Renewing NOS cab bushings-- is that possible?

[coachgeo]

.... Be careful with NOS rubber bits from the surplus scalpers (20 y/o rubber is crap whether it is on a truck or on a shelf) and they want insane amounts of money for the complete sets to do both sides.
....

Ive got some NOS bushings to use..... bought before the prices went nuts. Is there any way to renew the before install?? like soak them in xyz?? or heat to "ohfawk" temperature while in a bath of oil??? orrr???

 

[coachgeo]

doing some research came across some stuff with some interesting info

Rubber renew and long term effects

Rubber renew and long term effects

forums.sohc4.net

How To Restore Natural Rubber Products

Natural rubber is made from the sap of the rubber tree, which is drained off, heated, and formed into rubber parts. Rubber has many uses; it is water-resistant, flexible, strong, and elastic. That said, over time natural rubber will tend to dry out, stiffen, and crack. It is often cheaper and...

sciencing.com

 

[Awesomeness]

The bushings aren't made of rubber - they are polyurethane. Unfortunately there isn't much you can do for them. The polymers break down over time, and the material degrades. The way the bushings are used, with a lot of weight squeezing the bushing and requiring it to have a lot of tensile strength to resist tearing apart from the forces spreading it out, you can't "rejuvenate" that.

The NOS bushings seem to be hit or miss, depending on many factors, such as the batch they were made in, how old they are, what temperature and humidity they were stored in, etc. I have some that I bought to take measurements off of that seem fine (though I've never installed them). I also have one that broke apart in shipping, before it even got to me!

 

[Guruman]

Couldn't we just cast our own out of new poly? Maybe using the NOS ones to make silicone molds? I might be willing to give this a go and make a few sets, anyone have some NOS ones for cheap?

 

[Awesomeness]

Couldn't we just cast our own out of new poly? Maybe using the NOS ones to make silicone molds? I might be willing to give this a go and make a few sets, anyone have some NOS ones for cheap?

Yes, you can. I make the sway bar bushings that way. However, it's not cheap or easy. You have to buy a bushing to get measurements (I don't cast directly from an OEM one, because both the mold silicone and polyurethane castings shrink, so you have to compensate), as well as get a vacuum degassing setup and pressure casting chamber. The material costs (only) for something this size are probably about $75-120 for silicone mold rubber, and $15-25 per bushing (including color dye and UV inhibitors). You can cut corners if you're on a budget, but the castings aren't nice/right (e.g. small fitment issues that require trimming each by hand or muscling them to fit, crude aesthetics, bubbles and imperfections that can create stress points that fail sooner, no expensive UV inhibitors but they will break down outdoors sooner, etc.). And then, after all that, you have to do it a second time for the other bushing of the top/bottom pair.

I've been "working on" some cab mount bushings, for longer than I'm proud of. We were preparing to move, then moved last year, and am now stuck in a rental house without a good shop until my new house is built (which is seeing all sorts of delays because of the pandemic). I finally got all my molding/casting stuff set back up a couple months ago, and I'm hoping to have them soon, though.

 

[Third From Texas]

Yes, you can. I make the sway bar bushings that way. However, it's not cheap or easy. You have to buy a bushing to get measurements (I don't cast directly from an OEM one, because both the mold silicone and polyurethane castings shrink, so you have to compensate), as well as get a vacuum degassing setup and pressure casting chamber. The material costs (only) for something this size are probably about $75-120 for silicone mold rubber, and $15-25 per bushing (including color dye and UV inhibitors). You can cut corners if you're on a budget, but the castings aren't nice/right (e.g. small fitment issues that require trimming each by hand or muscling them to fit, crude aesthetics, bubbles and imperfections that can create stress points that fail sooner, no expensive UV inhibitors but they will break down outdoors sooner, etc.). And then, after all that, you have to do it a second time for the other bushing of the top/bottom pair.

