Transaxle/motor mount again

Dr.Jeff

True Classic
Overall, looking at the discussions we've had about this mount, several ideas have come up for potential "improvements". It would be nice to gather all those ideas into a revised design that perhaps could be produced in a limited run. A couple ideas that come to mind off hand might be:

1) Using a more durable material for the 'rubber' portion. I'm thinking one of the more compliant duros of urethane would be good. The other thread described some tips for making a mount with this material.

2) With the new filler material used to construct it, we could also eliminate the "voids" (air gaps or openings) like the stock mount has, to lessen any chance of it over compressing/collapsing.

3) Either repositioning the "center pin" to slightly raise the drivetrain, or maybe even come up with a practical means of making it adjustable height (other than slotted holes). Or would using a material that won't sag (#1 above) preclude the need for this?

4) regarding the 'center pin', @Mxgrds made a good point in post #29 above. A larger surface area for the interface between the pin and the filler material will reduce the pin's tendency to dig into it. However I've noticed most of the mounts I've had include a 'bushing' around the center pin that increases it's OD considerably. Although sometimes it isn't apparent that bushing is there until you begin to deconstruct the whole thing; often the rubber is cast over the edge of it so it cannot be seen. But maybe something even better can be done. In the prior thread we discussed adding extension "arms" to the center pin, going further out into the filler material to achieve this. That will also improve the adhesion of the urethane to the metal components.

5) The concept of a torque arm added to the lower mounting of the trans has been found beneficial in preventing trans damage. So why not incorporate the ability to add one into the revised lower mount design. Such as adding a tab to one end, similar to what @GregS showed in post #35. I'm thinking something shaped into the flat plate of the mount, akin to the exhaust hanger extension arm on some stock mounts (but much shorter). Then the user can decide to easily add the torque arm if desired.

6) Does it need any further support to prevent 'twisting' from side to side (e.g. added stability)? I'm thinking of the idea of side reinforcement plates that was brought up in the prior thread (reference link is needed here).

7) #6 brings up a related question I think we previously addressed to some extent; the ability of the drivetrain to 'rotate' about the center pin of this lower mount. The engine moves fore/aft with the torque of acceleration/deceleration, which will "pivot" or rotate around the lower mount. The 'dogbone' is intended to control this, as would adding a torque arm to the lower mount (see #5). But I believe the lower mount is intended to offer some compliance to allow for these 'rocking' movements. With the soft rubber filler material in a stock mount there is plenty of flexibility to allow the pin to twist within the rubber. But with a more firm material (like urethane) there will be less flexibility. So is more allowance for 'pivoting' needed (e.g. a bearing around the center pin)? Or would that just counter the effects of the dogbone and torque arm?

Other thoughts, ideas, suggestions???
 

Ulix

True Classic
Jeff,

I think the main challenge will be to make the mount stiff enough to prevent sagging, yet compliant enough to do its job of NVH insulation on a street car without compromise. For instance, I believe that the voids are likely important for that.
Mark Plaia used to fill the void with silicone and IIRC he told me that the mount transmitted noticeably more vibration. But that was almost 25 years ago. :rolleyes:

Regarding your point 7): you can easily calculate the amount of rotation. Say you had a worn out dogbone and your engine would move 5mm at the bone, the angle of rotation would be roughly 0.00nothing degrees. So nothing to worry about there.
The torque arm would be great to have.

I will buy two of your mounts!
 

Mxgrds

True Classic
Jeff,

I think the main challenge will be to make the mount stiff enough to prevent sagging, yet compliant enough to do its job of NVH insulation on a street car without compromise. For instance, I believe that the voids are likely important for that.
As long as the voids are not positioned under the rod!
 

lookforjoe

True Classic
I think if an additional torque mount is added, it needs to attach at the forward face - so that the two torque mounts work together. All the Volvo setups I am familiar with operate this way - upper torque mount attached to firewall/head, lower torque mount attaches to bell housing/block connection & forward lateral nose section.
 

Dr.Jeff

True Classic
As long as the voids are not positioned under the rod!
And that is another issue we noted previously; many of the replacement mounts have the voids in different locations, some almost 90 degrees to either side of the pin and others almost directly under the pin. That alone may account for much of their lifespan differences.
 

