Casting: Rear Coil Spring Bumpers - Second Generation Forum

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Casting: Rear Coil Spring Bumpers
Saturday, January 05, 2019 10:32 AM
Hey all. Posted this over at v6z24 and want to share it here too.
Somebody may want to consider doing the same. I believe this applies to all 1st and 2nd gen Cavalier.

Having never seen a new set of these bumpers available anywhere, I'm casting some.

Currently the plan is to make copies of the model, retaining shape, without the tip being hollow at the bumper end. It will have the cavity inside where the metal cap is on the original. The metal cap will not be in it though.
Casting will be Urethane 60A; https://www.mcmaster.com/8644k24

This video shows the repair of the bottom seat of the original bumper for use as the master.
https://youtu.be/S4bNdjNJGxY
It is currently clamped together for the glue to dry.

Mostly, updates will include links to videos, so everyone can see what is going on.
Please offer any suggestions, if you can think it will improve the bumpers. Such as; Should I remove the hollow tip portion (about 3/4" off the tip) of the bumper and make it more flat on the top? Should the cavity be only as deep as required to sit on the mounts button?.

I'm going to begin making the base for the model to sit on. Should begin laying on the clay in a few days.

Re: Casting: Rear Coil Spring Bumpers
Saturday, January 05, 2019 12:15 PM
These are the top ones , Right?

Currently have the bolt on coil spring spacers in my coils, had footballs inside the springs but they didn't last, ended up cutting the lower bumpers to get them in.

Looking to make my own spacers out of pipe and plate to raise the coils off the mount. Seen some guy make some out of plywood to space the springs from the top. ( Not to sure about that)

Then there is the guy on the 3rd gen that used Daystar spacers on his car....

Doug in P.R.


92 Pontiac Sunbird LE, 2.0, AT, Red / Black with Grey 149K miles. Hurricane Maria Survivor ! ( It takes a licking and keeps on ticking ! ).....in Salinas, Puerto Rico!




Re: Casting: Rear Coil Spring Bumpers
Saturday, January 05, 2019 1:22 PM
92Sunbird PuertoRico wrote:

These are the top ones , Right?
Doug in P.R.
No, these are the bottom ones. I've got a few good top ones, but will wind up making some of them too. Later on though.
Re: Casting: Rear Coil Spring Bumpers
Saturday, January 05, 2019 2:27 PM
Here is another video of the master.
https://youtu.be/bTYv2KPyEDY
Re: Casting: Rear Coil Spring Bumpers
Saturday, January 05, 2019 7:48 PM
Master is set in clay with box around it. Ready to pour side on of the mold. I'll do it in the morning.
https://youtu.be/SHnb4tLsxts
Re: Casting: Rear Coil Spring Bumpers
Sunday, January 06, 2019 4:37 PM
Pouring the first half of the mold. I didn't mix enough
https://youtu.be/FdMv8w1pZGc

And here is one where I added more silicone to fill up the box.
https://youtu.be/g0eZnLQFPZA

I'll open it up tomorrow and see what it looks like.
Re: Casting: Rear Coil Spring Bumpers
Thursday, January 10, 2019 5:14 PM
The mold came out very well. I just filled it with water to see how much it held. About 6.75 ounces. No leaks either and that was just holding it together in my hands.
I'll divide the poly/hardener by half for the two pours. There will be around 2.5 ounces of wasted poly.

I'm going to pour one this weekend. Hopefully everything turns out well.
Re: Casting: Rear Coil Spring Bumpers
Friday, January 11, 2019 12:27 PM
Looking forward to it Butch, if you could ,could you please get the diameter of the cone at the widest part with digital micrometer?

Thanks, Doug in P.R.


92 Pontiac Sunbird LE, 2.0, AT, Red / Black with Grey 149K miles. Hurricane Maria Survivor ! ( It takes a licking and keeps on ticking ! ).....in Salinas, Puerto Rico!




Re: Casting: Rear Coil Spring Bumpers
Friday, January 11, 2019 3:09 PM
Sorry Doug, I don't have a digital micrometer.
However, best I can tell it is 2-1/4 inches at the widest part, which is just above the top of the spring when the spring is seated.
Re: Casting: Rear Coil Spring Bumpers
Saturday, January 12, 2019 8:02 AM
Ok, thanks, Butch

Doug in P.R.


92 Pontiac Sunbird LE, 2.0, AT, Red / Black with Grey 149K miles. Hurricane Maria Survivor ! ( It takes a licking and keeps on ticking ! ).....in Salinas, Puerto Rico!




Re: Casting: Rear Coil Spring Bumpers
Sunday, January 13, 2019 4:21 AM
And here is the bumper after removing it from the mold.

Looks to be a success
https://youtu.be/k8S62tEPOHo

Re: Casting: Rear Coil Spring Bumpers
Sunday, January 13, 2019 8:19 AM
Looks fantastic, Butch, great job.

Doug in P.R.


92 Pontiac Sunbird LE, 2.0, AT, Red / Black with Grey 149K miles. Hurricane Maria Survivor ! ( It takes a licking and keeps on ticking ! ).....in Salinas, Puerto Rico!