I've been "working on" some cab mount bushings, for longer than I'm proud of. We were preparing to move, then moved last year, and am now stuck in a rental house without a good shop until my new house is built (which is seeing all sorts of delays because of the pandemic). I finally got all my molding/casting stuff set back up a couple months ago, and I'm hoping to have them soon, though.

Yeah, I'm going to take a stab at it just because I need three sets of bushing for my A1R cab. I think I can justify the expense in my case (not so much that I want to do it but there simply are no other alternatives). I don't mind paying a fair price for something someone actually makes, but at some point it can justify diy.

I want to tinker with doing it because I also need upper swaybar grommets and swaybar bushings on both my truck and the M1082 (I know they are the other size). Nobody is making the uppers nor cab bushings as you know. I'm going to start with squishy molds and see where it leads. I started a thread on the topic somewhere around here last year that includes the material supplier, shore/durometer info, etc.

I want to make sets of everything I need on the truck/trailer as well as a box of spares. I've no interest in production, but if it works I plan to freely share all the necessary info. I've been dragging my feet until my buddy gets his new 3D printer to crank out the blanks for the upper swaybar bushing molds.

 

[Awesomeness]

Yeah, I'm going to take a stab at it just because I need three sets of bushing for my A1R cab. I think I can justify the expense in my case (not so much that I want to do it but there simply are no other alternatives). I don't mind paying a fair price for something someone actually makes, but at some point it can justify diy.

I want to tinker with doing it because I also need upper swaybar grommets and swaybar bushings on both my truck and the M1082 (I know they are the other size). Nobody is making the uppers nor cab bushings as you know. I'm going to start with squishy molds and see where it leads. I started a thread on the topic somewhere around here last year that includes the material supplier, shore/durometer info, etc.

I want to make sets of everything I need on the truck/trailer as well as a box of spares. I've no interest in production, but if it works I plan to freely share all the necessary info. I've been dragging my feet until my buddy gets his new 3D printer to crank out the blanks for the upper swaybar bushing molds.

It's totally doable, and needing several takes some of the sting out of the cost, though I recommend against the "squish mold" approach. The squishing action means you are always putting stress on the mold and casting, resulting it parts that are often deformed, as well as trapping bubbles inside. If the parts have a flat side, which the bushings all do, just have a mold that is open on top, overfill it, then trim the cured bushing down to size on that flat face.

 

[Third From Texas]

It's totally doable, and needing several takes some of the sting out of the cost, though I recommend against the "squish mold" approach. The squishing action means you are always putting stress on the mold and casting, resulting it parts that are often deformed, as well as trapping bubbles inside. If the parts have a flat side, which the bushings all do, just have a mold that is open on top, overfill it, then trim the cured bushing down to size on that flat face.

Gonna take a stab at this in a couple weeks. Ordering in the materials.

What do you recommend as a material for the mold?

No 3D printer here, but I have a set of OEM cab bushings that I can cast a mold. I've only messed with this sort of thing once for a single piece I needed and I actually just used plaster (but I destroyed the mold taking the item out). I know I'll need a release spray at pour and I'm only gonna be making three sets. I know most reusable molds will have a lifespan of x number of uses, but I wouldn't mind making a s[pare set for down the road.

 

[Guruman]

Gonna take a stab at this in a couple weeks. Ordering in the materials.

What do you recommend as a material for the mold?

No 3D printer here, but I have a set of OEM cab bushings that I can cast a mold. I've only messed with this sort of thing once for a single piece I needed and I actually just used plaster (but I destroyed the mold taking the item out). I know I'll need a release spray at pour and I'm only gonna be making three sets. I know most reusable molds will have a lifespan of x number of uses, but I wouldn't mind making a s[pare set for down the road.

a flexible silicone mold wouldn't fall apart like plaster.

 

[Awesomeness]

Gonna take a stab at this in a couple weeks. Ordering in the materials.

What do you recommend as a material for the mold?

