Thanks to you all for the great info. I'll be having a close look
at the tailwheel shaft this weekend.Cheers,Greg Wilson---- On Thu, 27 Jul 2017
12:18:01 +1000 John Callahan<[email protected]> wrote ----Tail
wheel shimmy on the H36 is almost always caused by a slight bend in the
vertical shaft where it comes out of the fuselage. Sometimes barely visible -
you have to take the fork assembly out to check it.John.On 27 July 2017 at
07:15, Michael Stockhill <[email protected]> wrote:Greg, what you have sounds
very similar to the problem we rectified on my friend's h36, which also has the
springless tailwheel fork.It has been a couple years and this greybeard's
memory is flawed, but here is what I recall:What I found was that the tailwheel
fork's axle (vertical, if that term is valid), was misshapen rather than round,
and at its base, where it is welded into a larger tube that is a component of
the fork, there was some wear. The wear meant that that edge was not perfectly
perpendicular to the axle axis, but was in a plane a degree or two off.Most
landings could shake you teeth out. We tried various tire pressures, etc.If it
has ever been disassembled there is a chance that all the bushings and spacers
were not reinstalled in proper sequenceMichaelOn Jul 26, 2017 2:51 PM, "Greg
Wilson" <[email protected]> wrote:I haven't found propwash to be a problem
but tailwheel shimmy is something my H36 suffers from. I've tightened the tail
wheel steering & rudder cables as much as possible but is hasn't helped
much.Mine is "A" version without tailwheel shock absorbers. I generally land on
grass & keep taxi speed down to avoid the shimmy. Not only uncomfortable but
also chews out tailwheels fast.Anyone have a solution?Thanks,Greg.Greg
Wilson---- On Wed, 26 Jul 2017 22:38:12 +1000 Michael
Stockhill<[email protected]> wrote ----Thanks, Tom and Laurie,I live in Polson,
Montana. I did fly another H36 and don't recall it having that tendency,
however it had its own problems, being very tail heavy and with a tailwheel
fork issue of its own that caused it to set up an oscillation that would shake
your teeth out. I was able to sort that out for the owner.You have given me
lots of ideas for some trouble shooting. It is refreshing to know that this
tendency may not be typical of the breed.MOn Jul 26, 2017 1:00 AM, "Laurie
Hoffman via dog" <[email protected]> wrote:Thanks Tom,I was thinking
something along these lines. An issue between rudder and tailwheel interplay
perhaps. I know of instances of steering/rudder cables being too tight that
have caused Dimona operators over controlling problems during the ground run.
The comment of the previous owner of Michael's aircraft and the faulty
tailwheel repair seems to confirm the possibility.I'm no engineer though and
Rob, Nigel, Macca and others would know best.I don't have the wide T/W
experience that you have Michael, about 1000hrs in SuperCubs, a few in Pawnees,
Callair and some several hundreds in TMGs. I've flown quite a few TMG types and
I have to say that after something like 15 years of operating, our Dimona is an
absolute delight both in the air and on the ground.The other owners and myself
have taken off and landed in what on occasions were horrendous cross wind
conditions and the Dimona has handled them all wonderfully despite not having
differential braking.If possible i would strongly recommend that you fly in
another H36 to see if there is any difference to yours. Just remind me where
you are located pls.I don't believe asymmetric blade effect to be of any real
consequence with the L2000 and doesn't appear to be noticeable with the
L2400.Compared with the other aircraft that you have flown the Dimona certainly
does need sensitive control input. Just a thought, but after your extensive
experience with US clockwise rotating engines and even though you are aware of
the difference, any chance that you may still be unconsciously applying right
rudder during rotation? Also wondering if you have any gliding experience in
FRP aircraft Michael with which you can compare the H36.Best RegardsLaurie On
Wednesday, July 26, 2017, 12:17:05 PM GMT+10, <[email protected]> wrote:
Dear all, My dimona S.n. 3506 had developed ovalized bolt holes on the
tailwheel steering horn over time (circled green in attached drawing from H36
parts manual). Although I had previously adjusted the turnbuckles to align the
rudder and tailwheel, a subsequent off center touchdown would misalign the
rudder and wheel – resulting in a startling condition in which straight rudder
input yielded a strong turning output, ground loop imminent. The cause of the
problem became apparent when I held the rudder firmly while twisting the
tailwheel – three degrees of play was then evident. Disassembly of the
tailwheel drive horn revealed the wear on the horn tube where it is fixed to
the tailwheel shaft with two M10 bolts. Repair was accomplished by slightly
reaming the oval holes until roundness was restored, and then bushing the M10
bolts for a tight fit – no play even before tightening the bolts. I now
include visual tailwheel udder alignment check as part of my positive control
check before flight..even a little misalignment results in nasty directional
behavior right after the wheels leave the ground and right after they touch
down. Cheers, TomSent from Windows MailFrom: Michael StockhillSent: Tuesday,
July 25, 2017 8:40 PMTo: [email protected], Laurie
HoffmanThanks Laurie and Ian.I've owned my Dimona 16 years. I have about a
thousand hours in taildraggers up to a DC-3, owned a Cessna 180, and flew a
dehavilland Beaver for a few seasons before moving onto other things. I have
flown many different tailwheel types and must say that my Dimona's ground
