Hi, I ordered the new tyre :) The Shimmy developed step by step. It was rare and now it is very often. I googled for rubber buffers. I found this. There is a specification table as well. If someone of you knows, please, give me advice if the 55 Shore grade is OK. Which length, stiffness and load would be OK? So which one should I order?
https://www.kipp.com/gb/en/Products/Operating-parts-standard-elements/Buffer-elements/K0569-Rubber-metal-buffers-Type-C.html With many thanks and best regards Győző > 2020. szept. 26. dátummal, 15:11 időpontban Mister Sutton > <[email protected]> írta: > > > > > > > > Hi Gyozo > > to try and brush up on stuff i learnt 30 years ago i asked dr google. he/she > was very forthcoming with a lot of information. some good and some could have > been found scribbled on a public toilet wall in black felt tip pen. > > what i had overlooked was that this is a resonant vibration and when its in > action (vibrating or shimmying) it is part of a tuned system(ie harmonics > through the fuselage, wings, tyres, cables, tail plane, main gear etc etc.) > so in operation when landing, if the tyre hits something as big as a pebble > or even a grain of rice really, it can initiate a small movement in the wheel > which can excite a movement or wave in the fuse (or elsewhere)and transfer to > the wings and then back again to the wheel moving it in the other direction > which again creates a wave or movement and so on and there you have a self > perpetuating resonant shimmy. and then after a while as tom said your tyre > may have worn or changed shape and may continue to be the initiator of the > shimmy(sorry if i didnt explain that very well. at least the picture was > clear in my head.) Any part of the system can add to or negate this effect by > bringing it into or out of "tune" with the rest of the system. things such as > loose cables, tight cables, worn bearings, new bearings, odd shaped tyres, > under inflated tires overinflated tyres... you get the picture. > > now after all that if youre still on board my question is, did this get > gradually worse or did it just appear one day? > > it it just appeared overnight i would look for things that would change > suddenly like things cracking or breaking (or bulging in the case of the > tyre) but if it just got worse over a period of time them i would look to > things such as gradually softening tail wheel rubber mounts, springs > stretching etc etc. > > my moneys still on the rubbers though :-) > > cheers > > ric > > On 26/09/2020 4:18 am, Tom Preisser wrote: >> Hi Gyozo, >> Be advised that after you have replaced your shock mounts, you should also >> replace your tire. A tire that has suffered prolonged shimmy will acquire >> wear that will sustain the flutter - the only fix is to grind the tread or >> install a new one. >> Tom >> >> >> On Fri, Sep 25, 2020, 13:40 Győző Horváth <[email protected]> wrote: >>> Hi Richard, >>> >>> thank you for the photo. >>> I put on some angles and a distance which can help the quantification of >>> the problem. Illustrated picture is attached. >>> As I see the kingpin angle of your Dimona and mine is very similar 96 >>> degree. However the the kingpin-fork angle in yours is only 15 degree and >>> in mine it is 36. The rake angle and trail distances are different as a >>> consequence. It can be due to your solid rubber shocks. Mine rubbers are >>> worn and soft. It is visible on the pictures that yours keep wider >>> distance. This relates to Ian’s comment with the washers. >>> What do you think? >>> I do not know what is the relation between the shimmy and rake angle or >>> trail distance. Should those be smaller for avoiding the shimmy? >>> On the basis of John’s comment and experience it can be so. >>> Does anyone know the theory behind? >>> It would be interesting and useful to collect the numbers of these angles >>> and distance from several Dimonas. Unfortunately the manufacturer’s data >>> are not published or I am not aware of it. >>> >>> BR >>> Gyozo >>> >>> >>> >>>> 2020. szept. 25. dátummal, 15:58 időpontban Mister Sutton >>>> <[email protected]> írta: >>>> >>>> >>>> Hi Gyozo >>>> >>>> i went a hunting. i was looking for some photos i had taken of mine a >>>> short time ago but instead found this one (attached) notice how the wheel >>>> axle(bolt) is only marginally trailing behind the "kingpin" (castoring >>>> axis) in the attached image where as the in the image of your aircraft lit >>>> looks to be almost an inch. >>>> >>>> let us know what you find >>>> >>>> cheers richard >>>> >>>> On 25/09/2020 3:50 am, Győző Horváth wrote: >>>>> > Hi, >>>>> > >>>>> > Hereby I attach some photos of rear gear. >>>>> > Perhaps somebody can see some disorders on it. >>>>> > The rubber shocks are worn, however evenly. >>>>> > Any further comments are welcomed >>>>> > >>>>> > Gyozo >>>>> >>>>> <IMG_1789.jpg> >>>>> >>>>> >>>>> >>>>> <IMG_1791.jpg> >>>>> >>>>> >>>>> >>>>> <IMG_1794.jpg> >>>>> >>>>> --------------------------------------------------------------------- >>>>> 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] >>>> <420.jpg> >>>> >>>> --------------------------------------------------------------------- >>>> 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] >> >> >> --------------------------------------------------------------------- >> 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]
