Rear Suspension Rebound Snubbers

Scorpio / Scorpio Cosworth Discussions - Questions, problem resolution, general talk, technical tips and modifications.
brokencase
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Rear Suspension Rebound Snubbers

Post by brokencase » Thu Feb 08, 2018 7:33 pm

I'm looking for a good picture of the original rebound snubbers for the Scorpio. They are inside the rear springs.
I was going to try to 3d print them in 90 duro polyurethane. But I need a good picture to model them in CAD.
If someone has one laying around and could maybe take some dimensions off of it that would be great.

Ed Lijewski
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Re: Rear Suspension Rebound Snubbers

Post by Ed Lijewski » Fri Feb 09, 2018 1:23 pm

Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!

brokencase
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Re: Rear Suspension Rebound Snubbers

Post by brokencase » Mon Feb 26, 2018 12:08 am

Rebound model is made. It will take 16 hours to print one.
I'll take some pics once I get them mounted in the car
https://www.thingiverse.com/thing:2806986

Ed Lijewski
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Re: Rear Suspension Rebound Snubbers

Post by Ed Lijewski » Mon Feb 26, 2018 7:35 am

Nice.

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Re: Rear Suspension Rebound Snubbers

Post by Ed Lijewski » Wed Feb 28, 2018 6:09 pm

What do your current ones look like?

I just took these pics of mine ((150K miles). How/why would yours need to be replaced?

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brokencase
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Re: Rear Suspension Rebound Snubbers

Post by brokencase » Sun Mar 04, 2018 11:18 pm

Ed, your pictures show that your rebounds are gone. They probably totally disintegrated.
What your pictures show are the metal pedestals that the rebounds mount to. The rebounds pop onto the "stud" in the center.

I've printed out the new ones, I just did not have opportunity to mount them this weekend because I was without power due to the storm.

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Re: Rear Suspension Rebound Snubbers

Post by Ed Lijewski » Mon Mar 05, 2018 8:22 am

Aha; I get it. Thanks for the enlightenment.

The apparent similarity of the cone shape in your Thingiverse rendering and the snubber supports suggested that was what you were printing.

So, I'm a buyer of a set if your prototypes work as intended.

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brokencase
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Re: Rear Suspension Rebound Snubbers

Post by brokencase » Mon Mar 05, 2018 1:33 pm

Just an FYI, the ones I printed are actually a little smaller that the originals (diameter wise). I did this in the hope that I can squeeze them through the coil spring too ease installation. Nonetheless, I believe they are slightly more firm than the originals to make up for this difference (but they not 100% solid). This is the plan anyway, but we will see how it goes. One minor concern I have is if I will be able to snap it over the "stud". I have a 16mm hole that I measured off of the original, but the new polyurethane rebounds don't stretch as easily as the original foam units in this area. I might have to do a razor "cross cut" to allow it go over the stud.

brokencase
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Re: Rear Suspension Rebound Snubbers

Post by brokencase » Mon Jun 04, 2018 8:46 pm

I wanted to show the creation and installation of the rebounds. At first I thought installation would be
impossible. But with a little ingenuity all went pretty easy. Took about 1/2 hour.

Here is what it looked like while printing... Note the partial 27% infill. The material is 90 durometer polyurathane.
If I printed them solid it would have been as hard as a shopping cart wheel. By printing with the light matrix inside
the final resiliency is similar to that of the original rebounds (which you will see below shortly).

Image

Here is the finished print. I can't remember how long the print was. It was around 15 hours I let it run overnight for each one.

Image

Now the tricky part. Installation. I pulled the bottom hole dimension from the original rebound, but when I got under the car
and saw how large the "stud" was on the pad I realized I had to do a razor cross cut around the hole to allow it to get over the "stud bulb".
Here you can see two of the cuts I made as I squeeze it a bit. You have to realize the "matrix core" is surrounded by an outer "surface skin" that is solid. That outer surface does not want to stretch so easily. This is how it is different than the foam original rebounds.

Image

I then applied some Permatex gray silicone. This was to aid in in getting the hole over the "stud" and also to dry and glue the rebound in place.

Image

I then squeezed the small end between the spring coils...by hand muscle...and the help of a little grease on the sides of the rebound.

Image

Followed by some vise grip action on the big end. It then just popped into the inner spring area. It looks soft and squishy, but trust me, it is not! It is definitely not as soft as the original rebounds, I was really worried that I would not be able to get it through the coils.
One item worth mentioning.. Because the inner infill is a cubic structure, the firmness is ansiotropic in nature. It is easier the squish the rebound sideways to get it between the spring coils, but it is much more ridged in the longitudinal axis (the working direction). Which is what we desire. This was planned when the part was designed. I had printed little test cubes of polyurethane at different infill densities and geometries to explore these options beforehand.

Image

Once inside I pushed the hole up against the nub and then pried a little on the bottom of the rebound with a screw driver and it popped over the stud and it set firmly into place. Fit perfect!

Image

Here is what is left of the old rebound in place on the driver's side...

Image

Here are the remnants of the old rebounds. They are a polyurethane "foam" that Ford likes to use. The body mounts on my Sport Trac were made of something similar (although more ridged than these). I had to change those out too after they were ten years old. I think the oxygen in the air reacts slowly over time with the polyurethane foam. Will this happen the new ones? I doubt it. The original foam has very thin cell wall membranes. The 3d printed part is made up of thicker extruded strands that I believe will last much longer. Time will tell.

