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Old Jan 12, 2009, 06:49 PM
Bi-Planes
Tim Farrar's Avatar
Houston Texas
Joined Apr 2006
1,589 Posts
I hope you get your shaft problem worked out Dag !

I'm sure you will but I just thought I would say so anyway ...lol...

Great job Dag !!


Seeya, Tim
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Old Jan 12, 2009, 06:57 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,062 Posts
Quote:
Originally Posted by Tim Farrar
I hope you get your shaft problem worked out Dag !

I'm sure you will but I just thought I would say so anyway ...lol...

Great job Dag !!


Seeya, Tim
Thanks Tim, you rock my friend.
One way or another this plane will fly this spring. I just want a well designed power solution. I know wing structure can support the motors, I designed it to work if the shafting would not work. What is funny is the weight of these huge Lipo's really help with the CG, and the fact that I am going to have 11 A123 packs up front for ballast does not hurt. The plane with shafting would weigh about 66 pounds, without about 85.

One way or another she will fly .

DAG
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Old Jan 12, 2009, 07:16 PM
Registered User
RiBell's Avatar
Canada, BC, Abbotsford
Joined Jan 2003
4,801 Posts
Quote:
Originally Posted by dag214
I just want a well designed power solution.
The plane with shafting would weigh about 66 pounds, without about 85.

One way or another she will fly .

DAG
Dag:
That's 20lbs difference. For that reason alone I would stick with the shafting.
Some extra thoughts to ponder.
~OK first off 20 lbs is a lot of weight even for a monster this big.
~The carbon shafts seem like a lot of work. If it was all aluminum or stainless I would think that you should be able to install and forget about them.
~A shaft solution also solves prop mounting.
My $0.02
Rick
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Old Jan 12, 2009, 07:21 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
San Jose, CA
Joined Jan 2008
28,019 Posts
Hi Dag....

The other "solution" to the problem, is to put just a bit of loctite where the bearing meets the shaft, This will eliminate most chances for the bearing to spin on the shaft. Also...one thought, you could possibly use a set of the "dogbone" universal joints as used in 1/8 scale (or larger) RC off road cars. These things take a real beating, and I would think they would stand up to the stresses from this situation.

SteveT
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Old Jan 12, 2009, 07:46 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,062 Posts
Quote:
Originally Posted by RiBell
Dag:
That's 20lbs difference. For that reason alone I would stick with the shafting.
Some extra thoughts to ponder.
~OK first off 20 lbs is a lot of weight even for a monster this big.
~The carbon shafts seem like a lot of work. If it was all aluminum or stainless I would think that you should be able to install and forget about them.
~A shaft solution also solves prop mounting.
My $0.02
Rick
Thanks,
The shaft I am testing is the longest and is from the #4 nacelle, it is a aluminum shaft.
What I have to solve to keep the shafting idea.
1. At the rear where the prop attaches I seem to have a problem getting the 8m thread rod into the shaft true, I am getting better, but not perfect.
2. If the mid-bearing ever fails it is about a 2 hour job to get it out, and if the shaft is screwed up having the back-up shaft at hand.


That is not much to figure out, but if any of these happened at the field it would end my day of flying.

I am setting up my test cell for another round of testing with the bearing mounted better.

I will video up close what the bearing is doing.

Thanks, DAG
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Old Jan 12, 2009, 08:01 PM
Coy, peruser of worlds
gnats82's Avatar
Augusta, KS USA
Joined Dec 2007
4,871 Posts
dag -

I, too, would suggest the application of the appropriate Locktite at the bearing/shaft fit. Occasionally it was the only practical 'fix' for loose shaft/bearing fits on motorcycles and some lawn and garden equipment that I have serviced in the past, even under warranty, and it worked well.

Additionally, it might be that two bearings at the propeller end, set about an inch or so apart may be worth a try. I realize this will add a bit more weight but on the test cell, it wouldn't be too difficult to add and try. I recall someone posting a question about what was going to take the thrust loads but am not sure where you ended up with that.

I have been pondering these same issues with shaft drives that you are working on, mine a Northrop N9M which would be using IC motors. One thing I've considered is a kind of 'shock coupling' that would be mounted at the drive shaft/motor joint as a kind of harmonic balancer, as well as a light flywheel, which you would not need on electric. I've made no tests or any hardware, just paper and pencil and head scratching
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Old Jan 12, 2009, 08:25 PM
Übung macht den Meister..
Deuce's Avatar
United States, OR, Fairview
Joined Jul 2006
3,026 Posts
Can't remember if this has already been suggested, but what about something similar to the Flexidyne coupling Molt Taylor used in his pusher designs? Would that even be applicable to this setup?

Shorter shaft sections, and some means of dampening...

Just thinking out loud...

James
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Old Jan 12, 2009, 08:29 PM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
8,517 Posts
Quote:
Originally Posted by dag214
After a bunch of thinking and some true desire to make a great flying plane I may have to just admit that taking on shafting was to to much. Sure I can make it work, but I want to have a plane that has normal duty cycles. Check a nut here tighten a loose screw.

DAG
Dag,

I have a few suggestions...

> How about short shafts and mid-mounted motors?
> How about talking to the boat guys, they run long shafts on a regular basis?
> How about a flexible shaft solution, much like a dremel?
> Change to the A60 16M motor, rear mounted, 100 grams less and run it off 6S packs.
> Add more pack capacity, say 8,000 or 10,000 and use that extra LiPo weight to offset rather than dead (useless) counter weight...

