Strut Spacer material question...

[subydrift]

Hey guys, I just got myself another 97' Outback and am wanting to build some lift spacers for it. I have them all designed in AutoCAD and Solidworks and have templates made from MDF so I know they'll fit but I am just wondering about materials. I want it to be a 1" thick piece of plastic-like material so I can cut it out rough with a jig saw and then clean it up with the template and a table router. Origianlly I was going to use HDPE as it is used in rally cars and is the same material used by other manufacturers for their spacers. But, my work has an abundance of 1" thick clear acrylic sheets that are going to be discarded soon and I was wondering what you guys thought about using this material for the spacers? I am going to try and get the material specs from our local distributor also. Just hoping someone has had experience with this material in high compression applications that can chime in. I'm mostly worried about it cracking either from being under stress or from the cold weather.

Thanks for any insight/tips/advice, etc.

I found this website that has all of the properties of the 2 materials but no compression strength for Acrylic...

http://www.machinist-materials.com/comparison_table_for_plastics.htm


Robbie

[Subieski]

I would think that acrylic would be too brittle. But i'm interested to see what would work because i have been considering this as well.

[subydrift]

That's what other people are saying too. I'm just curious because its free material for a **** load of it too. HDPE locally will run me about 45 bucks for 2 square feet. Even though it is the preferred material (aside from aluminum but I don't have a mill). Just was hoping I could use the free material. But I'm gonna do a DIY write up on them when I get the right material squared away.

[Rally OBXT]

Hockey puck.

[Daveo]

I would think that acrylic would be too brittle. But i'm interested to see what would work because i have been considering this as well.

This is exactly what I was thinking, brittleness would lead to cracks and your spacers coming apart.

[KevinWelker]

Acrylic is definitely a bad material choice. But it could likely be used for some other cool stuff instead of just being tossed into the dumpster.

[MadMax11]

Just buy some UHMW plastic, basically a stronger version of HDPE. It should be pretty cheap. I got a 1.5"x12"x12" block for $40.
Right now I'm running 0.5" rear spacers, and they're holding up with no issues.

[subydrift]

I thought UHMW was softer than HDPE? Wouldn't it be more prone to compressing under large amounts of weight?

[Daveo]

I thought UHMW was softer than HDPE? Wouldn't it be more prone to compressing under large amounts of weight?

The other way around...

[subydrift]

Ya I found the specs on www.indplastic.com (http://www.indplastic.com). Looks like I'm gonna order a piece of 1" x 12" x 18" UHMW from a local company once the Christmas shopping funds recover. Maybe I'll grab a sheet of the Acrylic and try to use it for something else. Lol...

[grayhamwiebe]

I also thought HDPE was better than UHMW (and I cut the stuff all the time, I'll have to ask my boss about that), if you could get Delrin that is some good stuff, way too expensive though. Why aren't you just using some cheap aluminum (5052)?

p.s. could i get those plans off of you somehow, going to make some out of 3/4 aluminum but it's winter and i only want to unbolt my struts once. -30C (that's Celsius which is about -20F) and car modding don't make things easy.

[subydrift]

Grayham, I thought I emailed you those templates already? I know I did but it must not have gone through. I'll resend them.

[impoutback 97]

Try some DELRIN. you can find it at machine shops. Or a chunk of aluminum would be nice and lite weight.

[MadMax11]

I also thought HDPE was better than UHMW...

"While HDPE seems to be much like UHMW they are two totally different animals. HDPE is much too soft and easily damaged to be used for precision work. As a test, take a piece of UHMW and a kitchen knife and try to slice into one of the side corners. See how thick of a sliver you can remove. Then use the same amount of force to try to remove a sliver from HDPE.

I have used HDPE in those instances where I couldn't get UMHW in the time frame it was needed. However, I changed it to UMHW as soon as I was able."

Or if you want the wikipedia technical version:

"In general, HDPE molecules have between 700 and 1,800 monomer units per molecule, whereas UHMWPE molecules tend to have 100,000 to 250,000 monomers each."


Basically, UHMW is more dense than HDPE, so it can withstand greater everything.

[subydrift]

I ended picking up 3 pieces of 1" x 12" x 13" HDPE from a local company. It was a third of the price of the UHMW and I figure if its good enough for the saggy butt shims then it will be fine for these. I'm gonna cut out 3 sets and see how they go.

[whitefcdrifter]

I know this is kinda old bit how'd they turn out? Im cutting my out of one inch 6061 aluminum on my waterjet and rear shims must likely out of .250 aluminum

[sifu]

Any updates? Looking to do this myself with 97 obs...anyone know where I can find the templates to give to my machinist?

[subydrift]

I've had a set of 1.25" HDPE spacers on my outback now since April and everything is great! No problems with compression, cracking, etc. I have some pics of the install and some templates so I'll get those posted when I get off work!