Thorp Air Command - T18.net

Seeing as this is my first engine install, I have some very basic questions. Below is a picture of my engine mount. Do you simply put the rubber isolators as shown or do I need to use large washers on both sides of all 4 isolators? From my Internet research, it appears I will only need the large washers on the bottom bolts, but do the washers go on both sides of the isolaters, or are the washers used for shimming if needed?

Ryan I had my cowl up so I went to have a look at my mounts . It's been a while since I looked regarding the washers . I only have the washer on the nut side of the mount . Are you using new mounts ? They do have a shelf life according to the manufactuer . If I remember right I had to "shave down" the steel spacer a bit to get the right thread clearance . My engine is an 0-360 . May be different for other applications ?

RB

Ryan: looked at your thread on you buying a 10-360-M1B engine and Jim Mantyla's engine mount picture appears only to have washers on the nut side as is my aircraft.

You add washers on the nut side. You may have to add a thin washer or/ remove a washer to obtain proper torque and bolt hole alignment to install the split pin. (between 1-3 washers will work)

In a lot of installations it is adviseable to put a washer also under the bolt head (to prevent ware) but due to the construction of the metal rubber mounts, the metal plate acts as a washer to apply pressure to hold the assembly together. Sorry this is the best picture I have on the mount installation on my aircraft.

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Victor J Thompson
C-GIRQ
In memory of Dad

good info guys, thanks. The rubber isolators in the pics are new, but I didnt think about the shelf life. They have been sitting for a pretty good while. I need to look into this further. I guess I should go ahead and buy some brand spanking new lord mounts.....but dang, they aint cheap!

Make sure the spacer between the isolators is there and is the proper length. I usually call the Barry mount guys for all the up to date info at mount swap time. Been using Barry mounts for years and have found great support and reasonable prices.

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Bob Highley
N711SH
SN 835
KLAL

yep, I didnt show the spacer in the pics, but its in there. Thats a good idea about calling them for the latest info.

FWIW I had "new" VIP mounts that came with my project , but by the time came to install them they were 20+ years old (based on the cure date stamped on them) . I called the folks at VIP and told them the cure date on the mounts and they said the mounts had a shelf life of 5 years from the cure date . I pretty much knew I was not going to put 20 year old mounts on a zero time engine . Not sure if the 5 year shelf life is completely valid , but fuel hoses , tires and most other rubber products have a shelf life . I bought new mounts .

RB

I'll be hanging an 0-320-E2D on Project 1 next month. What are the preferences on mounts? Lord or Barry? And is Spruce the best source or does somebody have a better place?

Thanks, T

Aiming for Kentucky Dam for Project 1

If you decide to go with Barry, I have a complete set of 4 mounts that you can have for $150+shipping. They are a couple of years old, so you may want to check with Barry about shelf life. If you buy them and are not happy with them after you get them, I will refund your money if you will mail them back to me.

I bought the Barry mounts a few months ago from another Thorp owner, but like Rich, I decided to bite the bullet and buy a new set of Lord mounts. I believe he had had them for a couple of years prior to me buying them.

PM sent

So if the engine mounts have a 5 year shelf life what does that imply for installed service life? I'd have thought that the answer would be max 5 year service life, but to my mind seems a little excessive. Do engine mounts typically get replaced on condition or at set schedule?
Just curious I'm probably at least 5 years away from hanging an engine.

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Stug

Like I said when I called the VIP factory about my 20 year old new mounts and was told they had a 5 year shelf life , that put an alarm between my ears ! Not sure about service life ? Call the manufactuer to get up to date info . Would you put "new" 20 year old mounts on your new engine ? According to VIP you should be inspecting your engine mounts at every annual to check for cracking , sag and separating . Go to their web site they have a check list . It tells you about not spraying engine cleaner on the mounts , along with other chemicals . They suggest covering the rubber during engine cleaning . Honestly , I think a 10 + year service life would be more in the ball park . Your mileage may vary . BOOM !

RB

The A&P that does my Annual Condition inspection told me that to reduce the sag to rotate the mounts 180deg every annual.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

Bruce: That sounds like info I can use ! I rotate my shoes in a similar manner !

RB

Stug: Military, supply ware houses and parts distributors: shelf life is put in place for rubber parts to allow parts in stock to be rotated in a timely method to be issued for use. Oldest parts issued 1st and new parts are stocked at the back of the bins eventually being issued before the shelf life has expired. Just like food in your grocery store. This applies to most rubber parts, or rubber impregnated parts. Specifically aircraft tires, rubber fuel tanks, rubber pressure lines, o rings (Packings) engine mounts, radio isolation mounts, elastomeric bearings (pivot bearings) etc.

Shelf life varies between different parts, shelf life is generally dictated by the manufacture. So what happends when the shelf life is exceed? The part can be inspected, tested and sometimes re-lifed prior to usege. While I have re-certified parts for the RCAF, even O-Rings (Operation necessity) parts of low value (Cost) like O-rings are usually scraped, parts like Pivot Bearings for the MR Head of a Bell 412 costing several K are sent to the contractor to be re-certified prior to use.

In-service life: once a part is installed shelf life is no longer a concern. Some parts do not have a in-service life once installed on a aircraft, ridged line clamps, O-rings, airframe trim etc, These parts are replaced on condition. Some parts like tires and hoses are given a in-service life. Tires on a fighter may be replaced after X number of landings or for transport aircraft by simply tread ware. In the RCAF, aircraft flexible hoses (neoprene and Butyl) are given a 8 year in-service life (based upon manufacturing date data on the metal tag/ or aircraft log set data). This is based upon historical data, lines are exposed to elements, rub, chafe and you want to replace them prior to them bursting.

My 33 yr military carreer I rarely saw engine mounts with in-service life values rather replacement was due to poor performance. Helicopters let you know quickly that a dynafocal mount needs to be replaced, the vibration intensity increases with speed / torque applied. Fix wing aircraft the vibration is felt throught the fuselage and can be a gradual increase. Usually inspections and functional tests catch weak engine mounts prior to the vibration cenario. Heat, oil, dirt, any petroilium product sprayed on and poking with metal objects is very un-friendly to engine mounts.

To install a exceeded shelf life engine mount doesn't make much sense to me, if you go to the trouble of removing and then installing a engine it is nice to do it once with mounts that are serviceable. Due to the nature of the Thorp's engine mounts, rotating the mounts as has been stated can extend the life. Other engine mounting designs or applications rotating is not an option usually due to shape or space issues.

Rich is correct on his Inspection details, mounts need to be inspected as a min on the annual Inspection. Replacement to me is on-condition item ~ deteroration / saging / vibration.
Hope this helps.

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Victor J Thompson
C-GIRQ
In memory of Dad