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Author Topic: B-17 F  (Read 8785 times)
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Bredehoft
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« Reply #25 on: March 16, 2017, 06:47:51 AM »

Back in 1966, there was an article by Dennis Norman on how he built and flew a DeHavilland Mosquito.  It was smallish and the secret was a belt drive.  It is worth a read if you are interested in belt drives.  Here is a link to an online copy of the article and plan.

https://volarlibremente.wordpress.com/2011/01/05/mosquito-iv/

--george
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Don McLellan
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« Reply #26 on: March 16, 2017, 04:12:08 PM »

Great story Tom!!  Love to hear stuff like that.

Crabby, I plan to have two CW and two CCW props, and will wind them from the wing TE.  I'm a little worried about the props smacking into each other, so most likely will glue the nose buttons to the front of the nacelles.

Added the second nacelle to the wing and couldn't resist pinning everything together.
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Sky9pilot
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« Reply #27 on: March 16, 2017, 09:13:06 PM »

I love the B-17 Don...coming along nicely. 
Tom...great story and didn't someone build the Northrup flying wing XB-35 or the YB-49?  I'd love to see one of these flying.
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tom arnold
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« Reply #28 on: March 16, 2017, 10:50:12 PM »

Yes, it was a much younger (weren't we all) Vance Gilbert and he powered it with a single big prop at the tail end of that center pod at the back. The motor ran the length of the root rib to the nose. It flew fantastic---really cool turning and dipping in the air--- and he had a construction article in Max Fax, the newsletter of the Maxecuters. I saw it fly a couple of times and in talking to him, he said the only hard part was the launching with no fuselage to grab.
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Ray_K
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« Reply #29 on: March 17, 2017, 09:51:08 PM »

3-17-2017

Wow, I seemed to have started something with the idea of using a pulley and belt drive system, the system has merit, I had built a Wright flyer using a pulley and belt system as a test and it worked quite well, for the B-17 it would be easy, the pulleys for the props would go directly behind the props not in the engine nacelles, and a double pulley would be within the fuselage to drive the props, only an access hatch would be required to get to the pulley within the fuselage to change belts if needed. FYI.

Cheers, Ray K. 
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ZK-AUD
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« Reply #30 on: March 18, 2017, 12:37:11 AM »

I'm starting to like this train of thought - what if the main drive double pulley in side the fuselage was actually a tube (with the grooved or notched section glued around it) rotating in a cradle which allowed the rubber to go the full length of the fuselage and through the tube.  After winding the nose plug would be attached and engage in the front of the tube.  The scale nose would be detachable to allow access for this.
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strat-o
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« Reply #31 on: March 18, 2017, 10:44:56 AM »

 I see what you are saying.  You actually wouldn't need a full length tube, just have it run from nose to mid-wing chord.  That should reduce complexity somewhat and reduce weight near the tail.
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rgroener
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« Reply #32 on: March 21, 2017, 05:35:24 AM »

Don, so cool!
That's a terrific project!

Roman
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Prosper
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« Reply #33 on: March 21, 2017, 07:42:08 AM »

Very nice, Don! I kind of hope you stick with the independent motors. All this central-drive stuff is very interesting but it seems to me that even if you made all the rotating stuff like a Swiss watch, the power losses would be huge and the weight gain considerable. I'd love to see you (or anyone) bung all that stuff into a 26" span model and see it fly like it meant it, but I'm a bit doobious. The Mosquito article George links to seemed worth a look but it states that the model can fly up to 40yds in a straight line. I'm not saying I could spit that far, but. . .we-ell. . .

I made a breadboard pulley setup - single pulley for a single prop - for a Supermarine Sea Otter idea I had. That showed real promise but the factors making it so seemed to me unique or almost unique to the Sea Otter.

Anyway, I'm enjoying the build and the discussion!

