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Rudder and tail wheel control horn

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Chris Walby19/06/2017 14:30:51
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207 forum posts
20 photos

Advice please.

I have a BH Mosquito that uses a long tail wheel rod that goes through the tail wheel bracket (plastic block), through the fuselage through a steering arm and then up through the fuselage bent 90 degrees with the rudder (epoxied in).

The issue is no matter how tight I do the screw the steering arm slips on the tail wheel rod on the bench and moving

it about.

No a problem if the tail wheel moves, but as its part of the rudder I don't fancy flying with a large dose of rudder in set on way and my thumb on the stick in the other!

Options

Take the screw out, Loctite the arm and a long grub screw in place

Try in the very limited space to move the arm an file a bit of a flat on the tail wheel rod

Engineer it so the tail wheel is not part of the rubber/steering arm assembly

Anything else?

Each option has some merit and a downside, but what have others done with success?

Thanks for your time

Denis Watkins19/06/2017 14:58:31
1752 forum posts
83 photos

dsc02120.jpgOne solution

A picture is worth a 1000 words

The mount is added upside down to hold as a bearing

And the tiller passes through  a grommet for strain relief

dsc02119.jpg

Edited By Denis Watkins on 19/06/2017 15:01:48

Chris Walby19/06/2017 15:32:42
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207 forum posts
20 photos

Dennis, thanks for the post, I' take a photo and then you'll see the problem I have!

Chris Walby19/06/2017 16:20:47
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207 forum posts
20 photos

tail wheel.jpg

Denis Watkins19/06/2017 17:10:02
1752 forum posts
83 photos

Right Chris, thanks. Mechanically your wheel lever is longer than your control horn, so the wheel has a

Mechanical advantage over the control arm.

I have, in the past, on thin bar like this, replaced the soft Philips screw with socket cap head bolt that allowed greater tightening,

and reduced the advantage at the wheel by shortening that leverage.

Alternately, the whole assembly could be built up and bent to shape from thicker piano wire

And a flat area ground on for the control arm location

Chris Walby19/06/2017 18:23:58
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207 forum posts
20 photos

Cheers, the issue is compounded by the fact that tail wheel rod is also goes up into the rudder.

Plan A unless anyone would like to chip in, Replace the screw for a Allen cap head and Loctite it on.

Other options seem to require significantly more/complexity, but if I do then move collar up & remove tail wheel, then fit castor type behind original.

Despite having both props in same direction it does not yaw on take off so a bit of rudder & castor wheel should be ok.

Martin McIntosh19/06/2017 20:12:33
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2042 forum posts
857 photos

Simply cut the rod, bend it to hook and fit a spring from the hook to the rudder, fixing the end into the rudder with a self tapping screw. Works great.

Denis Watkins19/06/2017 20:14:57
1752 forum posts
83 photos

Keep the steering Chris

A twin will castor all over the place

Ground loop for sure

Tom Sharp 220/06/2017 01:03:16
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2303 forum posts
12 photos

I have a Black Horse Chipmunk that looks to have the same set up, I have not had any trouble with the set up.

Andrew Ray20/06/2017 08:12:33
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611 forum posts
19 photos

So the rudder and tailwheel are connected with no shock absorbing properties? I think you may always have trouble with this set up. If this were my model, to have a non scale tailwheel and bracket bolted to the bottom of the fuselage would be a bit too much.

My solution would be to open up the rear end under the tailplane, cut off the extension thus removing the tailwheel and fix the connection to the rudder. I would then fit a bulkhead to mount a tailwheel assembly internally in as close to the scale position as I could get, even though the wheel would still be fixed (i.e., not retracting), for me it would look neater. I would then arrange for the steering linkage to the tailwheel to be damped in some way with either springs or fuel tube either side of the arm retained by 2 collets. I would use the existing linkage to the rudder if I could but also consider a separate servo as a possibility. This would neaten up the back end and not put so much stress on the servo. The down side is that it would mean much more work but would be a permanent fix. Sorry but the Mosquito is such a beautiful clean design and the tailwheel bracket looks out of place to me.

Depends how much work you want to put into it.

Chris Walby20/06/2017 10:44:33
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207 forum posts
20 photos

Cheers chaps there are some good ideas, I'll stick with option A for the summer and book her in for some bench time in the winter for a more elegant & permanent solution.

Chris

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