Anyhow... Notice the slick little trouble light. $10 off of ebay and I'm loving it.
USB charges, folding COB led with a magnetic base. Illumination worked well for all the photos! The only downside is that it is plastic. Might break at some point...

Image

FWIW - I did another 3d print in polyurethane. An improved jack pad for my Harbor freight aluminum jack.
This was printed "solid". It took 27 hours to print. Yeah, seems crazy but it's a nice jack pad.
I made a parametric jack pad model that allows you to specify the jack pad dimensions and wheather you want a single slot or cross slot (or make it flat like mine). I will upload that up to Thingiverse.com shortly.

Image

So there you have it. This 3d printing stuff is going to change the world. I know it is changing mine.
With the crowd sourcing, the number of models on Thingiverse (and other 3d sites) are growing exponentially.

Pay particular attention to the parametric models. Search Thingiverse for "parametric" OR "openscad"
These are generalized models where you specify the dimensions of your particular need. These cover wide applications and I think are the real game changers.

Also be sure to search Thingiverse.com for "automotive". It will blow you away.
Last edited by brokencase on Tue Jun 05, 2018 7:38 pm, edited 1 time in total.

brokencase
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Re: Rear Suspension Rebound Snubbers

Post by brokencase » Tue Jun 05, 2018 7:16 pm

The question that naturally arises is.. Does having the rebounds restored really mean much in terms of normal driving?
How often do rebounds get used?

It was not until I had to replace the rear half shafts last winter that I noticed the rebounds were deteriorated. However last year I did a long trip up to the Poconos with a full load (four passengers, luggage, two road bikes on a trailer hitch carrier). In the course of the trip, there were one or two occasions of hitting some bumps and the rear suspension bottoming out and hearing a tire rubbing something. I didn't think much at the time and I had not yet replaced the rear shocks. But looking back in hindsight I can easily put 2 and 2 together...it was the lack of the rebounds.

However on my commute I think I noticed a real difference. It is under two different circumstances.

In one case I cross a road that has a very pronounced crown and deep drainage swails on both sides. I usually take this at a pretty good clip. It's a stout "double bump". I can confidently state that the car feels much more refined and graceful as I traversed across this with the new rebounds installed.

The second case was on tight turns where heavy body roll is induced. I think if your "driving sporty" you can easily get the side opposite of the turn fully compressed down to the rebound. I purposefully did this today and it does feel different. I don't know how to describe it but to say it feels more refined.

I think maybe I'll put some little balls of clay on the bottom of the rebounds and maybe I can get confirmed proof of what I believe in my subjective mind is actually occurring...but in the meantime I have peace of mind...

Ed if you want a set let me know. $25 with shipping. Keep in mind It takes two days for the machine to print them. Send me a private email to let me know.
Last edited by brokencase on Wed Jun 13, 2018 8:38 pm, edited 1 time in total.

Ed Lijewski
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Re: Rear Suspension Rebound Snubbers

Post by Ed Lijewski » Tue Jun 05, 2018 7:44 pm

Just wondering... Re working space to insert the rebound did you remove the lower shock bolt to get maximum spring extension?

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brokencase
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Re: Rear Suspension Rebound Snubbers

Post by brokencase » Tue Jun 05, 2018 8:38 pm

Nope, just jacked the car up and let the wheels hang like when I did the half-shafts. I don't know if disengaging the shocks is needed as I was able to get them in without doing so.

brokencase
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Re: Rear Suspension Rebound Snubbers

Post by brokencase » Tue Jun 05, 2018 9:25 pm

You know it is an epiphany, growing older and observing the advances of technology.

Two years ago I bought a big 3" diameter rod of black 85 durometer polyurethane rod about 2 ft long. Bought it off of ebay for around $50.
I figured I could turn on the lathe any kind of bushing I would ever need in the foreseeable future.

Let me tell ya...turning polyurethane on the lathe sucks. You actually have to grind it. Its a real mess.

I only made a couple of things out of that rod. One was a rebound for the front shock on the Sprite that mounts to the body. I still need to make one for the other side. In this case I actually band sawed it out rough and ground it to shape by hand on the bench grinder.

Another thing I made was the steering column grommet that goes on the firewall of the Scorpio. My original had split into two and the steering wheel went all sloppy (better check yours!). In this case I turned it on the lathe and did some grinding with a dremel attached to the lathe. It was a PIA to do, but it came out OK.

The last thing was my brother needed something quick and dirty for an exhaust support. I just hacked out a piece for him on the band saw.

I think I still have a foot of that material left and I will probably never use it now that I can 3dprint polyurethane. It takes longer to 3d print something, but I have learned to live with that. Let the machine do the work and wake up next morning and it is done.

Ed Lijewski
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Re: Rear Suspension Rebound Snubbers

Post by Ed Lijewski » Wed Jun 06, 2018 7:39 am

brokencase wrote:
Tue Jun 05, 2018 8:38 pm
Nope, just jacked the car up and let the wheels hang like when I did the half-shafts. I don't know if disengaging the shocks is needed as I was able to get them in without doing so.
It occured to me to ask as in changing three sets of shocks in the last year I remembered that on installing new ones needing to jack up the arms ~ 1"-2" to insert the lower bolts.

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Descartes: "Cogito Ergo Sum"
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john keefe
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Re: Rear Suspension Rebound Snubbers

Post by john keefe » Thu Jun 07, 2018 5:20 pm

Wow. That is pretty cool.

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