Engine Mount Washers

T

Tom

MEMBER
Iowa
Pressing on with my Clipper rebuild and there are large area fiber washers between the engine mount and firewall on both the front and back sides of the firewall. Have checked all the parts manuals and blueprint CD but can't seem to locate. Any suggestions?

Tom
 
Tom, I have always wondered what those washers were for and what they were made of. I thought of using phenolic but it seems softer than phenolic. I also was never sure where Piper put them. I will have to look at my pictures to see if I had them on both sides of the firewall. Could they have been to seal the holes, isolate vibration, any other ideas?
 
Hi,

......Could they have been to seal the holes, isolate vibration, any other ideas?

I'd guess they work like the nylon washers we put under the screws on the exterior of our planes, anti-chafe for the firewall.
 
Steve Pierce said:
Tom, I have always wondered what those washers were for and what they were made of. I thought of using phenolic but it seems softer than phenolic. I also was never sure where Piper put them. I will have to look at my pictures to see if I had them on both sides of the firewall. Could they have been to seal the holes, isolate vibration, any other ideas?
Click to expand...

Steve, I had the very same idea and came close to offering to make him some from phenolic, but I agree, I think its too brittle. Since then I have had another off the shelf Idea... When I was a young man I ran a small engine shop for our local hardware dealer...Many of the lawnmower blade adapters used to have two fibre washers on either side of the blade to provide some grip with a little forgiveness...these washers were about 1/8" (or slightly less) thick, about 2" in diameter with a 3/8" hole...
Could it be that is what Piper used, given his propensity to use off the shelf hardware? What do you think?
 
Steve, yes I think phenolic would be a little too brittle. I would reuse the ones that I have but they are curled and somewhat hardened after sitting in a box for 43 years. If I had to say, I think they were for vibration isolation mainly. Do you know if all the short wings had the fiber washers installed? Seems odd the parts books and blueprints do not show them. Maybe I'm just not looking at the right drawings?

Tom
 
steve

since you found them, have you seen them on Super Cubs? If any one gets one, let us know what they appear to be made from (old ones sound like they are unrecognizable material?)
 
I have seen them on Super Cubs. I found another one in the J3 parts manual 81342-22 but no reference in the PA16 parts list nor the PA20 nor PA22 parts manual.

From the drawings for washers:

80122-43 1 1/2" OD 437/447 or 417/447 ID drawing isn't very clear .062 thick Fibre is the material with a note "Purch. was J2-885"

81342-22 1 1/4" OD .448 ID .062 thick Fibre for material.
 
Other than the OD I wonder how they compare to the blade washers I mentioned earlier, I'll try to round one up for comparison.
 
Steve-Yes, I think you found them! The 80122-43 washer dimensions match exactly with what I have from my Clipper project. The ID appears to be about .437. Going to order some from Univair and see what I get. What drawings do you look at for washer specs? Thanks for the help.

Tom
 
The SWPC Vagabond CD has a lot of these small parts. They need to rename it in my opinion. It has parts from the J3 on and has been very helpful to me. :idea: Let us know how it turns out.
 
Reviving an old thread to see if anyone knows whether these fibre washers were supposed to be on '55 pa-22-150's or not. I'm about to re-install my motor mount to the firewall with new hardware and didn't see any mention of washers between the firewall and mount in the Piper drawings. However when we removed the old mount there was a mixture of fibre washers and steel (steel were thin ones stacked to be equivalent to the fibre washer thickness) at the 4 locations!

For the life of me I can't find any mention of them in the Piper drawings or Univair's parts manual for the pa-22-150. :confused: Also makes me wonder if the length of the bolts mentioned in the drawings were for no washers.
 
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I just looked in several engine installation drawings and they are not depicted nor does the part number show up in the numerical index in the back of the parts manual on the PA22-150. It does on the Super Cub. I know they installed those washers on PA22s and PA16s at the factory because I have found them multiple times there.
 
I also did not find any washers required on the engine mount to firewall drawing for our 55 TriPacer. I have seen them installed on tube fuselage Piper’s to bring the engine thrust line into spec’s. Not sure if that was a factory practice or a field modification after an incident.
N2709P
 
N2709P said:
I also did not find any washers required on the engine mount to firewall drawing for our 55 TriPacer. I have seen them installed on tube fuselage Piper’s to bring the engine thrust line into spec’s. Not sure if that was a factory practice or a field modification after an incident.
N2709P
Click to expand...

I don't see how they would change the engine thrustline. All I have seen are on all 4 corners except on the Lycoming powered Super Cubs with swing out mounts where they committed the one on the lug that has the part that stops the mount from going to far that is the same thickness as the washer.
 
