Conical Lycoming Rubbers

[birdofprey]

Has anyone had experiance with sagging engine mount bushings on a conical O-320? I topped my engine in June and replaced the worn out hardened rubbers with fresh ones from Spruce. During the replacement I noted that the last person to see to this had placed large area washers between the inner rubbers and the engine mounts on the lower bolts. This prevented the spinner from rubbing on the nose bowl. When I replaced the rubbers I took these out as they were not shown in the parts catalog. It wasn't but 3 months and 50 hours flying later that I noticed my spinner rubbing on the bowl and my tail pipe chafing against the engine mount diagonal. Thinking that the rubbers I used must not be of the correct composition; I ordered genuine Lycoming rubbers. I have flown those less than 10 hours and I can already see the sag developing. Anyone have a solution? I was working on a Citabria with a conical mount O-320 and noticed they use a Lord mount . Looking at the application guide the Lord mount is compatable with the O-320-A2B I have installed.

[Steve Pierce]

I have always used the Lycoming rubbers and no problems. I installed them per the drawing and torqued them to 40 inch pounds and double checked the 1.840" dimension from the engine installation drawing.

[gooeyduk]

Wrong information removed by gooeyduk

[Gilbert Pierce]

The drawing depicts a conical mount which is what an O-320A2B uses. The rubber insulators as well as the engine mounting holes are Conical or cones.
What you described, where the extended center line of the bolts converge at the center of mass is a Dynafocal Mount. In the Type 1 Dynafocal mount design the larger rubber isolators are positioned at an angle of 30°. The intent was to “focus” the mounts just ahead of the center of gravity of the engine/propeller combination. This mount reduces the engine vibrations felt in the airframe providing a smoother ride compared to the Conical mount.

Univair STC's for an O-360 engine uses a Dynafocal mount I believe. The E series and later O320's are Dynafocal.

[gooeyduk]

You are right Gilbert, I am wrong. It's the first time in my life.

[Gilbert Pierce]

I started to reply something to the effect that our President never made any mistakes but thought better of it. CHeers :)

[birdofprey]

Well I installed another set of lycoming rubbers on a 150 horse Pacer, We'll see. I followed Steve's 1.840 dimension. It didn't seem altogether different from what I was using. If you use the correct bolt's specifed in the part's book you have a very limited range of where the nut can be to pin the nut/bolt in a reasonable fashion. The 1.840 dimension seems to be at the maximum grip length allowable where you can still get a pin in.

[Eagleavn]

I have always used the Lycoming rubbers and no problems. I installed them per the drawing and torqued them to 40 inch pounds and double checked the 1.840" dimension from the engine installation drawing.



Wait what is the 1.840 dimension mean????? What are you measuring? I am in the process of installing new ones and I am not aware of that requirement.....Please school me!!!


Lloyd

[MN_flyer1]

1.840" is the compressed length of the rubber (inside washers) on the conical mount when properly torqued. You may have to make a little 1.840" notch in a sheet of aluminum to measure across the engine mount.

[Eagleavn]

1.840" is the compressed length of the rubber (inside washers) on the conical mount when properly torqued. You may have to make a little 1.840" notch in a sheet of aluminum to measure across the engine mount.



OK Thanks....

LP

[Pacer 24C]

To had to the confusion - LORD makes an mount for conical engine application- which I have on my 150hp Yankee taildragger - they can be retro fitted to most conical mount applications - they required drilling and installing a small roll pin in specific (different) locations on the mount flange and then use an eccentric metallic bushing and then conical rubber mounts with molded in washers - this mounting system does reduce vibration and last much longer than the convention conical rubbers. If you are crazy like me - having these mounts and then doing a dynamic running prop balance gives you the smoothess performance - However they are still 4 cyllinder engines with the bang bang one side -and bang bang the other side. You can never get a 4 cyl to be too smooth.

[Steve Pierce]

5123

http://www.supercub.org/photopost/data/760/medium/eng_mt_bushing.jpg

[Kurts]

Like this, for example, cut out of a piece of aluminum, with a slot deep enough so it would set right down on top of the rubber bushings and allow for an accurate measurement. Worked great. (Doh, Steve beat me to it)

Kurt

[MN_flyer1]

Man I like pictures. Thanks Steve and Kurt.

