Rob
Thanks for that. I would never have thought of balancing tailwheel. I
use square Mc ready tyres 6pr 250x4 as am sick of the bunnings ones
from China.
I can say with PIK20E prop it really helps as with falke fixed pitch
prop but even better do a dynamic balance on the prop.
Ian Mc Phee
0428847642
Box 657 Byron Bay NSW 2481
AUSTRALIA
On 5 Oct 2015 4:10 pm, "Rob Thompson" <[email protected]
<mailto:[email protected]>> wrote:
Don't forget that if your tail wheel is out of balance it will be
much more prone to shimmy.
A static balance can be acheived quite easily.
A tiny bit of lead sheet flashing cut out to size and glued,
screwed or doubled sided taped in place will solve the problem.
Just support the well oiled shaft and see which side of the wheel
rotates to the bottom.
cheers
Rob
Rob Thompson
0429 493828 <tel:0429%20493828>
*/Please note that my new email address is [email protected]
<mailto:[email protected]>/*
------------------------------------------------------------------------
From: [email protected] <mailto:[email protected]>
To: [email protected] <mailto:[email protected]>
Date: Mon, 5 Oct 2015 11:21:28 +1100
Subject: [DOG mailing list] Shimmy and tyres
I have suspected for a while now that the square profile tail
wheel tyres are less prone to shimmy than the round ones.
Yesterday we changed to a round profile and for the first time in
ages got a bit of shimmy on bitumen on the take off roll. Landed
on grass but I will test the theory more sometime soon.
Rob
Rob Thompson
0429 493828 <tel:0429%20493828>
------------------------------------------------------------------------
Date: Mon, 5 Oct 2015 11:09:19 +1100
From: [email protected]
<mailto:[email protected]>
To: [email protected] <mailto:[email protected]>
Subject: Re: [DOG mailing list] H36 Tail wheels
I found out my previous message didn't get through because of file
size. Here it is again.
Michael is on the right track. The vertical shaft on any castor
wheel has to be exactly vertical.
What happens with the Dimona h36 is that shaft gets bent slightly
due to potholes etc. and from then on you have shimmy. The bend
can be barely visible.
The more the bend the more the excitement. I have had both the
straight tailwheel and the damped one and the only difference is
in height.
I have seen a " repaired " one that was made stronger and that
stuffed the C of G. The one with the damper bracket weighs 725 grams.
A new part definitely fixes the problem.
Regards,
John.
On 3 October 2015 at 00:08, Michael Stockhill <[email protected]
<mailto:[email protected]>> wrote:
I don't have the W&B info on my friend's H-36 here, but I do
remember weighing it and finding the numbers way aft,
somewhere on either side of the aft limits when flown solo.
My own H-36 is fine. I can't account for the difference,
suspecting perhaps an undocumented heavy repair, and the very
lavish heavy beautiful refinish that was done. It has been a
few years, but I did some calculations for adding a weight in
the nose, but with the relatively short arm it was impractical.
Life is great,
MLS
On Thu, Oct 1, 2015 at 8:19 PM, Nigel Baker
<[email protected]
<mailto:[email protected]>> wrote:
I am surprised by your comment on them being tail heavy.
I have weighed 4 different H36 aircraft and they all came
in close to each other in C of G.
See attached for my own aircraft.
Cheers.
Nige.
*From:* Michael Stockhill <mailto:[email protected]>
*Sent:* Friday, October 02, 2015 11:04 AM
*To:* [email protected]
<mailto:[email protected]>
*Subject:* Re: [DOG mailing list] H36 Tail wheels
My friend tried a later-model tailwheel fork with the
rubber dampers on his H-36. I wasn't present, but recall
that it is far heavier and put an already tail heavy bird
way out of CG limits. There were other issues that
prevented retrofit, if I remember correctly.
MLS
On Thu, Oct 1, 2015 at 4:56 PM, Rob Thompson
<[email protected] <mailto:[email protected]>> wrote:
The early H36 models had a straight un-damped tail
wheel fork which, due the wheels being forward of the
centre of gravity and the heavy tail weight can induce
some quite nasty oscillations.
As a result of this Hoffman later introduced a new
tail wheel which has shock absorbing rubbers. This
reduces dramatically the oscillations but is more
prone to shimmy.