No 3D printer here, but I have a set of OEM cab bushings that I can cast a mold. I've only messed with this sort of thing once for a single piece I needed and I actually just used plaster (but I destroyed the mold taking the item out). I know I'll need a release spray at pour and I'm only gonna be making three sets. I know most reusable molds will have a lifespan of x number of uses, but I wouldn't mind making a s[pare set for down the road.

If you're not going to make too many of them (e.g. <12), a cheaper tin-cure silicone mold rubber will do. Be careful not to tear the mold while taking the castings out, as the tin-cure silicone is not as stretchy and resilient as the platinum-cure (which costs significantly more). You'll probably need 2 of the $40 "trial kits" to make a mold that size (I don't think one would be enough). https://shop.smooth-on.com/mold-max-30

You're going to spend around $120-150 to make 4 bushings (only one type of bushing, not both top and bottom... if you want both top AND bottom, double it).

 

[Third From Texas]

If you're not going to make too many of them (e.g. <12), a cheaper tin-cure silicone mold rubber will due. Be careful not to tear the mold while taking the castings out, as the tin-cure silicone is not as stretchy and resilient as the platinum-cure (which costs significantly more). You'll probably need 2 of the $40 "trial kits" to make a mold that size (I don't think one would be enough). https://shop.smooth-on.com/mold-max-30

You're going to spend around $120-150 to make 4 bushings (only one type of bushing, not both top and bottom... if you want both top AND bottom, double it).

Thanks.

Yeah, I need three tops and three bottoms (minimum). A gallon of ECON 80 hardness, black UV tint, a can of release, and a gallon of mold 30 runs about $350-400 shipped. That's in line with what I can purchase three sets of crusty old NOS bushings That leaves me with a couple spare sets for free plus it should be enough to maybe make some upper swaybar bushings (I've never been able to find those).

Thanks again!

 

[Awesomeness]

Thanks.

Yeah, I need three tops and three bottoms (minimum). A gallon of ECON 80 hardness, black UV tint, a can of release, and a gallon of mold 30 runs about $350-400 shipped. That's in line with what I can purchase three sets of crusty old NOS bushings That leaves me with a couple spare sets for free plus it should be enough to maybe make some upper swaybar bushings (I've never been able to find those).

Thanks again!

If you're doing Shore 80A hardness, I recommend PMC-780. https://www.smooth-on.com/products/pmc-780-dry/

These thick urethane rubbers, and to lesser extent the silicone rubber, really trap a lot of air bubbles. Ideally, you need a vacuum chamber to degas them. You might be able to make do by pouring from a very high height (e.g. 3') and making a deep mold so that the bubbly rubber foam can float up and sit at the top of the mold (1/2"+) which you then cut off.

 

[BEASTMASTER]

i used some hockey pucks on mine .

 

[coachgeo]

i used some hockey pucks on mine .

have heard that more than once. @Awesomeness (an engineer) mentions 60shore for the neccissary shore you want to make them earlier in this thread. .... and according to below video..... Hockey pucks are around that. Have seen them listed in charts giving average examples of what "shore" hardness is at 60shore also

 

[GeneralDisorder]

Thanks.

Yeah, I need three tops and three bottoms (minimum). A gallon of ECON 80 hardness, black UV tint, a can of release, and a gallon of mold 30 runs about $350-400 shipped. That's in line with what I can purchase three sets of crusty old NOS bushings That leaves me with a couple spare sets for free plus it should be enough to maybe make some upper swaybar bushings (I've never been able to find those).

Thanks again!

For our style of rear cab latch you actually will need 4 bottoms - 2 for the rear cab latch, and 1 each for the front cab mounts.

The stock bushings indeed have a "use by date" as the material deteriorates over time. IDK why they use this stuff - it may be that the military wants them to be quiet and this material fills that role.

