Epoxy Pump Mod?

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soopirV

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Hi- I ordered the epoxy set (thin 635 with 3:1 hardener, medium set time) from US Composites because it was so much less expensive than West System. So far on my tests it's worked great, so I have no regrets (yet), but I do have one gripe: the pumps are 1:1, meaning the epoxy resin pump puts out 1 fl OZ, and the hardener pump also puts out 1 fl Oz...so, the smallest batch I can make is 4 ounces. That's quite a bit for many of my needs. A solution I've considered is to measure the stroke length of the pump, and restrict it on the hardener, so a full dispense becomes 1/3 of an oz. I thought a piece of CPVC cut to the proper length, and then cut lengthwise to make a "C" shape, which would then fit around the plunger might work. I could then remove it to make larger batches. Obviously I'd have to be pretty precise, but does anyone have any other ideas?

Thanks in advance!
 
I weigh smaller batches. Pumps work great for making tubes. That's about it.
 
soopirV said:
Hi- I ordered the epoxy set (thin 635 with 3:1 hardener, medium set time) from US Composites because it was so much less expensive than West System. So far on my tests it's worked great, so I have no regrets (yet), but I do have one gripe: the pumps are 1:1, meaning the epoxy resin pump puts out 1 fl OZ, and the hardener pump also puts out 1 fl Oz...so, the smallest batch I can make is 4 ounces. That's quite a bit for many of my needs. A solution I've considered is to measure the stroke length of the pump, and restrict it on the hardener, so a full dispense becomes 1/3 of an oz. I thought a piece of CPVC cut to the proper length, and then cut lengthwise to make a "C" shape, which would then fit around the plunger might work. I could then remove it to make larger batches. Obviously I'd have to be pretty precise, but does anyone have any other ideas?

Thanks in advance!
Click to expand...

Use the same stroke-reducing clip on both sides: on the resin dispense 3 reduced strokes, and for the hardener use only 1 reduced stroke. That way you don't have to make the clip any particular size.
 
CarVac said:
Use the same stroke-reducing clip on both sides: on the resin dispense 3 reduced strokes, and for the hardener use only 1 reduced stroke. That way you don't have to make the clip any particular size.
Click to expand...

I like the cut of your jib! Hadn't thought of taking some risk out by just making two identical spacers...going to give that a try!
 
soopirV said:
I like the cut of your jib! Hadn't thought of taking some risk out by just making two identical spacers...going to give that a try!
Click to expand...

I think what the OP is saying is to use one spacer and move it back and forth between pumps. That way even if it's not perfect it's at least the exact SAME for both components.
 
cvanc said:
I think what the OP is saying is to use one spacer and move it back and forth between pumps. That way even if it's not perfect it's at least the exact SAME for both components.
Click to expand...

LOL, even simpler!
 
cvanc said:
I think what the OP is saying is to use one spacer and move it back and forth between pumps. That way even if it's not perfect it's at least the exact SAME for both components.
Click to expand...

In all likelihood, the pumps won't be completely perfectly identical anyway, so you might as well make a pair of spacers and figure out the combination that comes out to the most equal volumes, and leave them on there.
 
CarVac said:
In all likelihood, the pumps won't be completely perfectly identical anyway, so you might as well make a pair of spacers and figure out the combination that comes out to the most equal volumes, and leave them on there.
Click to expand...

If you want the exact values, you might as well use a scale. The scale to get the most accurate results may be a few hundred if not thousands of dollars.

Otherwise you can get really close to the exact values and modify the pumps or buy a scale for $20.
 
Last edited by a moderator:
Last edited by a moderator:
So I tested the pump spacer this weekend, and it worked just fine. Cvanc and CarVac- I opted to cut one spacer, and used it on both pumps. Gave me ~1oz of epoxy, which was perfect for a couple of airframe repairs I had on deck.
 
Neat idea, though I stopped using pumps and instead measure into graduated containers. I use WS, and reasonably careful measuring seems to put me well within the mix ratio range listed in the WS specs, if the cured end result is any indicator.
 

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