Tim

[Eagleavn]

Steve an all,

AAAHHHHH, I see now. Steve send that caliper to me.....LOL. I got them installed today and cotter pins in, I think they will make it to the next annual......I hope! The new ones are certainly better than the old ones, what could possibly go wrong if the 1.840 "smash" is incorrect?

LP

[Steve Pierce]

Picked those calipers up at Harbor Freight for $10. Great for comparing push rod tube length as well.

[chrisg]

I'm ordering new engine mounting bolts, nuts, and rubber bushings. What about the the big washers on each side of the rubber bushings? Any reason to replaces those? They are $10 each, and I'd rather spend the $80 on something else.

[Steve Pierce]

Should only take 4. Hardly any torque on them and I have never seen any cupping on them. I have a whole bunch I bead blasted and had the prop shop replays them.

[chrisg]

Yeah, only 4...oops! Still, its sounds like I can just re-use them.

Side note: I just noticed a grounding tab in the photo Steve posted above (just above the mount bolt tub). It looks like someone removed that from my mount (poorly) and didn't repaint it. I was wondering what was there.

[Steve Pierce]

The original mounts from Piper and a ground strap soldered to the engine mount that attached to an accessory housing bolt. Some aftermarket mounts have a tab welded to them for a ground strap to bolt to.

[chrisg]

One more semi-related question: the bolts that fastened my engine mount to the airframe/firewall had drilled bolts with castle nuts, but Univair specified nylock nuts. Does anyone have a preference or reason for using one over the other in this application?

[Steve Pierce]

One more semi-related question: the bolts that fastened my engine mount to the airframe/firewall had drilled bolts with castle nuts, but Univair specified nylock nuts. Does anyone have a preference or reason for using one over the other in this application?
Piper used a lot of drilled bolts and castle nuts, then drilled bolts and lo k nuts and e entually non-drilled bolts and lock nuts. I use non-drilled bolts and steel lo k nuts in this application.

[yarddart]

What are the best mounts silicone / rubber?

[Steve Pierce]

The real ones are rubber. Spruce sells silicone but don't believe they are PMA'd. I always use factory Lycoming and don't have premature sagging issues. I see Spruce sells factory Lycoming now.

[yarddart]

thanks for the info

[Chris Iriarte]

For the lessons learned file, if you're replacing old Lord mounts with Lycoming bushings, make sure you order the washers. Turns out what I thought were washers are part of the old mounts (you can probably guess what I didn't order ...) :cry:

Chris

[Steve Pierce]

I feel your pain.

[Chris Iriarte]

Inch lbs or ft lbs?

Chris


I have always used the Lycoming rubbers and no problems. I installed them per the drawing and torqued them to 40 inch pounds and double checked the 1.840" dimension from the engine installation drawing.

[Chris Iriarte]

Well, just spent half the day replacing the engine mounts with no noticeable improvement in vibration damping, which I find incredible considering the Lord mounts I took out were squashed flat and rock solid. Can't see how replacing those with almost 2" of rubber at each hard point doesn't make it better!

I noticed the 1.840" dimension coincides with the cotter pin hole in the bolt becoming completely accessible ... it's almost as if the engineers measured it!

Lessons learned (for a Tri-pacer) ... you have to drop the exhaust and release the "cap" on the carb airbox. If you try to "pry" the bottom of the loosened engine up w/o doing that the muffler hits the back of the mount and the airbox cap hits the nose strut.

With the old mounts my left wingtip was vibrating while cruising at 2400 rpm (oddly, the right wingtip is perfectly still) and I'm still getting that with the new rubbers. I'm tempted to try different prop positions but Mark's experience with aligning the prop with the crank throws makes me think I'd just be chasing my tail.

Chris

[pa20]

....snipped.....
With the old mounts my left wingtip was vibrating while cruising at 2400 rpm (oddly, the right wingtip is perfectly still) and I'm still getting that with the new rubbers. I'm tempted to try different prop positions but Mark's experience with aligning the prop with the crank throws makes me think I'd just be chasing my tail.

Chris

Chris,
While I can't give a reasonable explanation for the difference in wingtip oscillation, I wanted to throw out a few other thoughts on the resonance that you are experiencing.
When was the last time your prop had been to the prop shop? I sent 44K's prop in about a year ago, just because it had been over 20 years since O/H. Not only was it slightly out of balance, one blade was not tracking properly. After reinstalling the prop, I could noticeably hear a difference in the wind noise of the prop at idle. As soon as I laid the whip to it for T/O, I knew that every penny of the $$$ that I spent was worth it. So smooth, and seemed like I was getting a little increase of climb rate, too. Also, cleared up my sciatica, and joint pain, too:lol: Anyway, it did make a noticeable and much appreciated reduction in vibration.
With regard to the orientation of the prop, Sensenich states in their manual that if vibration is noted, remove and reinstall with a 180º change in orientation.
Keep digging, you will find it eventually!

