engine mounts

[jr.hammack]

getting ready to hang power on my exp.-18,question is,there is 1 1/2 lbs differance between a 135 h.p. mount and 150 h/p. mount. i have both and talking with lee when he owned airframes, he told me when they connducted certification tests the only structure that didn't fail was the engine mount!!
so was wondring if any one has run the 135 h.p. mount on higher h.p. engines??? the differance is wall thickness,would like to lose the weight,but don't want to lose the engine!!!!

jr.

[skywagon8a]

Use the heavier mount and find somewhere else to loose the weight. Just imagine hanging on to the back of that engine and swinging it around with the propeller spinning during all of the maneuvers which the airplane will be performing!

[Fortysix12]

I think the Super Cruiser 108 Hp 150hp upgrade uses the same mount only with some slight reinforcement .

[cub_driver]

If there's 1 1/2 pound difference I would tend to believe there is a pretty good reason piper engineers added the weight.

[Steve Pierce]

I have the drawing for the engine mount for the PA16 (108hp), PA20 (125-135hp), PA22 (108-160hp) and the Pawnee 150hp and they are the same base mount. Only difference were brackets and such for stuff that was bolted to the mount. The PA12 and 14 mount gets the lower legs either replaced with a thicker tube or a tube split and welded over the original. The base number for the PA18 mount is 12351 with different dash numbers for the 125hp, 105 & 135hp and the 150hp. I will find out the difference. I don't remember having to change the engine mount on any of the STCs to got from a 105hp Lycoming up to a 150/160hp.

[jr.hammack]

steve,
the 135h.p. vs. 150h.p. have the same renforcements and visually the same,only differance is wall thickness!!

was hoping to find a light weight junky that had already tried it,couldn't find any thing on failure of a piper engine mount,but then i'am not a computer expert!!
mounted a hawker to the interior firewall,so i'am trying to be as light forward as i can,one solution creates another problem to be solved!!

jr.

[Steve Pierce]

Ron's started life as a 135hp and I don't remember him changing his engine mount with the O-320.

[Ruidoso Ron]

Shhhhhhhh!

[jr.hammack]

durn ron,
had i known that flying with you friday i wouldn't had ta ask a stupid question over the internet !!! guess it's already be proof tested with by you!!

jr.

[Steve Pierce]

Well Vicki at Tamarack opened my eyes to an AD that I guess I forgot about and then Jason reminded me of it today.

72-01-07 PIPER: Amdt. 39-1369 as amended by Amendment 39-1434. Applies to Piper Model PA-18, PA-18-105, -125, -135, PA-18A, PA-18A-125, -135, and seaplane versions of those models which have been modified after May 14, 1968 in accordance with Supplemental Type Certificate SA 136 AL to incorporate the installation of the Lycoming O-320 engine (150 HP). Factory delivered models having serial numbers 18-3771 and 18-3781 and above, incorporating the O-320 engine, are not affected by this AD.

Compliance is required as indicated.

To prevent possible failure of the engine mount, within the next 25 hours' time in service after the effective date of this AD, unless already accomplished, install engine mount, P/N 12351- 12, in accordance with Piper Drawing Number 12351, Mount Assembly-engine, including Revision J dated January 16, 1968, or an equivalent approved by the Chief, Engineering and Manufacturing Branch of an FAA region (or in the case of the Western Region, the Chief, Aircraft Engineering Division).

NOTE: Engine mount assembly P/N 12351-12 may be identified by the gage of Tube "A" and Tube "B" which measure .049 inches, and by the incorporation of two reinforcing plates, number 14438, mounted at the lower right engine attachment points as shown on Piper Drawing Number 12351, Mount Assembly-Engine, including Revision J dated January 16, 1968.

Amendment 39-1369 became effective January 27, 1972.

This Amendment 39-1434 becomes effective April 17, 1972.

Looking at two mounts I have here, one new Univair mount has two finger patches welded to one of the tubes connected to the engine side like the AD states. They other does not and feels a lot heavier. I guess I have been searching ADs by PA18-150 and missed this one.

[jr.hammack]

vicki,jason,steve,
jason looked at both the heavy and the lighter one when he was up,when outside miked both measures the same both have the same finger reinforcements,the more i get into it the more confused it gets,if the lighter mount is before the ad shouldn't it measure different outside dia. and not have the reinforcement??
or did i not understand?? like it was commented maybe better ta bite the bullet and put the heavy mount on!!! the only problem is a pound here,a pound there,it starts to add up to
another heavy cub,i know go a diet,its healther and safer!!

merry xmas everyone


jr.

[Steve Pierce]

I will take a picture of the difference tomorrow. The tube will measure the same outside thickness. 5/8" .049 and .035 wall both measure .625 outside. I will post the picture tomorrow. I will bet money your light mount is missing this reinforcement.

[Steve Pierce]

Here are pictures of a new Univair 12351-015 engine mount for the 150 hp Super Cub. These are the patches that are referenced in the AD. This mount weighed 3.55 lbs. and another mount I have without the reinforcement plates weighed 3.30 lbs. Not sure which tube is A or B but 5/8" .035 wall weighs .2205 lbs. per ft. where .049 is .3014 and 3/4" is .2673 vs. .3668. I think something is amiss with your mounts.

[jr.hammack]

steve,
not arguing at all,iv'e got four mounts total,all have the reinforcement shown in your photos,even a smith exp. made by nick himself,just wondering if the light mount was modified after the a.d.??thinking smiths mount was the heavist,probably made from heavier wall totally!!
will probably use the heavy wall mount,seems that the more ya learn about cubs,the less i know!!!

appreciate everyones experiance,steve you always go the extra mile,THANKS!!!

merry xmas.

jr.

[Steve Pierce]

I think that explains it. I bet Nick made it with thicker walled tubing and that is why it is heavier. I need a mount for my SC since I am going from the C90 to the O-320B. Found one from a guy I know on the shortwingpipers.org but it has a kink and no patches per the AD si I guess that was a bust. $579 from Univair isn't in the budget at this point. Anybody have drawing 12351?

Jr. I didn't think you were arguing, just looking for answers. I know you wouldn't argue with anyone except the government.

[cubscout]

Excellent, clear pictures, Steve. That helps a lot.

Soooo, then, it appears that the A.D.applies to STC SA136AL. If someone, hypothetically, had STC SA388EA, presumably the A.D would not apply?

Thanks. cubscout

[Steve Pierce]

That would be correct. I intend to find out which tubes are A and B and there might be a jig built for a little modification.

[tamarack]

Cubscout,

re: STC SA388EA

Which one is this? How is it different from SA136AL?

Thanks,

Vickie

[cubscout]

Vickie, STC SA 388EA is the old J.A Myers STC now sold wy Wag-Aero.

Thanks. cubscout

[robert norberg]

More motor mount confusion! I have a '54 135 pa-18a. In 1970 it was converted to an 0-320A-2B by stc. SA894WE issued to Sam Flint, Colorado. I have tried looking at the FAA STC lists and basically get a "yeah, it was issued, but you have to call Denver to get text." Has anyone ever heard of this, or done this conversion?? I have a slightly "tweaked" motor mount--all 4 firewall attach points don't touch the ground, one is in air about 1/2 inch. I don't want to re-build this mount and find out it isn't right. It doesn't have the finger patches that Steve showed in his pics. Maybe I should just buy the $579 Univair mount, 12351-015 like the pics and be done. Hate to just stare at my mount and wonder!! Thanks all Bob N

[Steve Pierce]

Funny, I checked an airplane tonight for this patch and looked at my 135 hp mount and a bent 150 hp mount. All I need is time, and money I guess.