 

[Awesomeness]

have heard that more than once. @Awesomeness (an engineer) mentions 60shore for the neccissary shore you want to make them earlier in this thread. .... and according to below video..... Hockey pucks are around that. Have seen them listed in charts giving average examples of what "shore" hardness is at 60shore also

There are a number of factors at play, including the Shore A hardness. Generally, the harder materials have higher tensile strengths, so they should resist splitting and tearing under pressure better. Aftermarket polyurethane bushings that are marketed as "high performance" typically use harder materials than stock, both to provide a firmer resistance and a stronger part.

Hockey pucks will probably dry out and crack sooner than polyurethane would, but it's better than nothing if yours are totally gone.

 

[Third From Texas]

have heard that more than once. @Awesomeness (an engineer) mentions 60shore for the neccissary shore you want to make them earlier in this thread. .... and according to below video..... Hockey pucks are around that. Have seen them listed in charts giving average examples of what "shore" hardness is at 60shore also

I think you mean 80. My research landed at shore 80 for the cab bushing (I don't think Awesomeness mentioned a specific hardness in this thread). We've had this discussion in several threads here. Hokey pucks are 90 so there are very close to what is used in most HD bushings.

There are a number of factors at play, including the Shore A hardness. Generally, the harder materials have higher tensile strengths, so they should resist splitting and tearing under pressure better. Aftermarket polyurethane bushings that are marketed as "high performance" typically use harder materials than stock, both to provide a firmer resistance and a stronger part.

Hockey pucks will probably dry out and crack sooner than polyurethane would, but it's better than nothing if yours are totally gone.

Agreed. I'm not knocking those who use hockey pucks, but back in the 80's-90's when we had an off-road center here in S TX, we did a LOT of lifts. I've seen body lifts done using hockey pucks that didn't hold up to the elements well (in fact, the mechanics there used to rage on people who had "red-necked" their body lifts with pucks). Not saying that they aren't a viable solution, just saying that I'm not going to use them for the long run.

I suspect that you could even raise the cab a wee bit (help clear 53's?) with the right bushings (limitations being the usual body lift items like hoses, lines, wires, steering).

 

[Guruman]

I think you mean 80. My research landed at shore 80 for the cab bushing (I don't think Awesomeness mentioned a specific hardness in this thread). We've had this discussion in several threads here. Hokey pucks are 90 so there are very close to what is used in most HD bushings.




Agreed. I'm not knocking those who use hockey pucks, but back in the 80's-90's when we had an off-road center here in S TX, we did a LOT of lifts. I've seen body lifts done using hockey pucks that didn't hold up to the elements well (in fact, the mechanics there used to rage on people who had "red-necked" their body lifts with pucks). Not saying that they aren't a viable solution, just saying that I'm not going to use them for the long run.

I suspect that you could even raise the cab a wee bit (help clear 53's?) with the right bushings (limitations being the usual body lift items like hoses, lines, wires, steering).

Back in the day.... ( I must be getting old). I had a Jeep with a body lift made from machined aluminum pucks..... I wonder if something like that would be a (better?) option for us? Just replace the worn out rubber with aluminum. How much flex does it really need?

 

[Mullaney]

Back in the day.... ( I must be getting old). I had a Jeep with a body lift made from machined aluminum pucks..... I wonder if something like that would be a (better?) option for us? Just replace the worn out rubber with aluminum. How much flex does it really need?

.
I will be really interested to see what the guys have to say about aluminum @Guruman .

When I replaced my dried out, badly cracked (but still whole) cab bushings - there was a noticeable improvement in how my M1088 "felt" bouncing down the road. My M1089 that had one bushing completely GONE and the other in pretty bad shape was better too. Funny part is that neither one of them ride very well anyhow...

 

[chucky]

Someone brought up last time we went down this rabbit hole that they used hockey pucks and just drilled the center hole on a drill press ! All my body bushings are good but i bought a bag of them for 5 bucks at the flea market the other day and it seems doable to me!