[Chris Iriarte]

Thanks Mark. I actually had it in a local shop a couple of years ago, but wouldn't swear it was the best going-over possible. I think I might advance the indexing forward one hole ... it's currently at the (looking from the front towards the tail) 1-7 o'clock position at TDC ... I recall Brian and a Lycoming doc specifying the 11-5 o'clock, TDC from another thread.

Chris

[Gilbert Pierce]

11-5 looking from the front toward the tail, 1-7 sitting in the cockpit. When you shut down, 98% of the time that is the orientation the prop will stop at. #1 blade should be at 11 o'clock position at that point and when put your fingers on top of the blade to prop it if necessary. I think yo need to move it 90 degrees CCW when standing in front of it looking at it.

[Chris Iriarte]

Concur ... on my way to the hangar now!

Chris


11-5 looking from the front toward the tail, 1-7 sitting in the cockpit. When you shut down, 98% of the time that is the orientation the prop will stop at. #1 blade should be at 11 o'clock position at that point and when put your fingers on top of the blade to prop it if necessary. I think yo need to move it 90 degrees CCW when standing in front of it looking at it.

[pa20]

Make it look like this.....

[Jim]

Hi,

Gilbert wrote: "....I think you need to move it 90 degrees..."

I think he meant 60 or 120 degrees, can't really do a 90 on six bolts.

[Chris Iriarte]

Well, it took me two tries, but the position that finally worked was ... (drum roll, please) ... Schwaner's position ("horizontal" at TDC).

I know this hasn't worked for a few folks here, but I moved it from 1-7 o'clock to 11-5 o'clock and the vibe got worse. Pulled it off, advanced it one more position to horizontal and voilá, much smoother. Mind you, still has a 4-cylinder shake, but at least the yoke isn't throbbing anymore.

Now I just have to get used to the prop stopping completely vertical ... looks strange to me.

Chris

[andya]

which prop shop do you use?

[andya]

that's about the place mine stops 95% of the time and the blade is 9-3 at top dead center

[Chris Iriarte]

A local shop in here in NM.

Chris


which prop shop do you use?

[Homer Landreth]

Well, it took me two tries, but the position that finally worked was ... (drum roll, please) ... Schwaner's position ("horizontal" at TDC).

I know this hasn't worked for a few folks here, but I moved it from 1-7 o'clock to 11-5 o'clock and the vibe got worse. Pulled it off, advanced it one more position to horizontal and voilá, much smoother. Mind you, still has a 4-cylinder shake, but at least the yoke isn't throbbing anymore.

Now I just have to get used to the prop stopping completely vertical ... looks strange to me.

Chris

"Advanced it from 11-5 one more position to horizontal" . . . . "I just have to get used to the prop stopping completely vertical" I think you meant say Vertical in both wordings. Anyway, I think you need your prop to go to the prop shop for tracking and balancing. You seem to not be achieving success in stopping vibration. Also, stopping the prop completely vertical will impede the momentum of the first cylinder firing and taking the prop "over the top" to a position where you are using the inertia of the prop swinging down to bring the next cylinder up on it's compression stroke.

[Chris Iriarte]

No, I meant "horizontal" and "vertical". With the engine at TDC, the prop was at the 11-5 position (looking from the front). I took it off and rotated one position CCW, so that it was now (mostly) horizontal. That is, the prop is now in the 9:15-3:15 postion (since we've already established the crankshaft flange holes do not allow a completely horizontal position at TDC ;-) ... ).

Now, when I pull the mixture, the engine stops with the prop in a vertical position, which would be (off the top of my head) about 90 deg BTDC. The engine itself is stopping in the same spot ... it's just the prop that's different.

Chris


"Advanced it from 11-5 one more position to horizontal" . . . . "I just have to get used to the prop stopping completely vertical" I think you meant say Vertical in both wordings. Anyway, I think you need your prop to go to the prop shop for tracking and balancing. You seem to not be achieving success in stopping vibration. Also, stopping the prop completely vertical will impede the momentum of the first cylinder firing and taking the prop "over the top" to a position where you are using the inertia of the prop swinging down to bring the next cylinder up on it's compression stroke.

