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 sequence > > Michael > > On 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. >> >> M >> >> On 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 Regards >> Laurie >> >> >> >> >> >> >> ------------------------------ >> 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, >> >> Tom >> >> >> Sent from Windows Mail >> >> *From:* Michael Stockhill <[email protected]> >> *Sent:* Tuesday, July 25, 2017 8:40 PM >> *To:* [email protected], Laurie Hoffman <[email protected]> >> >> Thanks 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, >> >> Michael >> >> On 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 Regards >> Laurie >> >> >> >> >> >> >> ------------------------------ >> 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 difference >> >> Ian McPhee >> 0428847642 <0428%20847%20642> >> 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 MT >> >> On 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. >> Laurie >> >> Sent from Yahoo7 Mail on Android >> <https://overview.mail.yahoo.com/mobile/?.src=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 regards >> Ian Williams >> >> Sent from my iPad >> >> On 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 >> <http://www.ebay.com.au/itm/Longacre-45423-40-Amp-Weatherproof-Toggle-switch-1731-/272686767789?epid=708201179&hash=item3f7d65dead:g:4QcAAOSw~FJZJvde> >> >> $ 22.95 >> Longacre 45423 40 Amp Weatherproof Toggle switch #1731 | eBay >> Longacre 45423 40 Amp Weatherproof Toggle switch #1731 in | eBay! >> >> <http://www.ebay.com.au/itm/Longacre-45423-40-Amp-Weatherproof-Toggle-switch-1731-/272686767789?epid=708201179&hash=item3f7d65dead:g:4QcAAOSw~FJZJvde> >> >> >> 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 >> <http://www.narva.com.au/products/browse/heavy-duty-2> >> >> Heavy Duty - Products - Narva >> <http://www.narva.com.au/products/browse/heavy-duty-2> >> >> >> 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 >> <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 >> <https://groups.google.com/forum/#%21topic/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 >> >> >> >> >> >> >> >> >> >> ------------------------------ ------------------------------ --------- >> You are subscribed to the Dimona Owners Group mailing list. >> To unsubscribe, send email to: dog-unsubscribe@lists. riverland.net.au >> <[email protected]> >> >> >> >> >> >> --------------------------------------------------------------------- >> You are subscribed to the Dimona Owners Group mailing list. >> To unsubscribe, send email to: [email protected] >> >>
