Vacuum chamber and plastic for lid?

[Kram]

@Kram was talking to me about maybe putting a shoulder on the bottom "plate" so no welding required, just a seal. Would it need epoxy or some other sealant?

If Im turning both parts I may aswell do it as a shrink fit. Even a sliding fit should hold vacuum with a smear of oil around it.

I need to tidy shed again lots of stuff infront of lathe.

 

[DAPPH]

If Im turning both parts I may aswell do it as a shrink fit. Even a sliding fit should hold vacuum with a smear of oil around it.

I need to tidy shed again lots of stuff infront of lathe.

I seem to recall that we had thick brown grease on the schools vacuum chamber table /base and the glass bell jar a ground glass / faced rim .

 

[Pete.]

What pumps are you all using? Vacuum pumps seem to be rather expensive.

 

[Onoff]

What pumps are you all using? Vacuum pumps seem to be rather expensive.

There's a guy on YouTube repurposed a 12V tyre compressor into one...

Think I read about issues of this sort of conversion getting hot?

Would adding a reservoir help?

 

[daedalusminos]

What pumps are you all using? Vacuum pumps seem to be rather expensive.

I use a BacoEng double stage 4.2CFM (ish) approx £160 Amazon.

It looks similar as a lot of the ones on ebay/Amazon so probably generic far east import.

Edit: 4.2CFM, £160

 

[Kram]

@Onoff The 12v tyre pumps run hot. It will last seconds with glue before it melts.

For now Im using a hand brake bleeder... Not ideal but it will pull 29 inchesHg in a few seconds on a small container.

@Pete. This Vevor seems the best value,

VEVOR 3CFM 1/3HP Refrigerant Rotary Vane Vacuum Pump A/C Vacuum Evacuation Pump UK | VEVOR UK

Discover 3CFM 1/3HP Refrigerant Rotary Vane Vacuum Pump A/C Vacuum Evacuation Pump UK, High-quality Vacuum Pump and Oil No-Flow Back Design at lowest price, 2days delivery, 30days returns.

m.vevor.co.uk

 

[Onoff]

What about an old fridge compressor?

 

[RichardM]

We used Dow Corning high vacuum grease for sealing the flanges in the labs at work.

 

[DAPPH]

We used Dow Corning high vacuum grease for sealing the flanges in the labs at work.

Ah so that's what it was called , 62 years is a long time to remember such trivialities

 

[Kram]

What about an old fridge compressor?

Should work as would a car ac pump I think.

I know vac grease has no volatile componemts but unsure if its safe with acrylic.

Spoke with plastic shop tech guy, he said polycarb wouldnt be good as it creeps more over time, and 20mm acrylic should be ideal. Picked up this 250mm² 20mm thick lump. I will cut the excess off and turn down to 210mm dia.

Did some calculating.. the force on the lid willl be 137kg at 130mm ID, and 335kg for 8"

 

[Onoff]

Should work as would a car ac pump I think.

I know vac grease has no volatile componemts but unsure if its safe with acrylic.

Spoke with plastic shop tech guy, he said polycarb wouldnt be good as it creeps more over time, and 20mm acrylic should be ideal. Picked up this 250mm² 20mm thick lump. I will cut the excess off and turn down to 210mm dia.
View attachment 348143

Did some calculating.. the force on the lid willl be 137kg at 130mm ID, and 335kg for 8"

Is it worth leaving at 250mm2? You can then use on the 197.3mm dia bit when I give you it.

 

[Kram]

Thats why Im going with 210mm instead of 150mm
335kg force at 8" dia does scare me a bit...not that It will get near perfect vacuum its still a lot!

 

[Pete.]

Think of it as 3.3kn, it's not nearly as scary then

 

[Onoff]

Think of it as 3.3kn, it's not nearly as scary then

Or 3 of me...

 

[knighty]

if you're after a bigger vacuum pump I've got a fridge one you can have... not sure on the spec of it, it's mounted to the front of a refrigerated truck body, it looks about 2hp

it's be 3 phase... so you'd need some kind of converter


the problem with using fridge compressors as air compressors is the oil from the compressor works it's way into the air steam so the compressor empties over time.... using one as a vac pump there be so little air flow the oil will last for ages... you can just checking it now and again. I can't get around it to see but most fridge compressors this size have an oil level sight glass

 

[Kram]

Thanks but looks too big for my use, my tiny shed is overflowing again.

I'll try to clear access to lathe and make some progress on this tomorrow.

 

[Kram]

Plan to have this complete and tested tomorrow eve. Just 1" of the other end to bore out and face.

Started with carbide bar, wanted to do a comparison but CBA to swap setup around. The LH bar won, just for ease of seeing the cut.

Should have setup power feed, but its good enough for this.

 

[Onoff]

I'm lost...

You've bored the inside out along its length? Was it just so it looks clean and shiny?

The boring out the other end, that's for a plug/base plate to go in? Delrin / removable?

Then the thick clear sheet will sit on top?

All will be revealed I'm sure in due course!

 

[Kram]

Was it just so it looks clean and shiny?

Yes I was going to do the ends but, as it was extremely rough theres no harm in doing the full bore. Turned nice once I was through the intermittent cut, good excuse to use the big bars.
The delrin plug, was going to do that first until I discovered it wont fit in this chuck.. need to swap the big one.

 

[Pete.]

Did you have a bit of plastic for the lid Mark? I still have some heavy perspex here if you need it.