Jack
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Old Jan 12, 2009, 08:36 PM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
8,517 Posts
Dag,

As to the centering issue, leave the shaft un-threaded, use an 8mm/10mm collet adapter. This would have the benefit of allowing you to machine one size shaft only (the longest) and when needed, simply cut it to size (length) and install...

Jack
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Old Jan 12, 2009, 09:03 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,062 Posts
Quote:
Originally Posted by jfetter
Dag,

As to the centering issue, leave the shaft un-threaded, use an 8mm/10mm collet adapter. This would have the benefit of allowing you to machine one size shaft only (the longest) and when needed, simply cut it to size (length) and install...

Jack
Thanks Jack,
How does the collet attach to my shaft , I mean do you have a sketch of how the collet mounts to the end of the tube??

Thanks, DAG
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Old Jan 12, 2009, 09:11 PM
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Hepdog's Avatar
Stonewall, MB, Can
Joined Jul 2004
2,875 Posts
Dag I'm glad you found that...before it failed. The balance issue does make running shafts very attractive - 20lbs of ballast

But high rpm drive shafts are a notoriously tricky thing to build. The other scary part is if you have a drive shaft failure in flight. Will you be able to keep power to the other motors while it flails about? Will that motor overamp itself and cause other problems

Should you consider a sheer pin or point somewhere near the motor so that at the very worse the motor could free spin. Washing machines use a 3 tooth dog bone type arrangement. 2 plastic dog bones connected via a floating rubber biscuit. Might help reduce transmission of vibrations.

OR just build it as you are and see what happens with lots of testing hours. If you use locktite as mentioned that might do it. Really what is the worst thing that could happen? How much thrust would 5 props give you? 4 props etc. What are the odds of 2 failing anyway....

I love complicated projects like this that push the boundaries. If it were easy everyone would be doing it.
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Old Jan 12, 2009, 09:25 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,062 Posts
All,
Sometimes I like to just set back and look at all of what is going on, or going wrong. When I look at my shaft design I believe it is sound, then when I look at the way I made it, I have to asked my self how good was my machining, really this is only the second shaft I have ever made that actually saw any power put to it. When I think about what I have learned I see where I could have improved it. I am going to really take some time tomorrow night and turn a new shaft, with better tolerances. If I make all the bearings fit the shaft correct, and I tap a true 8M thread, then there is no reason this won't work. I am sure in any design someone might turn 5 or 6 shafts before getting it right, but once I do, then I will know how to make the other 5.

And as far as losing a motor, they are all on their own set of ESC and batteries. And my calcs say she will fly fine on 4 motors, and hold altitude on 2.

Power is great, as long as you control it. A guy once told me freedom with out control is chaos.

Thanks, DAG
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Old Jan 12, 2009, 09:29 PM
The Hun in the Sun
vonJaerschky's Avatar
Canada, BC, Comox
Joined Nov 2003
7,474 Posts
I'm no expert on "shafting" and have certainly never undertaken a project as complex as yours, but I think you are on the right track in keeping it as simple as possible. You have 6 power systems to look after, and like you said you don't want to spend all your time in maintenance.
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Old Jan 12, 2009, 09:32 PM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
8,517 Posts
Quote:
Originally Posted by dag214
Thanks Jack,
How does the collet attach to my shaft , I mean do you have a sketch of how the collet mounts to the end of the tube??

Thanks, DAG
The collet has a tapered slant where the thrust washer fits over, the tigher the prop, the more pressure against the thrust washer which in turn squeezes the shaft even more.

Take a look at this picture. These are smaller adapters but you can see the slant on the shaft, the thrust washer has a reverse taper that slides over the slant and squeezes it closed. You can see the relief cuts in the shaft that allow it to be squeezed smaller. In your case you'd want the HD ones I originally pointed you to (8/10), 8mm hole for drive shaft, 10mm threaded shaft for prop. If you want to try one go here and select the 8/10. If you need measurements (length) let me know and I'll measure mine, I use the same ones.

If you are concerned about them coming off, don't be, I have 4 planes that fly on 12S, 2 have threaded shafts and 2 use collet adapters. I've never seen a failure and they are always trying to pull "off", yours will only push "on" even more since they are pushers...

Jack
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Old Jan 12, 2009, 10:00 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
San Jose, CA
Joined Jan 2008
28,019 Posts
Hi Dag...

I second what Jack has said about the collet adapters.

And if I may make some suggestions..

To start, if you have a collet set for your lathe, then of course use that to hold the shafting for machining. If you don`t have a collet set, though more tedious to set up, a four jaw chuck can be dialed in to run more true than a three jaw. If you only have a three jaw, and your shaft is not dialing in true before you start to drill it, try putting a very thin piece of shim stock in between one or two of your jaws.

#1.... If using solid shafting, when drilling the hole to insert the stub shaft, make sure you use a center bit, not a standard bit to start the hole, then use a stub length drill bit, as they are less flexible. If using tubing....start at #2.

#2...bore the hole with a boring bar type lathe bit, and leave slightly undersize.

#3...Ream to size.

#4... make a solid stub shaft to the size you need for the collet adapter. If you have a knurling tool knurl the end going into the shafting

#5...If you are using aluminun or steel shafting use red loctite instead of epoxy to fasten the stub shaft into the shafting. If using carbon fiber use JB weld, not epoxy, as most epoxies never "really" cure rigid.

As Jack said...the collet will never be able to pull off, as, as Jack stated, it will be pushing itself farther onto the shaft, not trying to pull off. You can also pust just a bit of blue loctite onto the shaft when you install the collet adapter.

Just a few thought....take them with a grain of salt, but I think they should work. As to the machining techniques, as I don`t know how much experience you have, you may already know these things, and if you do, sorry for telling you how to do them.

SteveT
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