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Old Oct 15, 2008, 03:15 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,724 Posts
Quote:
Originally Posted by appleflyer
so how far have you gotten on the B-36D? all ive seen for far are pics of the 3D animations.
I have plotted out all of the fuse bulkheads and trussing and hope to start cutting them out this weekend, my company comes before aviation and next week and I have to be traveling. I also hope that I get the #3 engine nacelle cut out this weekend as I want to get the mock-up of that built before I order all six motors. One reason I started this build thread so early is that when I started the thread on my Vintage 1919 everyone wanted to see how I designed it. My goal is to have all wood cut out by mid November. I hope to have the fuse framed up by November 1st week in November. I also had built and taken a part the left main gear which now will be built by Centry Jet Models.

Thanks, DAG
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Old Oct 15, 2008, 07:33 PM
Put a bigger motor on it!
gtfreeflyer's Avatar
Costa Mesa, CA
Joined Feb 2007
1,376 Posts
LOL! It would only be better if you had the neighbor's kid sitting in their Power Wheels next to this.

Do you do any stress analysis on these huge models or do you just design by "general rule of thumb"?
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Old Oct 16, 2008, 05:58 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,724 Posts
Quote:
Originally Posted by gtfreeflyer
LOL! It would only be better if you had the neighbor's kid sitting in their Power Wheels next to this.

Do you do any stress analysis on these huge models or do you just design by "general rule of thumb"?
My girl has a jeep, never thought of that picture but would have been really funny.

Most of structural analysis are "rule of thumb", the only place that I really look at the numbers are the landing gear, and wing, on my B-29 my landing gear ended up weighing over 9 pounds for all three of them, after going thinner wall aluminum, and using carbon fiber tubing for the strut arms I was able to get them down to 5 pounds. I also used carbon fiber rod as the axles. This planes wing is going to be my lightest design yet and I am going to build the truss spar and see what it can hold, then build the wing accordingly. I have found that most forces on a properly designed wing are just like loads on a bridge. In most cases you should only have loads in tensile (pulling), and not moment (bending). My built-up 55% Pitts S-1 top wing weighed 4.5 pounds, but could hold my sons weight at the time of 120 pounds. With this thick wing I have the luxury of being able to build a true truss structure as the wing spar.

Thanks, DAG
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Old Oct 16, 2008, 10:21 AM
Put a bigger motor on it!
gtfreeflyer's Avatar
Costa Mesa, CA
Joined Feb 2007
1,376 Posts
One more question...
Where do you store all these planes? Have you built a hanger yet
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Old Oct 16, 2008, 05:46 PM
Bi-Planes
Tim Farrar's Avatar
Houston Texas
Joined Apr 2006
1,589 Posts
Quote:
Originally Posted by gtfreeflyer
One more question...
Where do you store all these planes? Have you built a hanger yet
Wow !!
I never thought about it but that is a great question !!!

Where do you keep them Dag !!!!...lol lol lol...


Seeya, Tim
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Old Oct 16, 2008, 06:48 PM
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RiBell's Avatar
Canada, BC, Abbotsford
Joined Jan 2003
4,662 Posts
Quote:
Originally Posted by dag214
I have found that most forces on a properly designed wing are just like loads on a bridge. In most cases you should only have loads in tensile (pulling), and not moment (bending).
My understanding on structural designs is that the parts that are under compression need to be a little bit beefier as they will fail before the parts in tension.
There is a neat little game program called bridge builder. It's a little bit addicting, you have to build a train bridge, on a budget. You can do a stress analysis to see where it failed. Most failures are compression.
Yes I know its a little game, but it does seem to give a pretty accurate results or at least how I understand.
Anyway back to watching a B-36D
Rick
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Old Oct 16, 2008, 08:34 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,724 Posts
gtfreeflyer/Tim:
I keep most of my planes broken down in a room above my garage.

RiBell,
You are 110% correct, thing are stronger in tension, than compression. But what is a real bad idea is to design around bending forces.

I what to update you all on a conversation I had with Tom Hunt, he is really into electrics and has overloaded me with what works and what does not. Tom has been doing electrics since the 80Ēs and he is a real engineer at Northrop Grumman for almost 30 years. He said the reason belt drives have fallen of the earth is because they are just not efficient and other technologies have made them obsolete. Tom has given me plenty of direction on what will work, now I have to finish the re-design of the plane to see what size prop I really will be turning. In the end he said that be it geared or direct drive you still have to have the same load to turn it, its just at what weight the power plant needs to be. The out-runner with direct drive will still turn the prop I need, but the geared in-runner is half the weight. Steve Neu got back with me and is going to tell me which motor/gear box combo will turn my prop. So my plans are to build a mock up of my #3 nacelle and try the Axi direct drive, then the Neu geared and see which gives my the rpmís I need and also which one gives the best trade-offs for weight. The Neu motor may be light enough that I would not need to shaft drive,which would be great.

More rendering attached of my wing and fuse development.

Cutting out some wing ribs and bulkheads tomorrow.

Thanks all.

DAG
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Last edited by dag214; Oct 16, 2008 at 09:23 PM.
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Old Oct 16, 2008, 08:46 PM
Bi-Planes
Tim Farrar's Avatar
Houston Texas
Joined Apr 2006
1,589 Posts
Great Dag !!

