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Numatx squeezer set up

Jskyking

Well Known Member
Today, I set up my squeezer. It?s not squeezing-4 or -3 rivets to the proper compression length.
- I bled the system three times to ensure no air was in the lines, disconnecting the clear plastic (A,B, and P) at the ports. I set the c-squeezer in a vise to ensure the bleed port was at the highest point of the system.
- I kept the black hyd hose nearly flat to prevent sag and possible trapped air
- checked all the fittings,
- adjusted the air pressure to 74 psi (-4?s) and 44 psi for the -3?s
- topped off the intensifier at the bleeder
- Teflon taped the set screw in the c-squeezer bleeder
- using dextrin 111
The squeezer closes and slightly squeezes the rivets but nowhere near compression specs. I don?t have any air leaks.
Hoping that someone else has had a similar problem and can shed light on this issue.
Thanks
Jt
 
so you don't adjust the piston? Maybe new ones are different. Mine runs at 95 psi. I adjust the length of the piston travel. It screws in and out. Yours just works on pressure?

For dimpling, I make sure that I see the yoke or c-frame flex when setting the dimples.
 
Isolated the problem- Harbor Freight junk regulator. Numatx squeezes like a champ after taking the regulator out of the system and going with Speedaire regulated shop air.
 
Interesting. My Numatx is from 2013, so it works off adjusting the ram length. With that said, I am not actually sure that it would not work the same way. I just keep mine adjusted to 95 psi and adjust the ram length. Maybe it would work the same way as yours. I will try sometime when I am out in the shop.

If I had that the new squeezer, then I would have two regulator permanently setup at the two pressures.
 
Numatx squeezers produce constant force

Jared is correct. There is no cam mechanism (lever principle) in the Numatx squeezer, it works simply off hydraulic pressure. Doubling the air pressure into the intensifier doubles the hydraulic pressure, thus the force. Force = Pressure x area (piston area). I can teach someone to squeeze a rivet correctly when they do not know the air pressure to achieve the correctly formed head, simply by "sneaking up" on the rivet with a very low pressure. Start at 20 psi, then 25 psi, then 30... Very quickly the correct "pressure" (regardless of how accurate the user's gauge is) can be determined, using the .5-.6D height rule for rivets per FAA AC43.13. If it sounds complicated it is not. It is simply quick trials to find what works.

Ken is also correct about the threaded compression pin he has. His unit was an earlier version that I designed that did have a threaded compression pin for coarse adjustment. The problem was that some users were unthreading the pin too far, and did not have enough threads in engagement to carry the 3,000 pounds of force during squeezing, and would damage the threads. So, I simplified the design and removed the threaded compression pin.

Since the Numatx unit has constant force (force along any part of the .55" stroke is the same), it works a little differently than a traditional pneumatic only unit and is not really needed. As others have said, a -4,-6 or -8 rivet of the same material and diameter can be squeezed without any length (die) adjustment. This is a further advantage of the Numatx unit besides being smaller and lighter.

You can also set rivets by adjusting the length of the compression pin with shims, die lengths and so forth, the same as traditional squeezers. But why bother, when you can simply dial up or down the pressure regulator.

Ken also makes a good point: Get two air regulators, and use a two way isolation valve prior to a Y of the two valves (McMaster-Carr or other source). Then you can simply flick an air valve to go with whatever two pressures work for you and 3/32 and 1/8 rivets.
 
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Do you have any insight on the 60 PSI minimum limitation listed in the manual (or am I misreading something)?
 
Numatx can be operated below 60 psi

Yes, you didn't misread the 60 psi limitation, it is a mistake in the manual. Numatx units can be readily operated below 60 psi, and of course need to be operated at about 45 psi to squeeze the abundance of 3/32" AD rivets in RV kits. Hy-Tech Engineering put 60 psi in the manual, despite my objections, as HT has had some customers with commercial units trying to use too low of a pressure (~10-20 psi) to develop lower force. In these cases the units operated very slowly. But for the 3K systems people are using for light aircraft construction, 35 psi is about the lowest pressure needed to squeeze a 3/32" rivet, and the operating speed is just fine.
 
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Mark did the originals. I have one---well the guys at the airport are 'borrowing' it. Worked flawlessly for me, and I'm NOT a structures guy! WE did make a coulple of special dies for colse tollerances like ribs and angles.

Perhaps the new versions are different. Dont know. Mark can tell us---
Tom
 
I am about to return mine. The travel distance of the pin is very small. About 1/4?. I called the company and they said send it back and implied that they have seen this problem before. Does anyone know anything about this issue?
 
