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 148K miles. Hurricane Maria Surviver! ( 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 148K miles. Hurricane Maria Surviver! ( 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 148K miles. Hurricane Maria Surviver! ( 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 148K miles. Hurricane Maria Surviver! ( 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.
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