I'm glad you are getting somewhere now with your motors, I know that has been bothering you !!!

I'm really glad you started your build thread now for us so we can see how you do this with your drawings...

I appreciate you doing this, it is very interesting to keep up with.
Even when I dont post I am here reading...lol lol lol...


Seeya, Tim
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Old Oct 17, 2008, 06:13 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,724 Posts
Quote:
Originally Posted by Tim Farrar
Great Dag !!

I'm glad you are getting somewhere now with your motors, I know that has been bothering you !!!

I'm really glad you started your build thread now for us so we can see how you do this with your drawings...

I appreciate you doing this, it is very interesting to keep up with.
Even when I dont post I am here reading...lol lol lol...


Seeya, Tim
Thanks Tim,
I have always had the feeling that you were there lurking in the shadows. This motor thing has been a big deal. In designing something where every once is scrutinized is what makes this so hard. If I use a out-runner I need 2 wing tubes so that I can have a clear path for the shafting to the props, if I use a geared in-runner it may be light enough to leave it at the rear on the nacelle, this would save on having 2 wing tubes and that associated weight, but any ounce behind the CG needs ballast in the nose. If I have time I am going to re-calculate this weekend what the geared in-runner weight saving will be, but I took today off to try to get set up to start cutting some wood, I may cut some ribs to day but not the wing tube holes as I may go back to a single wing tube design.

And thanks for all your support, my b-29 never had a thread and everyone that saw it didnít know that it was a Don Smith plan drawn in 3D so that I could re-design it as an electric, everyone wanted to see pics and itís progress, but in the end it was scraped because it called for a wing design that had the bottom main spar cut out to allow the landing gear a place to go in. In the end the wing was to light to take flying loads and just didnít work, a year of work down the tubes. The whole airframe only weight 11 pounds and had a 181" wing. Completed my weight was 36 pounds

Thanks, DAG
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Old Oct 17, 2008, 07:55 AM
Bi-Planes
Tim Farrar's Avatar
Houston Texas
Joined Apr 2006
1,589 Posts
Oh Man !!

I cant imagin all that work for nothing !!!

It sure looked great though from those pictures !!!

I mean it really looked nice !!!

I know it is spilled milk now but if you still have it you should some day try shuving a aluminum tube or a carbon fiber tube down that wing.

I guess there isnt enough room though or something like that because I know you wouldnt have scrapped it if there was something that could have been done.

11 lbs at the stage you had it is really great too !!!

Well, I suppose it may have served a purpose for this one...I bet you have that spar problem in mind this whole build until this wing is finnished...lol...

For real though, I hate that you had to scrap such a nice job and so far in the making...
It is sad to me...


Seeya, Tim
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Old Oct 17, 2008, 08:52 AM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
8,110 Posts
Quote:
Originally Posted by dag214
Welllll,
After thinking more about what Tex said about shafting the motors I think it is 110% the way to go.

Thanks, DAG
Awesome project, will be watching with great interest!

I do have an alternate suggestion to the shaft idea, that is use the LiPo's for ballast. I imagine you will want them in the nacelles anyway (or in this case, a pocket in the front of the wing in line with each nacelle) to reduce the wing joint stress at the fuse...

Jack
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Old Oct 17, 2008, 10:05 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,724 Posts
Tim,
All that work showed me how to use my mill and lathe , and all that work helped me to understand how important it is to make sure it fits in 3D, because if it don't it won't when you cut it out. It was a set back, but I never would have taken this on this project with out knowing what I do now.

jfetter,
My batteries are at the leading edge already in this design, at first I was going to put them in the nose, and then I learned that the battery should not be more than 18" from the speed controller, the in-rush of current stored in the long wire run can blow out the speed controller, that was a huge set back, but I think I have it under control now, at least I hope so.

Thanks all,

DAG
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Old Oct 17, 2008, 10:19 AM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
8,110 Posts
Quote:
Originally Posted by dag214
jfetter,
My batteries are at the leading edge already in this design, at first I was going to put them in the nose, and then I learned that the battery should not be more than 18" from the speed controller, the in-rush of current stored in the long wire run can blow out the speed controller, that was a huge set back, but I think I have it under control now, at least I hope so.

Thanks all,

DAG
DAG,

You are correct about the Battery-to-ESC leads BUT you can extend the ESC-to-Motor leads considerably. I've extended them 36" in pushers before without issue (make sure they are even) and I've heard others that have extended them more...

Jack
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Old Oct 17, 2008, 10:41 AM
Bi-Planes
Tim Farrar's Avatar
Houston Texas
Joined Apr 2006
1,589 Posts
Quote:
Originally Posted by jfetter
DAG,

You are correct about the Battery-to-ESC leads BUT you can extend the ESC-to-Motor leads considerably. I've extended them 36" in pushers before without issue (make sure they are even) and I've heard others that have extended them more...

Jack
Wow, I hate to put something else on your plate to think about but that does sound like something to look into Dag.


Seeya, Tim
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Old Oct 17, 2008, 12:06 PM
Vintage Flyer
Indiana
Joined Jan 2005
1,674 Posts
Hey Dag,
You ever get an uneasy feeling that Homeland Security may come knocking on your door in relation to the "large scale" Air Force you're building???
LOL!!!!

Ed
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