Up and running

I'm just starting on my empenage kit and opted to purchase the Numatx system over the standard pneumatic squeeze. Tool performance was very anemic following my first attempt at infusing and bleeding the Dexron III fluid into the simple hydraulic circuit. A second repeated infusion did the trick.
I get acceptable shop heads at 72 psi for -4 (1/8") rivets and 43 psi for -3 (3/32") rivets. I'm sure the readings on my pneumatic gauge will very a bit from any other.
Is there an optimum pressure to use for dimpling? My operating manual is blank on this. Should maximum pressure be used for all dimpling regardless of stock thickness?
 
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I'm just starting on my empenage kit and opted to purchase the Numatx system over the standard pneumatic squeeze. Tool performance was very anemic following my first attempt at infusing and bleeding the Dexron III fluid into the simple hydraulic circuit. A second repeated infusion did the trick.
I get acceptable shop heads at 72 psi for -4 (1/8") rivets and 43 psi for -3 (3/32") rivets. I'm sure the readings on my pneumatic gauge will very a bit from any other.
Is there an optimum pressure to use for dimpling? My operating manual is blank on this. Should maximum pressure be used for all dimpling regardless of stock thickness?

Never got a response to my questions regarding recommended pneumatic pressure during dimpling so I inquired with the Numatx tool developer via a PM. Here is his reply:

Hi Bruce,

I guess the short answer is run the pressure up to as high as you would for riveting. This assumes you are dimpling with the squeezer and a yoke mounted in it (I think this is what you are meaning), as opposed to the squeezer mounted on the end of a C-frame (DRDT-2), which could caused too much stress in the c-frame.

The simple fact is you can not over squeeze the sheet stock, the hydraulic pressure would have to be astronomical to do so. If you doubt this, but a set of flat dies in the squeezer, and squeeze a pc of sheet stock. It wont do anything to the sheet after you release the pressure.

I personally think people get to fussy about the dimple quality, but to each their own. I taught sheet metal to A&P students, and didn't fuss over dimpling to the degree some do. Don't take my comments as a knock on you asking the question, I don't mean it that way.

I hope this helps.

Mark
__________________
Mark Swinford
Aeronautical Engineer
RV-7 N65NX
 
For dimpling I've just always ran around 90psi...or if I'm still setup for 1/8" rivets I just leave it at 86. As his reply suggests it makes little difference.
I'm not sure what the minimum pressure would be, although I'll have to test that out now.

Jared
 
Washer shims

Can I ask which length squeezer set people are using? I?m finding for 3-3.5 rivets I need 60psi with a long (or tall) set and then some additional washers as shims to get enough pressure on the rivet. This is with the long piston installed. I tried squeezing some AN470AD4-5 rivets for the first time today and it took over 100psi and a couple small washers stacked and I still didn?t have the shop head squeezed enough. It sounds like I?m clearly not developing the hydraulic pressure I should. I bled the system several times on initial setup. I used Pennzoil automatic transmission fluid. Could that be the issue?
 
Washer shims

Can I ask which length squeezer set people are using? I’m finding for 3-3.5 rivets I need 60psi with a long (or tall) set and then some additional washers as shims to get enough pressure on the rivet. This is with the long piston installed. I tried squeezing some AN470AD4-5 rivets for the first time today and it took over 100psi and a couple small washers stacked and I still didn’t have the shop head squeezed enough. It sounds like I’m clearly not developing the hydraulic pressure I should. I bled the system several times on initial setup. I used Pennzoil automatic transmission fluid. Could that be the issue?
https://team14le.wordpress.com/2020/02/21/numatx-squeezer/
 
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Can I ask which length squeezer set people are using? I’m finding for 3-3.5 rivets I need 60psi with a long (or tall) set and then some additional washers as shims to get enough pressure on the rivet. This is with the long piston installed. I tried squeezing some AN470AD4-5 rivets for the first time today and it took over 100psi and a couple small washers stacked and I still didn’t have the shop head squeezed enough. It sounds like I’m clearly not developing the hydraulic pressure I should. I bled the system several times on initial setup. I used Pennzoil automatic transmission fluid. Could that be the issue?
https://team14le.wordpress.com/2020/02/21/numatx-squeezer/

I experienced similar results when I first set up my tool some six months ago. I had to repeat the bleed process several times to completely remove any air voids in the system. Once I had all the voids removed the tool works as advertised.
For my setup and regulator 43 psi is all that is needed for -3 rivets, and 75 psi works well for the -4 rivet. It has been pretty consistent.
The brand of transmission oil shouldn't make any difference. There just can't be any air in the line at all.
 
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