handling is the most sensitive (to the point of occasionally being seriously
uncomfortable) of anything I recall having flown. (When I asked the previous
owner about crossword handling, he said to just go someplace else.)There were
at least a couple instances where I had PIO on the rudders during landing
before I determined that the tailwheel fork had been repaired with zero degrees
castor or rake. It was very squirrelly and easy to over control on the ground
before I reworked the tailwheel fork. That made it much better, but it has
always wanted to head for the weeds (to the right) as the tail comes up for
takeoff. (Perhaps when the tailwheel leaves the surface.)Much of the time I
attributed this to habitual taildragger habit patterns of using right rudder
during takeoff to compensate for P factor and gyroscopic effects rather than
left rudder on the Dimona.Inflight handling, trim, and rigging are fine, other
than pretty heavy ailerons in powered cruise flight.Although the book suggests
a three point takeoff, I have always raised the tail at thirty knots or so (I
have never really noted that speed as it is only when the airplane is ready, so
don't hold me to that number). Wings are level with no aileron input to cause
adverse yaw, but there is a significant yaw excursion.I seem pretty much used
to this now, but have been working with a friend so he can fly my bird. He was
a Naval aviator--a Top Gun spin instructor in F-18s etc. After a few takeoffs
threatening a visit with the weeds he said he's never flown anything before
that he couldn't comfortably take off. I have offered to come up with a way of
providing him with a cat shot!This doesn't seem normal. It is like there is
quarter right rudder as the tailwheel leaves the ground, so we have lots of fun
overcorrecting.I really want to revisit neutral rudder and tailwheel to see if
there is any deflection, but last time I looked I couldn't see anything out of
the ordinary. I will get into the service manual soon (after an engine repair
on my PIK-20E, with is another eventful story) and look into rigging.So anyway,
what do you folks experience? This is way more than P factor. It is always a
challenge to stay anywhere near the runway centerline on takeoff roll. I tend
to let it find a line it likes rather than risk overcontolling. None of this
seems normal for an aircraft with a long tail arm, although the maingear seems
quite a bit forward of most designs and configurations.Cheers,MichaelOn Jul 25,
2017 4:48 PM, "Laurie Hoffman via dog" <[email protected]> wrote:I get
the impression that Michael experiences the aircraft pulling to the right on
most/all of his take offs on rotation?Cross winds would explain only some of
these. I can't recall ever noticing it Michael. Is it yawing only or is there
some initial roll there too?If you simulate the low speed flight in the air
does that reproduce it? Possibly a rigging or control deflection issue.Best
RegardsLaurie On Tuesday, July 25, 2017, 10:33:18 PM GMT+10, Ian Mc Phee
<[email protected]> wrote:Yep RHS x winds are always an issue. Have a look
at the bight of prop and upward going prop and downward going prop. Big
differenceIan McPhee 0428847642 Box 657 Byron Bay NSW 2481 On 25 Jul 2017 10:03
am, "Michael Stockhill" <[email protected]> wrote:Have any Dimona operators
found that their bird diverges to the right when rotating for takeoff? Mine
consistently does that as the tailwheel lifts off. After 400 or so flights I
think I am past adding right rudder for a prop that turns contrary to all the
taildraggers I have flown. Michael Stockhill Polson MTOn Jul 22, 2017 3:23 PM,
"Laurie Hoffman via dog" <[email protected]> wrote:Rob you forgot to
mention that on two of those occasions when we had prop work done, that there
were other faults also.The blades looked like they had been refinished by
someone who had never spray painted before. At least once there was an issue
with seal installation with grease being sprayed everywhere on use.LaurieSent
from Yahoo7 Mail on Android On Sun, 23 Jul, 2017 at 6:16 am, Ian
Williams<[email protected]> wrote: Hi Rob,Can you explain the difference in
TBO between the BT and T blades ? I thought both were the same.Best
regardsIan WilliamsSent from my iPadOn 22/07/2017, at 7:51 PM, Rob Thompson
<[email protected]> wrote: I just heard that GFA has adopted the CASA rules
on overhauling propellers. See
http://services.casa.gov.au/airworth/airwd/ADfiles/equip/prop/PROP-001.pdf
This means that as soon as it is documented in the system there is no longer a
calendar time for overhauls. Ian McPhee has been dealing with Prop Care
(www.propcare.com.au) in Brisbane for Hoffman overhauls and hopefully they will
be soon doing work on Hoffman props. We are continuing to have a nightmare
run with Eric at Australian Air Props at Bankstown. 3 times in the past 2 years
our prop has come back to us with problems. Once WAY out of balance then next
time set much too coarse and only pulling 2000 at full power. Then recently he
sent it back to us with the counterweights set incorrectly and the rpm was
fluctuating on run up and early take off roll. Add to that he charges a
fortune because he knows that the only other option in Australia is to send the
props to Germany. Up near $4000 now for about 10-15 hours work. Fingers
crossed that the Brisbane mob will be able to do them. Rob Thompson 0429 493
828 From: [email protected] <[email protected]> on
behalf of Michael Stockhill <[email protected]> Sent: Monday, 17 July 2017 4:23
AM To: [email protected]; Laurie Hoffman Subject: Re: [DOG mailing
list] H36 Ignition Switch (and brakes) For what it is worth, the mag
switches on my Aztec with similar magnetos are rated at 6 amps 125V a.c./dc.