[Jim]

Hi,

When my old 290 was torn down after a prop strike we found one piston was a completly different casting than the other three. No way they could have all been the same weights. We found cracked things almost every annual, baffling, oil cooler mount, heat cuff tab, primer lines etc. My prop was earlier confirmed not to be my vibration source. If you can't position your prop to fix things, or you trust it, you might consider looking into dynamic balancing everything all at once.

[Steve Pierce]

I agree with Jim. People change cylinders with different weight pistons and over sized bores. Lots of things effect vibration besides props.

[Chris Iriarte]

As I recall, my engine had a cylinder R&R'd a few hundred hours after a field overhaul (before I was the owner). When I did the valve wobble test a few weeks ago I noticed on half the cylinders, the rocker arm shafts were full length, the other half the shafts had the plastic buttons on the end. So, there's no telling what's rattling around in that engine!

Chris

[59pacer]

Our son is building a full size WW1 Albatros fighter, but since there's no spare 180 hp Mercedes engines available, he's having to do an automotive conversion. I've suggested that he uses conical mount rubbers same as in our PA22/20. I can't find anywhere what the taper is on the O-320 crankcase to take the conical mounts. The rubber mounts themselves go fairly close to 45 degrees (i.e. 90 degree included angle), but most probably Mr Lycoming has a more accurate number.
I see that the Continental O-100 specifies a 78 degree included angle.
Anyone know what the answer is, or where I can get it?

[gliderman]

"the rocker arm shafts were full length, the other half the shafts had the plastic buttons on the end."

that is an old style rocker arm shaft and a new style.. any required replacement of the rocker shaft( cylinder overhaul) would result in this condition

Shane-o

[59pacer]

I replaced the conical engine mount rubbers on my O-320 today.
The lower left one had 'collapsed' to the point where the bolt was just starting to rub crankcase housing. On the others, the holes in the rubbers were a little 'oval', but nothing like the lower left one.
Any ideas why the large difference in condition?
I did some experimenting with the 1.84" dimension, and 40inch/lbs of torque.
A torque of 40"/lbs gave a dimension less than 1.84".
If the engine was supported by the block and tackle, the dimension came out at about 1.80".
If the engine was unsupported, the dimension came out at about 1.82".
I used the last option and torqued to 40"/lbs against the weight of the engine and left it at that.
Am I doing anything incorrectly here?

[Steve Pierce]

I made a measuring tool that will reach around the baffles and tighten to the 1.84" dimension. Had no issues that I know of and have been doing that for many years. I doubt that it makes a huge difference but that has worked for me.

[wyandot jim]

Hey Guys,
Grandson and I plan on changing out rubber bushings in the O-290D-2B in the Champion this weekend.
It appears the 290 has a different bushing than the O-320s. Is the torque and dimension the same for the O-290?
Thanks,
Jim

[59pacer]

Yes, Steve, I'd made up a couple of 'tools' and callipers to set up the 1.84" dimension. I'll just fly it for an hour or two then recheck it.
I did a bit of a search about the unusually worn left lower rubber. It seems that that event is not particularly unusual. I'm curious as to why. Looking at the engine mount itself, the two upper arms are quite light and unsupported, so the lower rubbers may get more of the load, and with torque, the left one would get even more. Who knows?


I made a measuring tool that will reach around the baffles and tighten to the 1.84" dimension. Had no issues that I know of and have been doing that for many years. I doubt that it makes a huge difference but that has worked for me.

[Larry2011]

Replacing my lower left (left seat side) rubber mount as well. (looks like a flat tire). All others look okay. Will most likely replace both lower ones if my AP/IA tells me to.

Looks like you have to take off the return oil lines and, engine block oil line “fittings”, to clear/remove, mounting bolt? (under the cylinder jugs)

Larry

[Steve Pierce]

Sounds like someone has modified your oil lines and run them between the cylinders and intake tubes. Can you post a picture? I usually replace all the bushings at the same time.

[pa20]

Replacing my lower left (left seat side) rubber mount as well. (looks like a flat tire). All others look okay. Will most likely replace both lower ones if my AP/IA tells me to.
....snipped....

Larry
Larry,
Why would you not replace all of them? They are not independent units, and if one is worn...Then they all are stressed (IMHO). They are cheap, and you are going to have to loosen all the mount bolts anyway. So, do yourself a favor and plan to do them all.
Question...You are aware that there is no specific torque on the bolts, correct? In lieu of a torque, the mounts are compressed to 1.84" (see post #2)
Good luck!

