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Old Yesterday, 01:54 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,671 Posts
Tailwheel thingamajig

Robert - certainly not for me to comment as I've never had a castoring tailwheel. Plenty of fixed skids - with no problems so maybe a wheel that is self-centring with springs?
I spent the afternoon making a simple brass tailwheel strut - it would suffice as it hides under the tailplane anyway but I wanted something a little more realistic and having a huge chunk of 1/2" thick aluminium, decided to hack one out from solid. It wasn't that difficult - just tedious. The holes that needed to be accurate (axle and steering shaft) were drilled when things were still square and tapped holes for a pair of 4-40 screws as well, Then it was hacked, filed, and sworn at until only a horse-shoe looking wheel 'stirrup' was left. Still a bit of work to do but surprisingly, the brass stirrup and collar weighs 5 gms. The bulky aluminium one with two grub screws is 6 gms! A bit more shaping and they'd be the same - and I know which one will look best
BTW - what is this thing called - trunnion? stirrup? bracket?...........?
Pat
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Old Yesterday, 01:56 AM
Balsa Lover
gupi's Avatar
Vienna, Austria
Joined Jul 2010
750 Posts
Depending on your RC equipment you could add a separate small servo on a free channel to drive your tail wheel and just mix it to the regular rudder.

The tail wheel bracket looks spectacular! I thought you've bought it until i read the text. The weight probably explains the success of aluminum in airplane construction.
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Old Yesterday, 02:01 AM
Balsa&Tissue
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United States, OR, Beaverton
Joined Jan 2011
2,409 Posts
Quote:
Originally Posted by gupi View Post
Depending on your RC equipment you could add a separate small servo on a free channel to drive your tail wheel and just mix it to the regular rudder.
I did this recently on two projects and it has the advantage of having separate trim for tailwheel and rudder as well as separate rates. Makes it much easier to adjust tracking vs. rudder trim. If you have enough channels it is the way to go instead of fiddling with a grub screw over and over till it tracks straight.

Dave
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Old Yesterday, 02:07 AM
Scale Builder
United States, AZ, Litchfield Park
Joined Jul 2002
2,466 Posts
Quote:
Originally Posted by Pat Lynch View Post
BTW - what is this thing called - trunnion? stirrup? bracket?...........?
I've always heard it referred to as a tailwheel yoke or, less often, a tailwheel fork. Whatever you want to call it yours looks fantastic.
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Old Yesterday, 02:33 AM
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shoey's Avatar
Australia, SA, Adelaide
Joined Jan 2009
676 Posts
Far out Pat! That looks awesome! Can you tell me what tools you used to make the fork? Was it all by hand? Just wondering if that is beyond my capability to do something like that...
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Old Yesterday, 03:24 AM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,671 Posts
I'm sorry - I didn't take any photos making the yoke but basically, the desired shape was marked out on a slab of aluminium, the axle hole was marked and drilled and then the centre area cut away using a string of 1/8 holes, breaking away the centre and filing to shape. The yoke was then cut away with a hacksaw and the outside filed to shape. The holes for the steering shaft drilled, and the 4-40 tapped holes drilled. The rest is just patient filing and tidying up - a work in progress!
Really, a sturdy vice, hacksaw and files are essential. A drill press is handy and a rotary sanding drum in a Dremel helps too.

The wheel is a larger lightweight foam tyre that was sanded 1/2" smaller in diameter.

Steering? I'm rather liking the idea of a separate small servo linked to the rudder.....food for thought!
Pat
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Old Yesterday, 04:40 AM
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shoey's Avatar
Australia, SA, Adelaide
Joined Jan 2009
676 Posts
Thanks Pat, that may be doable even for me! I've just ordered an electronic copy of the wirraway maintenance manual so hopefully it should have some good technical drawings of the tail wheel and main gear.
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Old Yesterday, 08:10 AM
Parkcityflier
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Park City, UT, USA
Joined Aug 2001
1,449 Posts
I did a free wheeling tail wheel on a Mosquito. I wanted to make the tail wheel retractable and it was getting too complicated to also make it steerable, due the tight space in the area of it, so I made it free wheeling. I found that it was impossible to taxi the airplane, though, due to the single rudder being very ineffective with the twin motors. What I did, then, was to set up my radio to be able to use differential power for taxiing and this works well. I shut off the differential once I am lined up for takeoff.

I use counter rotating props so that there is no yaw to worry about on takeoff. I know, it's not scale to do so but it sure makes life a lot easier with a twin.

Jim
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Old Yesterday, 09:29 AM
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Doug Bartley's Avatar
Canada, ON, Owen Sound
Joined Oct 2008
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Lay out the pattern for the part, then "cut away everything that doesn't resemble that part" hehe. While quite time consuming to do completely by hand as Pat has done, a little patience and walla, you have a unique piece you can be proud of.
If you have a Dremel or high speed air grinder/compressor, you can speed up the process by getting an appropriate cutter designed for aluminum to remove the bulk of excess materials.
I've built several tailwheel yokes now, and there's a real satisfaction from the efforts that can't be bought. Nice work there Pat!! Doug B
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Old Yesterday, 11:35 AM
The Junk Man
Jacksonville, Florida
Joined Jul 2006
1,208 Posts
Quote:
Originally Posted by Robert R View Post
vonJaerschky, I really enjoy your build logs. I learn a bunch. Thanks.

My vast experience with free castoring tail wheels on model airplanes (read as a single airplane) reveals that I am not up to the job of taxiing with a free castoring tail wheel. I safety wired it into a fixed position before the club safety officer could demand I submit to a sobriety test.

It is likely that others have had a better experience. It could be me, the plane or the smooth surfaced runway. That being said, the results were comical. The question was not how do I keep the plane straight but rather shall I ground loop to the left or to the right.

Has anyone had better success with a model with a free castoring tail wheel?

Robert
Don't beat yourself up so much.

Scale effect means stuff other than just Reynolds Numbers. If real aircraft put as much torque force on their airframes as our models do at their down-sized scale, full size single engine aircraft would have a tough time too.

Better to have either a skid or a fixed tailwheel that is just drug side-to-side than a castoring wheel... IMHO of course.

Tom
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Old Yesterday, 12:52 PM
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United States, TX
Joined Jun 2011
2,340 Posts
Actually, yes, unless ground handling is desired, you could just have a fixed tailwheel. Most of our models take off in very short distances, so you might not actually need ground-handling ability, unless you just want it.
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Old Yesterday, 01:53 PM
Isaiah 40:31
rc capo's Avatar
West Palm Beach, FL
Joined Jun 2000
679 Posts
Wow, those tail wheels look great, I never thought I could ever covet such a thing!
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Old Yesterday, 05:09 PM
a.k.a Maltone
Australia, NSW, Goulburn
Joined Jan 2005
6,671 Posts
I have to admit, I like to be able to taxi out for the take-off run - I don't like seeing a scale model carried onto the strip and pointed in the right direction - it just 'isn't scale'
I'd forgotten the twin/rudder/propwash thing - even though the model has a big rudder, it wont be in the best position wrt to the prop wash for low-speed taxiing - so it WILL be steerable. Duncan Hutson just added another couple of pull/pull wires from the rudder servo but a small, separate one maybe the go.
BTW - there can be no pushrod for the rudder - there just isn't room. The elevator will have one though but it is about 60cm long so may go for a tube-guided method to avoid flexing.

Pat
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Old Yesterday, 09:04 PM
Power Upward
GeorgeG97322's Avatar
United States, OR, Albany
Joined Jun 2007
1,236 Posts
So there ya go... Glad we all could keep you thinking. Plenty of ideas to go over.

George
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