.alumilite.com/ I have only played so far, but I like it.

    You would have to make only 1 perfect cylinder, then cast the rest. I have planned on doing this for a Kinner, one of these days.

    I have a Sherline lathe, but I thought I could get better results using chassis punches of two different sizes, punch the fins out of .010 styrene, then glue them to a tube of the appropriate size. The top end would have to be carved out of something, but one might cast a block of Alumilite to the appropriate shape, then hand carve the fins.

    Les

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  14. #14
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    RE: Dummy radial engines:

    After due consideration, I think the chassis punch will cause too much distortion; perhaps hole saws of the appropriate size might be better. Cut the large diameter first, then using the same pilot, cut the smaller diameter, leaving the ring.

    Les

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    RE: Dummy radial engines:

    Here is a picture of my Fiberglass Specialties Dummy Radial for my Giant Corsair just after cutting it out. I will post some more pictures after I paint it and get the push-rod tubes and plug wires on it. I am putting an 1/8" x 10" circle of plywood on the back and putting in baffle holes for cooling. This way I can epoxy it into place and it will be much stronger. It is strong now but that will really beef it up.

    Probie
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  16. #16

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    RE: Dummy radial engines:


    ORIGINAL: Bish Wheeler

    I need to cobble together a radial engine for a 1/4 scale Curtiss Goshawk (picture attached). I needs to be about 13 inches in diameter. Is there anything out there that I don't know about. The biggest I have been able to find is considerably smaller.

    Thanks,

    Bish
    I did some reading after thinking about this, it was interesting to me as I am also into precise scale and want things to look "right". This is what I came up with:

    P&W had three basic 9 cyl single row engines-

    1-the Wasp Jr, at 985 c.i. and a diameter of 46.75 inches (comes out to about 11.7 inches in 1/4 scale)
    2- the Wasp, at 1344 c.i. and a diameter of 51.375 inches (about 12.9 inches in 1/4 scale)
    3- the Hornet, at 1690 c.i. and a diameter of 54.375 inches (about 13.6 inches in 1/4 scale)

    They all had both geared and direct drive versions, the geared ones being about 300 pounds heavier than the direct drives, but with more horsepower.

    the B-17 used Wright Cyclone engines, the single row 9 cylinder model R-1820.

    I guess when Wms Bros and others make their scale dummy engines, they use a generic looking engine, or just chose one or the other models to go by, hence the disparity in the size you have found vs. the size you need for your model.
    Club Saito #2, WACO Brotherhood #20. What other trouble can I get into?

  17. #17

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    RE: Dummy radial engines:

    Les.. With your lathe you can cut cylinder rings of styrene, enough for the fins and then slide them on a tube of the correct size. Then carve the top from balsa and glue it on. Then cast the entire affair using alumilite. I use the stuff constantly and it works very well. (For the styrene rings you need to use a flat plate mounted in your jaws larger than the rings. They make a special wax for mounting flat stock so you can turn out work from thin stock.)
    BobH.

  18. #18
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    RE: Dummy radial engines:

    Hey Bob.

    If I recall, you at least did the Hispano Suiza exhaust flanges out of that stuff.

    What I usually use for thin stock is double sided sticky tape (not the padded kind), but the machining operation is a bit more complex than I would like. I am not certain that I could get the repeatability that I would like. I have had an offer (from one who shall remain nameless unless he chooses to reveal himself) to laser cut the styrene for me. I find that much more attractive. All I have to do is draw them up the way I want them to turn out.

    The top end is a nightmare of horizontal, vertical, and diagonal fins. I don't think I would get satisfactory resolution out of balsa, and a mold may have to be 2 piece to even work.

    Les

    ps. we'll try that picture again
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  19. #19

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    RE: Dummy radial engines:

    Les, you are right. I made my flanges out of alumilite plus a lot of other things. I find that when I need several duplicat parts it's easier to make a mold and then cast them. The cylinder ring need only be one. Then you could cast that and then assemble and recast the entire affair. The top is a mess I will agree!. Lots of carving to get it right. If you can get a laser cutter to mass produce that's good too!

    Fyi there are several cast parts on this instrument panel I made for my 1/4 Camel.

    Some thing else I learned along the way is that you can paint the mold and then cast it immediately after. Your part will be painted in the mold and finished when you pop it out.
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    BobH.

  20. #20
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    RE: Dummy radial engines:

    Bob are you serious about the paint? I've been casting for 10 or more years and never would have thought that possible> I use a 2 part resin and it produces heat depending on the volume.
    ORIGINAL: BobH

    Les, you are right. I made my flanges out of alumilite plus a lot of other things. I find that when I need several duplicat parts it's easier to make a mold and then cast them. The cylinder ring need only be one. Then you could cast that and then assemble and recast the entire affair. The top is a mess I will agree!. Lots of carving to get it right. If you can get a laser cutter to mass produce that's good too!

    Fyi there are several cast parts on this instrument panel I made for my 1/4 Camel.

    Some thing else I learned along the way is that you can paint the mold and then cast it immediately after. Your part will be painted in the mold and finished when you pop it out.

  21. #21

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    RE: Dummy radial engines:

    Feep yep I'm serious.. The alumilite is a two part resin too. Both parts mix equally and do produce some heat. The Mags (Brass colored domes) were both painted in the mold first. I didn't even know about this process until one of the guys at my local HS told me about it. I was as surprised as any one..!
    BobH.

  22. #22
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    RE: Dummy radial engines:

    Hey Bob. I could make and cast 1 cylinder ring, but I am at 1/7th scale and the fins are only .015 thick. I think I would not even begin to handle them without breakage.

    Les


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