[Larry2011]

. . . sounds easy enough, will replace them all!

I believe they are draining excess oil from the valve cover, back into block/case? I am probably using the wrong wording for the "oil return lines". Here's what's in the way of removing bottom mount bolt.

13612

[Steve Pierce]

Rocker cover drain back lines. I just changed a set of bushings and didn't have to remove any. The bottom left took a little work of sliding the bushing up the bolt as I pulled it out and the same back in. Helped that I put some DC4 on the inside of the bushings.

[Larry2011]

Will take a pic of mine, when I get back at it later this week. Just found this pic to show you those engine block fittings.
Borrowed a cherry picker and, prepped everything last Saturday, before I get started.
Man, eye-balling it, looks like that oil drain back fitting will be in the way; that's a long engine mount bolt. (Bolt head facing and backing out towards front of engine)
Will try your process first Steve, before I remove more than I have to.(and DC4)

Thanks!

[59pacer]

When you are torquing up the the rubbers to 40 inch pounds, is that with the weight of the engine supported by the crane, or without any support? I would think that there would be a difference between the 2 cases, particularly with such a small torque.
Do you lubricate the bolts and rubbers?

[Steve Pierce]

I use the 1.84" measurement. I made a tool out of a piece of aluminum to make the measurement over the baffle. I check with all the weight of the engine on the mount. I also put DC4 on the id of the bushings.

[59pacer]

I use the 1.84" measurement. I made a tool out of a piece of aluminum to make the measurement over the baffle. I check with all the weight of the engine on the mount. I also put DC4 on the id of the bushings.

Thanks, Steve. I made up that tool some time ago and it works well. I couldn't see Mr Piper supporting the engine while the torque was set, but I had to ask. I was having a 'crisis' deciding whether I should use DC4 or some 'petroleum product' as a lubricant.

[Jim Hann]

Steve,

is this the correct bolts for a 57 O-320 powered 22/20? The CD doesn’t have the engine mount info and I need to replace my bushings and want to do all the hardware.

Jim

5123

http://www.supercub.org/photopost/data/760/medium/eng_mt_bushing.jpg

[Steve Pierce]

Yes, I keep a set on hand and just used them 2 days ago. They are called out on the engine installation drawing.

[Jim Hann]

Yes, I keep a set on hand and just used them 2 days ago. They are called out on the engine installation drawing.
Ugh, I FINALLY found the drawing, 14474, “Power Plant” correct old style English is killing me!

Thank you, again.

[Jim Hann]

I use the 1.84" measurement. I made a tool out of a piece of aluminum to make the measurement over the baffle. I check with all the weight of the engine on the mount. I also put DC4 on the id of the bushings.

https://uploads.tapatalk-cdn.com/20210421/0dabb196449cae2d72302d04217f609d.jpg
Grabbing the DC-4 and wish us luck tomorrow!


Sent from my iPhone using Tapatalk

[Jim Hann]

http://www.supercub.org/photopost/data/760/medium/eng_mt_bushing.jpg
Steve, going slightly off topic. I have an Experimental with an HO-360-B1B, it is a conical mount. Are the mounting details (washers, bushings, etc) the same? I haven't been able to find a definitive answer on the web but there are allusions to the fact that all -235, -290, -320, and -360 conical setups are the same.

Thanks!

[Steve Pierce]

The engine parts manual should show the bushings. As far as I know the washers and bushings are the same.

[Jim Hann]

The engine parts manual should show the bushings. As far as I know the washers and bushings are the same.
That's what I thought, and I didn't find it. After seeing your post I pulled up the my -320 parts manual and found it easily, went back to the -360 manual and they just aren't listed there or any place that I can find. Thanks for the reply!

Jim

[59pacer]

I installed new Lycoming #71032 mounts at engine overhaul. After 100 hours in 15 months, the engine is sagging badly. My record with the Aircraft Spruce (non-approved) home builders type has been no better.
I see that Superior have an SL 71032.
Has anyone had any experience of these?
They have all been set up to the 40"/lbs or 1.84" spec.
It's got so 'normal', that as the minimum idle on the engine reaches 800 rpm, I know to check for engine sag!

[Steve Pierce]

I have always used the Lycoming rubbers and get many years out of them.