Star roller vs press

[pyroguy1960]

Will I need any equipment aside from pumps, star plates and tooling? Gauges?

 

I also bought a pressure gauge from wolter, the 10k psi one. I find that extremely helpful when pressing as it allows me to keep a consistent pressure on the fuel grain no matter I'm pressing. I initially had problems with my stars all burning out at the same time because they weren't all pressed with the same amount of pressure. The gauge will be even more neccessary if you're going to pressing rockets & it doesn't hurt when pressing gerbs either, keeps the burn very consistent especially if you're using them for drivers.

 

Another thing to keep in mind is you may need extraction sleeves if you plan on pressing large comets, I've found it impossible to extract large comets intact without them, especially if they contain any Ti.

 

My two cents on making your own press is it wouldn't be worth it at all given how cheap the harbor freight ones are. You'd only save probably around 70 bucks and it would be a labor intensive build and the results probably wouldn't be nearly as good as a commercial press in terms of smooth functionality.

[TheArchitect23]

 

My two cents on making your own press is it wouldn't be worth it at all given how cheap the harbor freight ones are.

 

well, my 2 cents:

just purchased a harbor freight 12 ton press 3 days ago.

it is going back. darn thing damn near broke my rocket tooling.

after about 2,000 psi it drops off to one side, or the other. tried shims, then it would do it front to back.

The floating jack and floating base are not a good combo. to top it off the legs are welded crooked, the whole thing rocks from side to side.

 

You get what you pay for....

[pyroguy1960]

That is correct the harbor freight cheapo press is useless for doing rockets because it's so sloppy, I have since gotten rid of mine and purchased a 20 ton arcan, it's really nice.

[Scott2Fisher]

how does the forum feel about using say a 2x4, or similar, with wood dowels or metal rods that fit into holes drilled into a second 2x4 as a homemade star plate? i know i cant be the first to think of this, but i haven't seen mention of it elsewhere on the site

[Mumbles]

I think you'd probably have trouble trying to get the wood smooth enough to release the comets you'd be making. If you lined the holes with a metal or PVC pipe or something, I don't see why it wouldn't work. I made a gang pump out of PVC before. It worked alright, but I did find I had trouble getting enough compression from just hammering the composition. I had gotten a larger hammer to solve this, but never got a chance to try it out.

[pyroguy1960]

I would think this would be problematic for a few reasons. The main one being that wood is so affected by it's environment and given that you have to wet the comps, I just don't think you'd be able to keep the tolerances where they need to be with the wood always swelling and contracting. Another being that wood is very porous, so you'd probably have comp sinking into it and gumming up the works. A final concern I would have is the wood splitting and marring when you hammer it and if you put it in a press, forget it, it would probably split I reckon.

If I was going to try it I would skip the 2x4 and make it out of a nice hardwood, then urethane it, then wet sand it with extremely fine sandpaper.

I think a better approach would be buying sheet plexiglass, I think they make that stuff fairy thick and in rods and I'm pretty sure it's cheap too. But if I took this approach I would definately research how to drill it correctly otherwise you might end up with rough holes or melting/cracking issues.

[AirCowPeacock]

I tried cutting plexiglass for a totally unrelated project; the cut didn't need to be all that clean, but I repeatedly found the material melting itself back together after the blade passed by, unless I went extra slow and did it by hand. Edited January 14, 2013 by AirCowPeacock

[WonderBoy]

ACP,

What saw were you using to cut the acrylic? I cut acrylic on a table saw almost every day at work, and do not experience these problems. I set the blade higher than normal so the teeth are traveling in more of a downward motion to cut vs setting the blade to a normal height and melting through the plex. There will be chip out, but this can be quickly smoothed by running the edge through a Jointer.

 

S2F,

Personally I would stay away from acrylic just because it is a pain to work with. I second Mumbles' suggestion of a PVC gang pump. It is easy and cheap to make, and can be used with or without a press.

 

 

WB

[AirCowPeacock]

A scroll saw totally fused the two peices back together, but I used a keyhole saw after I figured out that didn't work. If I went really fast with the keyhole say the peices partially fused back together, and had to be forced apart. I needed to cut a circle.

[dagabu]

I picked a saw blade that had a wide cross section at the teeth but a narrow spine, set to the max height and a generous spray down with silicone spray, I got a clean cut on my shield material for the press.

 

-dag

[nater]

I just used a table saw to cut some lexan down to size for a shield. I didn't have any problems.

[WonderBoy]

Polycarbonate (Lexan) is a completely different animal than acrylic (Plexiglass). Has anyone made a star plate out of polycarbonate?

 

 

WB

[pyroguy1960]

Dagabu, correct me if I'm wrong but didn't kyle have a DYI on passfire about this? I lost my creds and haven't gotten around to emailing him....wasn't sure if he made it out of polycarbonate or acrylic.....

[WonderBoy]

The article on Passfire uses a polyethelene cutting board and Al pins. I have made one; I could never get it to work as well as I'd hoped it would. My pin plate would always bind up in the female plate and had to be pried apart.

 

 

WB

[pyroguy1960]

Yea making a starplate that works well is not a simple task, gottta get the tolerances just right.......I leave it to the pros at wolter.