ArtBasement

Erwin Timmers
OK, so here's my show and tell, because I want this car back on the curvy roads by tomorrow. My plate was drilled through and a 22mm bar was welded in on the rubber side only. The bar had 2 step downs to 16mm where it goes through plate, and where it goes through bushing/rubber. I was able to cut the weld only and pop the bar out of the plate. I didn't want to try and separate the rubber from the bar. I flipped the plate and welded it back up. Welding on the rubber side was very tough. It was difficult to get the nozzle aimed at the plate, because of the rubber in the way. So I decided to also weld it from the back. Constantly cooling stopped the rubber from melting. Hope it all fits back tonight
 

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Dr.Jeff

True Classic
I think the main challenge will be to make the mount stiff enough to prevent sagging, yet compliant enough to do its job of NVH insulation on a street car without compromise.
I agree. I guess the best approach would be to make several examples using various duros and test them. But I would not want to go through all of that for such a limited production run (experience has taught us that only a few of such upgraded parts will actually sell). That is why I guesstimated that one of the softest duros of urethane might be a good choice. It should offer enough compliance to have decent NVH management, but still firm enough to hold up fairly decent (hey, anything would be better than most of what's out there now).

This is also why I posed the notion in item #6. I believe it was @lookforjoe that did something like this but I can't find his pics now. Basically the idea is to add plates to the flat sides of the rubber to prevent it from bulging. Depending how you do it, it may be possible to improve the lifespan of the mount without a big increase in its "stiffness" (compliance).
 

Dr.Jeff

True Classic
Regarding your point 7): you can easily calculate the amount of rotation. Say you had a worn out dogbone and your engine would move 5mm at the bone, the angle of rotation would be roughly 0.00nothing degrees. So nothing to worry about there.
I vaguely recall that was what we deduced previously also - just wasn't sure when I wrote the earlier post.
So if it does not need to rotate around the center pin, then some other improvements that were suggested before can be done as well.

For example the surface area of the center pin can be significantly increased relative to the rubber it contacts. Rather than increasing the diameter of the pin, it was suggested to make the pin effectively 'wider' (longer?) by adding "wings" or an "umbrella" to it. In other words it does not need to be a round pin, it can be extended in either direction to make it more of a flat surface riding against a fuller expanse of the rubber.

One idea from @Mxgrds is to extend up from the end of the pin to a plate that rides on top of the rubber. This can be done to an existing mount (I think he also had another illustration that might be better to visualize it):
15ABBD76FDB9.png


Or if you are making a mount by casting it with a new material, then the extensions can be added to the pin internally, something like this:
EliP.jpg


This should improve the life of the rubber (less sag) without too much adverse effect on its performance (NVH compliance).
 

Dr.Jeff

True Classic
OK, so here's my show and tell, because I want this car back on the curvy roads by tomorrow. My plate was drilled through and a 22mm bar was welded in on the rubber side only. The bar had 2 step downs to 16mm where it goes through plate, and where it goes through bushing/rubber. I was able to cut the weld only and pop the bar out of the plate. I didn't want to try and separate the rubber from the bar. I flipped the plate and welded it back up. Welding on the rubber side was very tough. It was difficult to get the nozzle aimed at the plate, because of the rubber in the way. So I decided to also weld it from the back. Constantly cooling stopped the rubber from melting. Hope it all fits back tonight
Nice job. ;) Very clean welds in that tight space between the rubber and plate. Be sure to show us how high the trans sits with this configuration.
 

Mxgrds

True Classic
Picture 1 the voids under the rod don’t really help once under pressure.
picture 2 and 3 making use the top part of the rubber and more rubber to carry the weight of the engine and still allow momevement is all directions.The voids filled with rubber. D23D424F-086E-442D-8FFB-163DF6C5C78D.jpegE48E0D4C-18D7-466A-9754-BEE26BDF01DA.jpeg1123E32B-6DCE-4DBD-B1CB-76FF064D0835.jpeg
 

Ulix

True Classic
I did some measuring today.
I wanted to see how much difference are in the different mounts that I have.
None of them is really crushed, so I think a comparison makes sense.
The goal was to measure the height between the mounting plane of the mount on the crossmember to mounting holes in the tranmission plate (of the mount).
The transmission hangs on this plate, so a smaller distance is good, it lifts the transmission higher compared to the crossmember.

So I opened my vise to the distance between the center of the bottom mounting holes and placed the mount on the jaws. The jaws are now the reference plane, they represent the crossmember. The mount sits upside down from its normal orientation in the car.

AA42C637-633B-4A10-B4AE-35BB5C669934.jpeg7C78654A-1725-400E-B96E-B8635410699A.jpeg3861C065-D89E-42DA-BD79-2FE8B404686B.jpeg

I then measured from the reference plane to the top edge of the holes in the plate (bottom edge when mounted in the car). The transmission bolts will rest on the bottom of the plate holes, so that is what I chose as a measuring point.

B16A0A48-19FE-4756-A289-841DF904B7B6.jpegA1B97CB5-F16C-425A-AEBF-E7169EA4AE11.jpeg

I then took the average of these two measurements to get the distance.

Here are the results in mm:
31.25
31.5
35.0
35.75
38.5

So we have a difference from best to worst of 7.25 mm!
I would say this makes all the difference and explains why some people don’t have a problem and some do, even though their mount looks ok.

