Hi All, OK…. The tailwheel shimmy is fixed. Here are the details for your information.
We jacked up the rear fuse so didn’t need to bend down so far. Took off the tailplane and rudder. Found there was some “play” with the connection from the rudder cables down to the tailwheel itself. Which I think was a combination of the ruder cable bracket (at the top of the tailwheel shaft) and the bearings down to the tailwheel (which was VERY loose) So the castellated nut (holding the shaft in place) removed and tailwheel assy removed totally. A close inspection of the tailwheel fork assy (it was a sprung type) was interesting. The 2 rubber blocks were bot hcompressed and quite solid But the more interesting thing was the pivot bearing system (a tube with an inner tube being the bearing) was SEIZED SOLID It obviously had been in that state for a number of years. We tried all kinds of devious methods to unseize that pivot but totally not successful … heating it, etc but it was like it was welded. SO … we cut the 2 joints of the pivot “bearing”, made up a solid inner shaft. Basically using the original Rusted in bearing tube as the new bearing surface Turned up a spacer to”fill in” the hacksaw gap made in order to separate the 2 sprung tailwheel apart Fitted the solid inner shaft using a lot of grease Drilled a hole in one end of the new inner solid shaft and used an original thru bolt to secure it. Replaced both rubber compression blocks (happened to have a couple of better ones in stock) Cleaned the tailwheel shaft roller bearings as best as possible and regreased both (there are 2) Checked the lower ball bearing and regreased it a well. Put all together again and made sure the castellated nut at the top of the tailwheel shaft was as tight as possible so it would provide some resistance (but not too much) Lock the nut, make sure the 2 * bolts holding the cable bracket also was as tight as possible. Replaced the rudder and tailplane Re lockwiring the 2 rubber shock external mounting bolts and the rudder cables ( includes the bottom rudder bearing) Test flight …. All working as it should woohoo. Best regards Ian Williams ZK-GCB and ZK-GCD New Zealand From: Ian Williams <[email protected]> Sent: Wednesday, 2 July 2025 9:00 am To: [email protected] Subject: Re: [DOG mailing list] Master brake cylinder Yep I’m thinking about that. Also the cable steering bracket on top of the tailwheel shaft maybe loose. Sent from my iPad On 1 Jul 2025, at 21:46, Kristin Nowell <[email protected] <mailto:[email protected]> > wrote: The tailwheel shimmy might also be a loosening in the bearing set that holds the tailwheel fork - quite a lot of pieces to the assembly ! On Tue, Jul 1, 2025 at 4:42 PM Kristin Nowell <[email protected] <mailto:[email protected]> > wrote: If your brakes still work it might be the reservoir or associated tubing leaking (?) The tubes stiffen over time, and the reservoir becomes brittle. On Tue, Jul 1, 2025 at 10:12 AM Ric Sutton <[email protected] <mailto:[email protected]> > wrote: Hi Gyozo. Depending on where its leaking from it may be easily repairable. Mine (dimona mk1) was leaking from the park brake valve portion of the master cylinder. if memory serves me correctly I replaced the o-rings on that valve and it was good to go. cheers ric _____ From: [email protected] <mailto:[email protected]> <[email protected] <mailto:[email protected]> > on behalf of Laurie Hoffman via dog <[email protected] <mailto:[email protected]> > Sent: Tuesday, July 1, 2025 2:13 AM To: [email protected] <mailto:[email protected]> <[email protected] <mailto:[email protected]> > Subject: Re: [DOG mailing list] Master brake cylinder We found that tightening the steering cables rectified bad shimmy on the straight shaft tail wheel. Although the suspension tailwheel with the rubber blocks still shimmied badly after that I suspect it might be related to softening (or hardening?) of the blocks over time that may be involved. With the super Cub we found keeping it highly inflated helped a lot on sealed surfaces which would have been due to less tread surface making contact with the bitumen I think. The other possibility is a slightly bent vertical shaft due heavy landings and thus throwing the geo.etry out. There is a hell of a lot of load on the tailwheel on landing particularly on rough ground. Laurie Yahoo Mail: Search, Organize, Conquer <https://mail.onelink.me/107872968?pid=nativeplacement&c=US_Acquisition_YMktg_315_SearchOrgConquer_EmailSignature&af_sub1=Acquisition&af_sub2=US_YMktg&af_sub3=&af_sub4=100002039&af_sub5=C01_Email_Static_&af_ios_store_cpp=0c38e4b0-a27e-40f9-a211-f4e2de32ab91&af_android_url=https://play.google.com/store/apps/details?id=com.yahoo.mobile.client.android.mail&listing=search_organize_conquer> On Tue, Jul 1, 2025 at 8:15 AM, Ian Mc Phee <[email protected] <mailto:[email protected]> > wrote: Over inflation can start it - we have rubber shock version. Ian McPhee +61 428847642 On Mon, 30 June 2025, 20:03 Ian Williams, <[email protected] <mailto:[email protected]> > wrote: Hi all, I have just had an interesting flight in a Dimona at Swansea in the UK. … operating on a sealed strip Had real bad tailwheel shimmying on landing The tailwheel asst is one of those rubber sprung types Any ideas the best approach to fix the prob Ian W In uk but normally New Zealand Sent from my iPad On 21 Jul 2022, at 13:02, pattoninfl.aol.com <http://pattoninfl.aol.com> via dog <[email protected] <mailto:[email protected]> > wrote: Gyozo, It's a master cylinder used in Piper Cherokees. I replaced mine about 1 year ago. I bought mine from a aircraft junkyard here in the US. Regards, Bruce Patton -----Original Message----- From: Győző Horváth <[email protected] <mailto:[email protected]> > To: [email protected] <mailto:[email protected]> Sent: Thu, Jul 21, 2022 2:55 am Subject: [DOG mailing list] Master brake cylinder Hi, It seems that there is a leakage at master brake cylinder of my Dimona. The belly is full with brake fluid, however the brake still works well. Do you have experience with it? Is it a Cessna cylinder? What kind of parts should be ordered for repair and do you know the specifications and source? With many thanks and best regards Gyozo --------------------------------------------------------------------- You are subscribed to the Dimona Owners Group mailing list. This list is archived in public. http://waikeriegliding.com/dog/ To unsubscribe, send email to: [email protected] <mailto:[email protected]>
