MakerGear Forum

I recently built a vacuum pump using some propane tanks as the reservoir and a rebuilt Thompson motor I bought online. The motor has cooling fans on each end which had no blade guards, so I printed some to match my color scheme. As a 3D printed object this is not that impressive, but it certainly solved a problem in a quick and professional looking way. The vacuum pump itself turned out great. I'll be using this to vacuum bag carbon fiber parts to use on the RC blimp project. The blimp itself uses quite a few printed components.

Nice job Pyro. Looks like it came that way and great choice of color!

Spotopolis wrote:Nice job Pyro. Looks like it came that way and great choice of color!

Thanks. Black and orange is my favorite color scheme, so I have lots of black and orange filament

Is that a repurposed propane cylinder as an expansion/buffer tank?

insta wrote:Is that a repurposed propane cylinder as an expansion/buffer tank?

Yep. There's actually two propane tanks there... one is the larger gas grill type at the bottom which is the main vacuum reservoir, then there is a smaller camping propane tank (the green ones) at the top which is used to drain the vacuum off the pump intake when it shuts off. If the vacuum is not removed from the intake then the motor is unable to start up again once it shuts off due to the suction pulling on the piston.

The camping tank has been modified with a bleeder valve where the over-pressure release valve used to be. This is not necessary for using it on a vacuum pump, but it is necessary if you want to refill your own camping tanks with propane rather than discarding them when they are done. You have to open that valve when filling them. If you try and use pliers to pull the pin on the release valves that are normally installed, the freezing temps from propane flashing on it's way out will damage the rubber seal and they will leak after that. I use a rubber ball that is rated to -20F as the stopper (McMaster part 1241T1), then a thumb screw to hold it in place (McMaster 98704A545). Even though propane flashes at -40F, the ball still seems to hold up. Of course with the pressure release valve removed, it is up to you to not overfill it or expose it to heat. The DOT makes it illegal to transport the tanks on public roads once you do this, but I was burning through so much propane on my hot air blimp project that the money saved on doing my own fills was substantial.

nice job on that!

jimc wrote:nice job on that!

Thanks. After watching that guy you linked to make the lost PLA molds for your safe project I thought maybe I could also use this pump to pull the air bubbles out of plaster if I ever get into doing that kind of work myself.

I found this video on how to make a low cost DIY foundry for melting metal without using propane. You wouldn't think charcoal would be capable of producing this kind of heat! https://www.youtube.com/watch?v=lSoWxG3 ... e=youtu.be

will your pump pull a perfect vacuum? degassing requires a very strong vacuum. i have 2 vacuum pumps here. one of the oilless gast style and the other is for hvac. the gast style would work for things like vacuum bagging but never pull the kind of vacuum to degas semi thick liquids like plaster or resins. i had to buy the hvac pump for that one.

The vacuum switch goes up to 28" Hg, but I haven't had the pump up to the max yet. It gets to 21" pretty easily though. I'll have to see if it will go all the way to 28", which would only be 2" short of a perfect vacuum.

pyronaught wrote:

jimc wrote:nice job on that!

Thanks. After watching that guy you linked to make the lost PLA molds for your safe project I thought maybe I could also use this pump to pull the air bubbles out of plaster if I ever get into doing that kind of work myself.

I found this video on how to make a low cost DIY foundry for melting metal without using propane. You wouldn't think charcoal would be capable of producing this kind of heat! https://www.youtube.com/watch?v=lSoWxG3 ... e=youtu.be

I built one of those, it turns aluminum into puddles really quickly. Lost-PLA castings work out alright.