Stephen.
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Rich Moore
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« Reply #34 on: March 21, 2017, 03:13:49 PM »

I have yet to see a model fly well on indirect drive. I'm sure it has been done, but I haven't seen it. I've played with it myself, but not with any real success. (It is fun though, if you like that sort of thing). I have, however, seen many multies (with tiny nacelles) fly really well with direct drive...
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strat-o
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« Reply #35 on: March 21, 2017, 03:24:08 PM »

I believe that a successful indirect drive is feasible.  I built a Gollywock once and it flew with 20g+ of rubber.  It's launch was so fast that it was almost like watching a power model.  With the right combinations and engineering it is possible to create a high-performance indirect drive.
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billdennis747
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« Reply #36 on: March 21, 2017, 04:01:17 PM »

I always pictured indirect drive models being designed - maybe even built - during the blackout in WW2 England, as intellectual exercises. I've never seen one actually moving.
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glidermaster
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« Reply #37 on: March 21, 2017, 07:41:08 PM »

Wasn't the late Doug McHard successful with a twin of some description that used the Rupert Moore transmission system?

JB
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« Reply #38 on: March 21, 2017, 09:05:19 PM »

3-21-2017

If I am not mistaken wasn't the Moore drive a series of wires that transferred power at 90 degree angles ?

Cheers, Ray K.
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Ray_K
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« Reply #39 on: March 21, 2017, 09:10:03 PM »

3-21-2017

Something like this, this was in my R6 helicopter.

Cheers, Ray K.
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billdennis747
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« Reply #40 on: March 22, 2017, 03:40:28 AM »

Yes, it was just like that. Over the last 60 years there may have been a couple of examples of models with the Moore drive, but they weren't flying shots. The combination of weight + mechanical losses + poor rubber would surely have been insurmountable. I don't remember Doug McHard doing one but if anyone would have got it to work, he could. A few years ago he did an article on one of the vintage kits that interested him - Skyleada Vickers Viking? - but I can't remember how it was driven. We have seen so many successful direct drive twins (including the Viking)
Just before the late Mike Hetherington died, we saw his Moore(?) Bristol Blenheim (?) ready for covering. He was enthusiastic about the prospects; we were less-so.
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ffscale
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« Reply #41 on: March 22, 2017, 06:04:47 AM »

The Viking that Doug built was the Astral design, which had the rear motor hook in the fuselage just behind the wing trailing edge.  The motors angled out to the nacelles through the wing centre section.  The prop shafts had a wound spring on the back of them with a hook on the end to get the drive round the corner - possible because the angle is only around 45 degrees or so.  Doug wrote it up for Aeromodeller - I have a pdf of part two of the article (which deals with building and flying the thing) if anybody is interested.  It certainly comes across as a challenging project!

Mike S.
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Pete Fardell
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« Reply #42 on: March 22, 2017, 09:27:08 AM »

This one worked well by all accounts, although it was a light foamy...

A bit from Terry Adams, its designer, here:
https://www.rcgroups.com/forums/showthread.php?295267-Shaft-Drive-rubber-power-Bristol-Freighter

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FFScott
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« Reply #43 on: March 22, 2017, 01:25:47 PM »

Did he ever build the PBY he mentioned in the postings?
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vintagemike
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« Reply #44 on: March 22, 2017, 02:23:13 PM »

Doug also built the Short Scion, a C Rupert Moore design in the late 80,s, I seem to remember it flying at Old Warden, apparently there was plenty of power available through the Moore drive, but it was prone to lock up as turns ran out. 
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Pete Fardell
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« Reply #45 on: March 22, 2017, 04:09:12 PM »

Did he ever build the PBY he mentioned in the postings?
I don't know- I never saw the actual model and don't know the chap. I just remembered seeing it in Aeromodeller.
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Ray_K
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« Reply #46 on: March 22, 2017, 05:48:11 PM »

3-22-2017

My Moore drive worked ok but was a bit clunky.

Sorry Don for getting off track on your post, where are you at on the B-17? Looking forward to seeing more.

Cheers, Ray K.
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Don McLellan
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« Reply #47 on: March 27, 2017, 05:08:02 PM »

Decided to redo the wings with slightly larger diameter nacelles.  Also wing ribs 2 and 4 now have the nacelle upper member included as part of the rib.
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Ray_K
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« Reply #48 on: March 27, 2017, 06:56:34 PM »

3-27-2017

Don, she sure is looking good  Smiley, what's the wing span?

Cheers, Ray K.
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ZK-AUD
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« Reply #49 on: March 27, 2017, 08:44:24 PM »

Don that's looking great.  Just an errant thought I had - if the main spar was split at the engine nacelle positions and joined with say 2mm x 0.5mm carbon flat section top and bottom at those points you could run the rubber through the spar and further back into the wing.  Access for the rear pegs from under the wing...

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