Just to add to Rob's earlier post about our shimmy experience....We operate on
both grass and bitumen here at Camden. The sealed runway is very long and with
a nice smooth surface.We hadn't experienced any tailwheel shimmy for
years.After changing the tail wheel and fitting one with a brand new tyre we
immediately suffered shimmy on the bitumen and possibly on the grass without
being able to sense it there although maybe not with the reduced friction. (I
blame the forum for raising this issue and thus creating our shimmy!)On
subsequent takeoffs we consistently experienced shimmy on the sealed runway.Rob
balanced the tailwheel and this totally eliminated shimmy so balancing is
certainly worth looking into as it was the only variable in our case.While on
the topic of tailwheels, we have an H36 tailwheel spat that I can't see us ever
using. Let me know f anyone is interested in offering us a reasonable price for
it. Laurie Hoffman
From: Ian WIlliams <[email protected]>
To: "[email protected]" <[email protected]>
Sent: Monday, 26 October 2015, 6:50
Subject: Re: [DOG mailing list] More on shimmy and tyres
Hi Mathys,Thanks for your post. I am interested in your tail dolly. We have
to push our Dimona into its hangar sideways which has its own set of problems.
I have built a trolley for the main wheels but still use a temporary one for
the tail wheel so am interested in what you have in mind for the rear end.
With fuel on board and the distance of the mains from the c of g the weight as
you know is real heavy. Also needs to be a 1 man jobThe one for the mains uses
a couple of over centre frames and 4 big wheels. It works real well. I'm still
figuring out the tail one. Have a steel frame with 4 smaller wheels and hope
to make a clamp for the axel bolt and a tricky over centre lifting arm. The
tow out frame is real simple.... Two PVC circular blocks with holes on the
centre clamp Over the tail wheel axel bolt and a steel frame bolted to them to
a trailer hitch.If you are interested In our system, I can send you some
pictures as I am interested in your tail wheel dolly.Best regards
Ian WilliamsZK-GCB
Sent from my iPad
On 25/10/2015, at 8:46 pm, Mathys Kuhn <[email protected]> wrote:
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EverybodySome final feedback on the tail wheel shimmy I have experienced:I have
changed the tail wheel to a softer type wheel and the shimmy stopped
immediately. Although the previous tail wheel was only on the aircraft for less
than 10 hours of flying time, the aircraft stood in the hangar for almost a
year without flying. This might also have been a cause for the shimmy. I am now
in the process of manufacturing a dolly wheel for the Dimona to take the load
off the tail wheel for extended periods on the ground. Thanks to everybody for
the valuable information and help with this problem. I certainly appreciate
itKind Regards
| Mathys Kuhn |
| Training CaptainT: 0825685614
C: 0825685614
F: 016 9330248
e: [email protected] |
From: [email protected] [mailto:[email protected]] On Behalf
Of Michael Stockhill
Sent: 06 October 2015 03:19 AM
To: [email protected]
Subject: Re: [DOG mailing list] More on shimmy and tyres We used to have much
luck in the past balancing wood props by adding another coat of paint or more
to the light end of the prop. MLS On Mon, Oct 5, 2015 at 4:33 PM, wallace
barnes <[email protected]> wrote:
Hi All
Just putting in my little bit. To balance tail wheel and dynamic
balance of prop go to a Tyre place and get a card of stick on weights as used
on mag wheels there are a range of weights on each card. We have added 10 gms
to our new prop and the results are amazing.
cheers Wally
On 5/10/2015 3:13 PM, Ian Mc Phee wrote:
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]> 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
Please note that my new email address is [email protected]
From: [email protected]
To: [email protected]
Date: Mon, 5 Oct 2015 11:21:28 +1100
Subject: [DOG mailing list] Shimmy and tyresI 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
Date: Mon, 5 Oct 2015 11:09:19 +1100
From: [email protected]
To: [email protected]
Subject: Re: [DOG mailing list] H36 Tail wheelsI 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]> 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]> 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 Sent:
Friday, October 02, 2015 11:04 AMTo: [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]> 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]
From: [email protected]
To: [email protected]
Date: Thu, 1 Oct 2015 21:09:03 +0200
Subject: Re: [DOG mailing list] Morning Glory Cloud DocumentaryMost 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]>
Date: 01/10/2015 20:57 (GMT+02:00)
To: [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 StockhillPolson, Montana, USA On Wed, Sep 30, 2015 at 3:40 AM,
Mathys Kuhn <[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] |
From: [email protected] [mailto:[email protected]] On Behalf
Of Ian Williams
Sent: 23 September 2015 10:56 AM
To: [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]> 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
cheersRob
Rob Thompson
0429 493828
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