Based on this, I would deduce:
- if the rubber on your mount keeps failing, you need a better mount material
- if your material has been holding up, you may only need to move the holes in the plate
 

Dr.Jeff

True Classic
@Ulix, well done. Interesting info. I guess I'm not really surprised there is a lot of variance, typical of many parts for such old vehicles. When you consider a 5-speed only has around 10mm or so gap between the crossmember and axle/CVJ, then that variance is significant.
 

berserker0815

Low Mileage
I did some measuring today.
I wanted to see how much difference are in the different mounts that I have.
None of them is really crushed, so I think a comparison makes sense.
The goal was to measure the height between the mounting plane of the mount on the crossmember to mounting holes in the tranmission plate (of the mount).
The transmission hangs on this plate, so a smaller distance is good, it lifts the transmission higher compared to the crossmember.

So I opened my vise to the distance between the center of the bottom mounting holes and placed the mount on the jaws. The jaws are now the reference plane, they represent the crossmember. The mount sits upside down from its normal orientation in the car.

View attachment 37318View attachment 37319View attachment 37320

I then measured from the reference plane to the top edge of the holes in the plate (bottom edge when mounted in the car). The transmission bolts will rest on the bottom of the plate holes, so that is what I chose as a measuring point.

View attachment 37321View attachment 37322

I then took the average of these two measurements to get the distance.

Here are the results in mm:
31.25
31.5
35.0
35.75
38.5

So we have a difference from best to worst of 7.25 mm!
I would say this makes all the difference and explains why some people don’t have a problem and some do, even though their mount looks ok.

Based on this, I would deduce:
- if the rubber on your mount keeps failing, you need a better mount material
- if your material has been holding up, you may only need to move the holes in the plate

Well done Ulix!
Hope this solves our problems...
 

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fiatfactory

Steve Cecchele
Nice work Ulix.

Based on your method, I set up a similar test rig, and with as much accuracy as possible measured a new OE Fiat mount without an exhaust stay bracket... Fiat simply specify one number for a mount with an exhaust bracket, and another number for mounts without an exhaust bracket.
20201012_153518.jpg


Measuring from the reference line up to the top of the holes in the mounting plate, I got 29.2mm and 32.0mm, averaged that's 30.6mm.(edited the pic for a better one with some light)


SteveC
 
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Dr.Jeff

True Classic
I got 29.2mm and 32.0mm, averaged that's 30.6mm
Here are the results in mm:
31.25
31.5
35.0
35.75
38.5
Looking at these numbers, and given that the lower the measurement means the higher the trans sits, then with a new mount the trans sits around 4mm higher than the average "good" used aftermarket ones. [Hope I understood what everyone said correctly.] I recall in the past a gap of around 10mm (CV to subframe) was thought to be "normal"(?). If so then even a slightly used mount loses 40% of that clearance. Easy to see why all of my lower subframe cross members have signs of 'grinding' damage at that spot.
 

fiatfactory

Steve Cecchele
Looking at these numbers, and given that the lower the measurement means the higher the trans sits, then with a new mount the trans sits around 4mm higher than the average "good" used aftermarket ones. [Hope I understood what everyone said correctly.] I recall in the past a gap of around 10mm (CV to subframe) was thought to be "normal"(?). If so then even a slightly used mount loses 40% of that clearance. Easy to see why all of my lower subframe cross members have signs of 'grinding' damage at that spot.

I also just measured up a fresh out of the packet AKRON / MALO branded lower mount, application listed on the bag tag as Fiat 128 lower mount, it measures 34.6 and 34.4mm for an avearge of 34.5mm

So based on the sample size of 7, I see three statistical groupings.

30.6mm - 31.5mm average (3)
34.5mm - 35.75mm average (3)
>38.5mm (1)

SteveC
 

Ulix

True Classic
Jeff,
I think that the variation in my results comes mainly from manufacturing differences between the mounts, not from wear.
This is supported by Steve's last data point of a new mount measuring 34.5 mm.
 

fiatfactory

Steve Cecchele
Jeff,
I think that the variation in my results comes mainly from manufacturing differences between the mounts, not from wear.
This is supported by Steve's last data point of a new mount measuring 34.5 mm.

I would tend to agree given the quite tight statistical groupings.

To further confirm the hypothesis, I'd like to know the actual raw measurements of your mounts. I would like to know that, if like me, you found the 34.5 - 35.75 group had several mm difference from one side to the other, and if the 30.6 to 31.5mm group had almost the same numbers left / right as I found.... I think that would confirm that there are two different mounts to suit the two different engine tilts of the sohc motor, 128/uno etc etc at approx 18/20 degrees tilt, and the X19 all alone at 11 degrees tilt

SteveC.
 

Ulix

True Classic
Steve,
here you go, in the same order as above:
30.0 32.5
31.5 31.5
32.0 38.0
35.5 36.0
36.0 41.0
 
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