If the washers are mounted between the motor mount and firewall they can change the engine thrust line. Obviously if the same thickness and number of washers are used on all four courses there would be no angle change. I have found different thickness of washers and numbers of washers installed. If you put a washer on each right side leg of the mount, you will angle the thrust line to the left as the firewall is the base for measurements. Many different combinations of washers can be used to bring the thrust line into tolerance. You will have to replace the motor mount bolts with ones that are the correct grip length. The drawing shows the factory desired thrust angles. A perfectly straight fuselage and motor mount should not need any adjusting washers. That being said, I would imagine there are very few aircraft that have not had an incident or two or have repaired motor mounts. It does not take much of an incident to tweak the parts and without a factory fuselage or motor mount jig it would be difficult to make it perfectly straight again. The engine thrust line can have a major affect regarding aircraft rigging issues. It is easy to check engine thrust line angles with a digital level and protractor.
N2709P
 
I have rebuilt 5 Super Cubs that had never been apart and installed numerous Thrustline kits as well as disassemble several PA16, 20 and 22s and never found the washer stacked to change any angles. I always figured they were an insulator of sorts between the galvanized firewall and the steel engine mount. I have also jigged more Piper fuselages than I care to remember and they are all over the place, wrecked or factory original. Have to use a plate at the tailpost because they are all a bit left or right of center. Also discovered that wing incidences are all over the place. That is why the Thrustline mod doesn't work on all Super Cubs and some airplanes are faster than others. I have always been able to rig any rag and tube Piper to fly hands off using Piper's rigging data and no trim tabs. Worked on a Cardinal many years ago that would not rig and finally figured out they had installed the Lord mounts at the wrong position and once installed correctly it rigged out with the ball in the center.
 
Thanks all. On the lower two engine mount to firewall mount points my '55 22-150 had two stacked thin steel washers of what I'd estimate to be maybe 3/32" total each stack. On the upper two mount points had one fiber at what I think was around the same thickness.. (rough estimate, would have to check again at the hangar). I will say that my mount had a noticeable sag to the upper two arms of the mount. I've since had it rebuilt by AWI/AMI and is nice and straight now, though my wallet is a bit lighter since they had to replace nearly every tube. :D

I will go back with new fiber and also check the thrustline. Any tricks to ball park it before we get the engine mounted?? Maybe mount a flat plate to the engine mount once the mount is on? Or an engine length bar?


Also I'd imagine it'd take quite a bit of washer stacking to appreciably modify the thrustline, no? Though I guess the distance arm from the firewall to the crank pulley is maybe 2.5-3ft?


Pretty weird that Piper excluded them from the drawings!
 
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Jason, I would install the mounts and engine without any washers. Once the engine is mounted, put one leg of an 18 inch carpenters square against the firewall and the other at the aft section of the upper case split line. You can use a protractor to measure the angle between the square and the case split line. Should be 2 degrees right angle. Use an 8 inch digital level along the upper case split line. This should be 4 degrees down angle. These measurements will give you the thrust line of your engine to airframe. If it is out of tolerance, you can place washers as need to improve the thrust angle. Make sure that you have properly torqued the engine mount rubbers prior to checking the angles. It takes about 5 minutes to check with the upper cowling off. If you need more than a washer or two to bring it into line, you probably have something bent pretty good. Rebuilt motor mounts are a common issue. Some jigs are not so accurate, if they jig them at all.
N2709P
 
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I check firewall to zero and then put the digital level across the two rocker covers if the engine is mounted. If not put the firewall side of the mount on a flat surface and being it is a conical mount the digital level should give you the angles when layed on the engine conical mount washers.
 
My Tri-Pacer engine mount appears to be twisted/bent down and counter clockwise as viewed from the pilot seat. The angle is 6.1 degrees down on cylinders 2, 4 and 4.1 degrees down on cylinders 1, 3, when referenced to the firewall. When you stand in front of the plane and look through the nose bowl holes, the cylinders slope down to the right a couple degrees. I rechecked the torque on all my conical bushings to 40 inch pounds, then tightened the upper pilot side to 60 inch pounds and it raised the engine about 3/16" as measured at the front mounted oil cooler gap to the nose bowl inlet. I can't see any bulges or bends in the engine mount tubes, but it must be there. Is it possible to adjust this misalignment out with washers under the lower left engine mount at the firewall?
 
Piper SL 349 allows the mount bolts for the rubber bushings to be torqued to 40”#’s rather than a specific linear measurement. If the recommended torque does not align the engine in the mount properly, either the rubber bushings need to be replaced or there is an issue with washer placement or the mount itself. Attempting to correct for a motor mount that is out of alignment by over or under torquing bushing bolts or adding washers between the bushings and engine is probably not the best solution. The welding shop in Wisconsin that bought a well known shop has serious issues with production. Their quoted cost to rebuild my motor mount that had a compression bulge on one leg was more than the cost of a new Univair mount. A lot of these airframes have been damaged in their lifetime. It might be acceptable to use a washer between the mount and firewall to correct minor powerplant alignment discrepancies.
N2709P
 
Hi again,

Piper SL 349 is Interesting. It doesn't read like there's rattle room to adjust, 40# it is.
SL-349.jpg
 
I would suspect the engine mount rubbers. I have pulled way too many that looked fine but were elongated. As far as 40 inch lbs of torque vs 1.84" of distance, from my experience they come out the same. The AN8-44 with an AN310-8 nut and the Lycoming washer come out perfect every time.

IMG_20190911_173431.jpg
 
Bushings going bad is a common issue as is engine sag. Easy to spot on preflight as the oil cooler or spinner starts to rub on the cowling. Seems to me I remember hearing about it happening mid flying season to a guy and he simply tighten the top nuts about two turns which corrected the problem until he had a chance to replace the bushings. Ben a while so not quite sure who that was.
DENNY
 
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