Re: Casting: Rear Coil Spring Bumpers
Sunday, January 13, 2019 12:02 PM
Thanks Doug.

It's been fun and educational.
I'll take the 2nd one out of the mold later this evening. Hope it turns out at least as well as the first one.
In a couple weeks, I'll put them in the 88 Coupe for testing. Once I see they will hold up, I'll make some more.
Re: Casting: Rear Coil Spring Bumpers
Sunday, January 27, 2019 2:49 PM
I didn't get these on the car yet. Will do it this coming weekend, if I can find the time.
I'll put them in the 92 instead of the 88. I tend to drive it more than the 88.
Re: Casting: Rear Coil Spring Bumpers
Sunday, February 03, 2019 1:08 PM
They are mounted and all seems good. Did a test drive including going over uneven side road turn offs, curves and bumps. No negative effects.

Will drive a few hundred miles over the next couple weeks or so to see how they hold up.

I measured the height of the car at the rear wheel wells before I changed them out. These raised the rear of the car about 3/8-1/2 inch. Roughly the thickness of the base. The originals were worn down to nothing, so the base of them were not really holding the spring off the axle any amount.

I'll call it a success, so far anyway.
Cost quite a bit though.
Mold making rubber - $77.80
Clay (reusable) - $16.20
Casting compound (took every bit of the 1 pound size) - $44.97
Mold release (still have most of it leftover) - $17.00
Misc items - $5.00
Total $160.97

Though now with the mold made, making more bumpers will pretty much just be the cost of the casting compound and a shot or two of the mold release. However, if I buy the 10 Lbs size of the compound, the price for making more of them will probably be a little less. Though shipping 10 Lbs may cost a bit. I don't know. I'll need to order some before long, as all my cars need these replaced. 10 pounds will make 20 of them.
Attachments
Bumper Driver Side.jpg (365k)
Bumper Pass Side.jpg (368k)

Re: Casting: Rear Coil Spring Bumpers
Monday, February 04, 2019 9:54 AM
Looks good Butch, what do you figure the cost per pair would be ?


Doug in P.R.


92 Pontiac Sunbird LE, 2.0, AT, Red / Black with Grey 149K miles. Hurricane Maria Survivor ! ( It takes a licking and keeps on ticking ! ).....in Salinas, Puerto Rico!




Re: Casting: Rear Coil Spring Bumpers
Monday, February 04, 2019 4:34 PM
Probably around $60.00 a pair. But I want to get some miles on them to be sure they hold up well and are safe before I'd sell any. I'd want to get at least a few months trial and then take them out to inspect them. I'll also be doing a visual inspection on them weekly, for the time being.
Once I know all is good, I'll buy 10 Lbs of poly to make 10 sets. I'd need to keep 3 sets of those for myself, but will offer the other 7 sets up for sale. I'm considering 80 durometer. 60 feels a little softer than the originals are, but not by much.
I'll keep you posted.
Re: Casting: Rear Coil Spring Bumpers
Friday, February 08, 2019 6:29 PM
Looks Great!!

Also looks like you've cooked yourself up a real nice side job there buddy!!
God knows how many will see this and be beating on your inbox for a set.....Hahaa!!



.



Re: Casting: Rear Coil Spring Bumpers
Thursday, July 04, 2019 2:55 PM
Hey all
Just got back from NC. I'd put the 2nd set in the car before leaving.
Here is an update on them.
https://www.v6z24.com/jbodyforum/rear-spring-bumpers-t142227,start,27.html
Re: Casting: Rear Coil Spring Bumpers
Sunday, July 07, 2019 2:37 PM
Used up the poly making 5 more. Learned a lot from it. I'm pretty sure this material is excellent for these. I'll be making new molds soon and begin making larger batches.

If you'd like to see them along with some info and chatter:
https://youtu.be/uSWDbei_wxU
Actually, I started this Thursday at 4:30pm. In video I said I started Friday.
Re: Casting: Rear Coil Spring Bumpers
Sunday, September 08, 2019 2:23 PM
Hey all.

The test on the new bumpers is looking fantastic. Nearing the 10,000 mile mark now. Taking the most recent visual look a couple days ago, they show absolutely no signs of deformation. So, I'm now in the process of making a 4 plug mold. I'm taking another trip up to NC in a couple weeks. When I return I'll remove the test samples for a closer inspection. I feel quite confident all will be good. Once that is confirmed, I'll begin to produce them using the same material as the samples.

Does the Amber color matter to anyone? There are two reasons I'd like to avoid using dyes, if possible.
1 is the increase in cost.
More importantly is, from the manufactures web site. "Liquid pigments can often cause a negative effect on a materialís physical properties if too much pigment is added."
Please let me know your thoughts.

I expect to have some ready by mid October.

Re: Casting: Rear Coil Spring Bumpers
Tuesday, September 10, 2019 4:51 PM
Here is a list of all cars that are shown to use these.
Attachments
Rear Spring Bumper Fitment List.jpg (120k)

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