If the tail wheel cables are too tight the steering
becomes VERY responsive to the slightest pedal
movement. If the cables are too loose you get shimmy.
Takes a bit of experience to know when it is just
right. Real pain when you have to take the tank out
each time to get it right!
Rob Thompson
0429 493828
*/Please note that my new email address is
[email protected] <mailto:[email protected]>/*
------------------------------------------------------------------------
From: [email protected]
<mailto:[email protected]>
To: [email protected]
<mailto:[email protected]>
Date: Thu, 1 Oct 2015 21:09:03 +0200
Subject: Re: [DOG mailing list] Morning Glory Cloud
Documentary
Most interesting and helpful thanks Michael. My Dimona
is also a bit of a beast on the ground compared to
other taildragger aircraft I have flown. I will keep
you pisted. Thanks for taking the time to write the
detail.
Regards.
Thys
Sent from my Samsung Galaxy smartphone.
-------- Original message --------
From: Michael Stockhill <[email protected]
<mailto:[email protected]>>
Date: 01/10/2015 20:57 (GMT+02:00)
To: [email protected]
<mailto:[email protected]>
Subject: Re: [DOG mailing list] Morning Glory Cloud
Documentary
Hi, Mathys,
I own an H-36 and also maintain one belonging to a
friend. Between the two of us, we have had some
interesting tailwheel issues. My bird was the
scariest tailwheel aircraft I had flown ( about 800
hours in various Super Cubs, Cessna 180's and 185's
and DH Beavers, etc.). If you breathed on the rudder
pedals during takeoff or landing when the tailwheel
was on the ground, it would threaten to leave the
runway, and on two or three occasions I suffered PIO
(pilot-induced oscillations) that shook my teeth.
What I finally discovered was a logbook reference to a
tailwheel fork repair. The fork was rewelded at that
time with absolutely no trailing rake. We rebuilt it
with 7 degrees aft rake and that demon was tamed. It
now actually reminds me of a normally operating aircraft.
In the case of my friend's Dimona, most landings
resulted in scary tailwheel shimmy--I thought it would
take off the tailboom. He mitigated this at first by
making wheel landings and holding the tail off as long
as he could. On the couple times I experienced it, I
braked as much and as soon as possible to get slowed
down. We tried various tailwheel tire pressures and
checked balance, etc.. It has been a while, so my
recollection is a bit vague, but what I did discover
by looking at the tailwheel fork while installed, the
shoulder of the weldment where the vertical shaft
enters the lower flanged spacer was not parallel with
the face of that spacer. Upon disassembly we were able
to discern some bending of the shaft at that point
(the shoulder of the weldment and the tailwheel
vertical shaft). We had a whiz of a machinist
fabricate a new shaft and other parts of the tailwheel
fork. I test flew it afterwards and it was a
different airplane. Rudder cables were also replaced
at a later date.
Hope some of that is of help to you.
Michael Stockhill
Polson, Montana, USA
On Wed, Sep 30, 2015 at 3:40 AM, Mathys Kuhn
<[email protected]
<mailto:[email protected]>> wrote:
Hi Everybody
I operate a mid 80’s model Hoffma Dimona in South
Africa. Lately I started experiencing a
significant tailwheel shimmy at low speed after
landing on a tar runway. Has anybody ever
experienced something similar? ANY ADVICE?
Many Thanks
*Mathys Kuhn***
*Training Captain***
T: 0825685614
C: 0825685614
F: 016 9330248
e: [email protected]
<mailto:[email protected]>
*From:*[email protected]
<mailto:[email protected]>
[mailto:[email protected]
<mailto:[email protected]>] *On Behalf Of
*Ian Williams
*Sent:* 23 September 2015 10:56 AM
*To:* [email protected]
<mailto:[email protected]>
*Subject:* Re: [DOG mailing list] Morning Glory
Cloud Documentary
Apparently only able to be viewed in Australia.
Sent from my iPhone
On 23/09/2015, at 13:05, Rob Thompson
<[email protected] <mailto:[email protected]>>
wrote:
G'day All,
For those of you who missed it, the Morning
Glory Cloud Documentary is on SBS "Catch Up"
http://www.sbs.com.au/ondemand/video/521484355510/secrets-of-a-strange-cloud
cheers
Rob
Rob Thompson
0429 493828
P Please consider the environment before printing
this e-mail.
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