The p lead grounds the primary coil. I found one source that says the primary
coil puts out about 150 volts. The secondary coil puts out 10-15000 Volts. 40
amp or even 20 amp rated switch looks like overkill for whatever reason. Maybe
consevative because we only get one of them. Michael On Jul 15, 2017 1:29
AM, "Laurie Hoffman via dog" <[email protected]> wrote: Hi Tom and
Mike, Rob and I have the wreck of an H36 from which we have salvaged many
parts for our functioning H36, especially the L2400 which we had top
overhauled. Tom, I gritted my teeth and dived back into the wreck to recover
the ignition switch and a panel switch. The wreck is already well dismantled
however I still had a cow of a job getting access to the switches and removing
these. I dread to think how much time it would take to install a new switch in
the original position in a complete panel. My strong recommendation is that if
you have an ignition switch failure seriously consider installing a new switch
in another location on the panel, simply reroute the wiring from the old to the
new and then cover up the old switch and placard the new. Although
psychically the switch toggles and bodies appear the same, the switches have a
very different rating. The panel switch is rated 15A while the ignition switch
is rated 40A! The link that you posted to a new switch I just noticed is only
rated 20A. Maybe something like this one Tom.... Longacre 45423 40 Amp
Weatherproof Toggle switch #1731 | eBay $ 22.95 Longacre
45423 40 Amp Weatherproof Toggle switch #1731 | eBay Longacre 45423 40 Amp
Weatherproof Toggle switch #1731 in | eBay! In Oz I have found Narva
(driving light manufacturers) switches which look suitable. Heavy duty and this
one rated at 50A for 12v. Heavy Duty - Products - Narva Heavy Duty
- Products - Narva The wreck is a Mk2 by the way while our operational
H36 is a Mk1 so if anyone needs a good Mk2 wing or two, let us know! Re
hydraulic fluid, we use only OM16 which I gather is equivalent to 5606.
Best Regards Laurie From: Michael Stockhill
<[email protected]> To: [email protected] Sent: Saturday, 15 July
2017, 10:13 Subject: Re: [DOG mailing list] H36 Ignition Switch (and brakes)
Hi Tom et al I think I found that the MS O rings are okay. Mine were fine
through two rebuilds (preventative maintenance each time I put on new tires)
over 16 years. Mike On Jul 14, 2017 10:01 AM, "Tom Preisser"
<[email protected]> wrote: Hi Laurie, I have what I believe to be an
ignition switch in my spares. Can't be positive without digging behind the
panel to look at my installed switch, but you can check your removed switch
against it. The spec is MS 35058-22 http://www.bandc.aero/
toggleswitch-MS35058-22.aspx And I think it could be a different spec to the
other fuel pump, etc switches (beefier), given that it has a separate entry
than the 15A switches in the old H36 parts manual (with part numbers no longer
valid for Diamond)... BTW on brakes (and thanks Mike for your advice)... just
now installing a new caliper piston which makes the O ring fit much better in
the cylinder (seems I had to take off too much corroded material from the
groove of the original installed one, so it no longer sealed tightly)... For
those of you running DOT3 fluid, I have obtained some EPDM O-rings to use
rather than the BNR (nitrile) MS-28775-218 O-rings supplied to me by Diamond
(which they may have sent probably because the HK36 and DA20 use 5606 aviation
brake fluid). See this RAS thread for the details on why BNR is not suitable
for DOT3... https://groups.google.com/ forum/#!topic/rec.aviation.
soaring/4MiwHrkryFg And I talked to a lady who has worked at Cleveland Brakes
for decades, and she gasped!! when I said that Hoffmann used DOT3. She says
Cleveland only recommends aviation brake fluid - but I'm sticking with DOT3 as
per the US type certificate! Cheers, Tom On Thu, Jul 13, 2017 at 7:26
PM, Laurie Hoffman via dog <[email protected]> wrote: Hi All,
After extensive investigation into intermittent electrical problems eventually
developing into a situation where the motor had to be shut down in flight due
to rough running, it appears that the culprit is the ignition switch.
Physically, the switch appears identical to the other original panel toggle
switches operating fuel pump, avionics, strobe etc. Does anyone know if
they are the same switch and also is there anyone out there in DOG land who
might have specs for the switches? Best Regards Laurie
From: Greg Wilson <[email protected]> To:
[email protected] Sent: Sunday, 18 June 2017, 8:10 Subject: [DOG
mailing list] Easy fit ADSB These are a very easy install and cheap too.
https://www.recreationalflying.com/threads/wow-these-are-good-looking-gadjets.161803/
Greg Wilson ------------------------------
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