Sheet Metal Engine Mount?

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Bigshu

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The Hummel H5 and the UC both Bed mount I believe. I attached th eH5 pictures I got from the factory.

Matt
Pics are worth a thousand words! I've got a pic somewhere of the H5 that I saw with a welded mount. If I find them, I'll post, but the engine box design on the H5 is very easy to fabricate.
 

103

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I agree I wonder if a Sheet Metal mount could be used on a 4130 Tube Fuselage or Wood fuselage like the SSSC.

Flywheel Drive VW are more conducive to bed mounting.

Matt
 

Bigshu

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It seems like the box has plates thst tie back behind the firewall, into the front fuse structure. Not sure if it would translate to tube or wood. I guess the trusses could be bolted or screwed to a plywood fuse structure in back of the firewall...rather than riveted. Anything that replaces welding is ok in my book!
 

12notes

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Well, my H5 plan set from 2008, on sheet 2 clearly details the engine box (bed mount) for the full size VW engine. Another well known Hummel builder who's local to me, did use a welded mount, but the built in bed mount is clearly what Hummel has in mind for the H5.
Well ****, I've only seen conventional mount H5s, and bed mounts on the Ultracruiser, guess I just assumed the H5 plans were like the Hummelbird I'm building.

I'm obviously wrong about the H5, sorry for the confusion. I'll update my original post to reflect that.
 

Bigshu

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No problem, I had to take a look to make sure the H5 plans are like I thought! Dennis Brooks, the builder I mentioned earlier, has a nice H5, to go with his Ultracruiser (or is it a Hummelbird?). He's built two nice airplanes, and I can't wait to see his H5 after it gets painted. You can follow his aircraft on you tube, he's got tons of videos.
 

pfarber

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I don't think a sheet metal monoque mount would be as good an option as a tube steel or cradle mount.

First would be that you would need a lot of of fairly thick metal, and it would act as an amplifier for engine noise.
Second would be access to the rear of the engine.

By the time you put in strengtheners and access holes you'd have the traditional tube steel mount.
 

Bigshu

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The Hummel engine mounts are pretty simple and light. I call them bed mounts, but they might be what you consider a cradle mount.
 

Tiger Tim

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I don't think a sheet metal monoque mount would be as good an option as a tube steel or cradle mount.
Generally I agree with you completely. I started the thread because I’m very slowly thinking my way through how I would build a maybe-UL-but-probably-LSA replica Buhl Pup and the original airplane’s fuselage was just one big tin can from engine mount to fin post. I still think there are definitely ways to do it, it just sounds like ai won’t get the benefit of copying someone else’s homework.

Good point on it being a big megaphone for the engine though, I hadn’t considered that.
 

Bigshu

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Whether the engine bolts directly to a fuselage bed mount, or bolts to the firewall on a welded tube mount, it's still sitting in the sheet metal megaphone. I don't think I've ever heard the argument that engine noise is more of an issue in a metal airframe with a bed mounted engine.
Talk to the folks at Hummel about how they designed the bed mount for their designs, and any thoughts on excessive noise from having the fuselage support the engine rather than direct connection to the firewall. I'd think input from an aircraft manufacturer would be more definitive than a builder's opinion (mine included).
 

miket402

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the engine mounts to the main angle attached to the firewall. the engine does not mount to the sheet metal. the t6 angle carries the load of the engine. Of the four angles, two act as side rails and run level from the firewall back past bulkhead C (where the pilot sits) up to D I believe. the two engine mounts on the bottom use two t6 angle that extends from the firewall back to the T.E. of the wing under the pilot's rear. The hardpoints on the H5 are at the angle where they join with the horizontal angle attached on the firewall. The hardpoints use A.N. bolts and whatever frame is being used for your engine. I am in the process of building my H5 now and I was very confused about this point. I have since cleared up this by reviewing the plans and keeping at it. So basically the engine is mounted to two rectangles with the back end open. the sheet metal of the firewall, skins, and bulkheads (formers) actually attach to the framing. I count well over 100 rivets attached to all the framing (angle) and since I don't have pictures the angle that runs from the firewall to the aft of the fuse is approximately six feet times 2 and eight feet times 2. I sure hope this helps in some way. the BK that is packaged up and sold at A/S is a knockoff of one of the earlier hummel airplanes. Looking at some of the old Army and Navy videos about proper sheet metal uses I find many of the techniques used in those videos are used in the Hummel H5. Take care and I hope this helps those that don't quite understand the Hummel H5. My plans show the four mounting holes that look to be engine mounting as alignment for the front of the nose area with no engine. As a scratch-built, I have the option to mount my engine any way I want. I will be doing it as Dennis Brooks has and that is with a 4130 tube frame attached as it is shown on the plans I own.
 
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Jay Kempf

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If you design a cone of thin sheet metal you have to look at fatigue and buckling closely. Sheet metal is good at shear loads. Not good at buckling by itself.
 

Riggerrob

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Even the gentle curves of a Bulldog fuselage will stiffen skins and reduce "oil-canning."
A friend flies his Zenith 601 up to 600 hours per year. After a few years, he had to replace flat skins on the aft fuselage because of fatigue, smoking rivets, cracks, etc.
 

wsimpso1

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A sheet metal structure extending forward to the engine looks efficient weight wise, and probably is if you really have the design and engine position nailed. But if you are playing with how much offset up or to one side, well, it is a heck of a lot easier to fab a new tube mount with an adjustment.

Then there is the little issue of access to the top, bottom, and back (assuming conventional engine placement) to service the fuel pump, fuel metering, induction, exhaust, starter, alternator, vacuum pump, elastic engine mounts,, etc. With a steel tube mount and some thinking, the engine only has to come off the mount to split the cases. With monocoque, well, you had better think ahead...
 

Pops

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Hard to beat a steel tube engine mount. Quick and easy to build, light weight, easy to repair and good access to the engine. The engine mount is the last thing I build. Do a W&B and work out the length of mount to put the CG where I want.
Engine mount I built for a Cont on my Zenith. Engine case hanging on the mount for nose weight.
 

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Bigshu

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the engine mounts to the main angle attached to the firewall. the engine does not mount to the sheet metal. the t6 angle carries the load of the engine. Of the four angles, two act as side rails and run level from the firewall back past bulkhead C (where the pilot sits) up to D I believe. the two engine mounts on the bottom use two t6 angle that extends from the firewall back to the T.E. of the wing under the pilot's rear... As a scratch-built, I have the option to mount my engine any way I want. I will be doing it as Dennis Brooks has and that is with a 4130 tube frame attached as it is shown on the plans I own.
Dennis is a great resource for all things Hummel. But, so is Terry, and whoever took over the operation recently. I'm not sure your assessment is accurate. While the engine attaches directly to the angle pieces, I think a significant amount of the load bearing capacity is in the skins and doublers. I'd check this point directly with the folks at Hummel if I were you. You could prove the point to yourself by mounting the angles to the firewall and then mounting the engine, leaving the skins and doublers off completely in the engine area and see what happens. The number of rivets is the first clue. You don't need anywhere near that many to attach skins unless they are considered structural. Have you started a build thread yet? I'd be very interested, since I'm working on an H5 build myself. Take care!
 
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