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Riveting Air Pressure - I Wish I Had Known

skelrad

Well Known Member
Friend
This may be common knowledge, but a lesson learned for me that will hopefully help someone else who is just getting started:

As part of my original tool kit, I got an inline air flow restrictor to put on my rivet gun (a basic brass valve, not a pressure gauge). Theoretically, you can use this to dial in the proper airflow at the gun itself, allowing you to set the main line at one pressure and leave it there. Because all other tools tend to use 90 psi, that's what I set my main line at. I would then restrict the air at the gun using the valve. This definitely worked, in that the power of the gun was impacted, but for the longest time I really struggled with control while riveting. Especially with 4- rivets, at the position I'd have to open the valve to for enough power, the gun would dance all over the place. It got to the point where I was extremely frustrated and dreaded riveting.

Fast forward, and someone (I wish I could remember who) suggested ditching the inline restrictor and just setting pressure at the wall. I couldn't wrap my head around why this would make a difference, but I gave it a shot. Man oh man, what a difference! I'm sure one of you know the reason, but I don't really care at this point! :) If I take the inline valve out of the picture, the way the gun hits is completely different. Now I actually look forward to riveting sessions, because I know I have at least a decent chance of success! