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| Author: | Ruby50 [ Sat Jan 19, 2019 10:24 pm ] |
| Post subject: | Cheap vacuum bag |
Anybody work with this before? https://roarockit.com/woodworking-tutorials-categories It is a hand powered vacuum system designed for making laminated skateboards. The pump is the same one used for sucking the air out of a wine bottle, and the fitting looks like an adaptation of the one that fits in the bottle. Ed |
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| Author: | J De Rocher [ Sat Jan 19, 2019 11:21 pm ] |
| Post subject: | Re: Cheap vacuum bag |
I don't see any details on the website to go with that photo. My question would be how much vacuum can you pull with that set up. I do vacuum clamping for gluing braces and the pump I use can pull 24" Hg. |
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| Author: | meddlingfool [ Sun Jan 20, 2019 1:07 am ] |
| Post subject: | Re: Cheap vacuum bag |
What does 24" Hg represent? |
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| Author: | J De Rocher [ Sun Jan 20, 2019 1:22 am ] |
| Post subject: | Re: Cheap vacuum bag |
meddlingfool wrote: What does 24" Hg represent? Twenty four inches of mercury is equivalent to 0.8 atmosphere and converts to a pressure of 11.8 lbs/square inch or 81 kPascals. For an x-brace on one of my dreadnoughts, that would mean a total pressure of about 78 lbs spread out evenly over the length of the brace during vacuum clamping. |
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| Author: | ballbanjos [ Sun Jan 20, 2019 5:15 am ] |
| Post subject: | Re: Cheap vacuum bag |
I used one for awhile, and it worked. It was a bit slow in pulling a vacuum (required lots of elbow grease), but it pulled enough to work. How many inches of mercury, I have no idea since I had no vacuum gauge at the time. The bag itself is decent quality. I've since gone to one of the Joe Woodworker designed vacuum pump rigs, and it is a lot quicker, but I can't say that I can really tell any difference in the resulting laminations. I still use the bag that I got with the skateboard rig. Dave |
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| Author: | Mark Mc [ Sun Jan 20, 2019 2:14 pm ] |
| Post subject: | Re: Cheap vacuum bag |
I also used that hand pump with the LMI vacuum bridge clamping jig. You can adapt the valve off one of the bags and fit it to the bridge clamping frame. It works quite well and allows you to do vacuum clamping of bridges without needing a costly vacuum pump setup. |
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| Author: | dpetrzelka [ Mon Jan 21, 2019 12:44 pm ] |
| Post subject: | Re: Cheap vacuum bag |
Dave and Mark, Is it pretty straightforward to adapt a Roarockit vacuum bag to a 1/4" or 1/8" fitting for use with a traditional electric vacuum pump? Thinking it would be nice to try one for laminated sides I have planned. |
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| Author: | ballbanjos [ Tue Jan 22, 2019 6:45 am ] |
| Post subject: | Re: Cheap vacuum bag |
It was pretty straightforward--I just pulled out the wine vac fitting and replaced it with one of these: https://www.veneersupplies.com/products/Bag-Stem-Assembly.html It fit in the same hole. Dave |
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| Author: | Mark Mc [ Tue Jan 22, 2019 3:26 pm ] |
| Post subject: | Re: Cheap vacuum bag |
Daniel Here is a Robbie O'Brien video on using this system to do laminated sides: https://www.youtube.com/watch?v=n_iKG9hyggk This is what the bag outlet looks like when you pull the grey pump nipple-valve off. It has about half-inch external diameter and quarter inch internal. I am sure you can fashion a connection to your vacuum pump. In the photo I have fitted the nipple-valve to the LMI bridge clamp jig so I can hand pump a vacuum in that. Attachment: vacuum bag.jpg
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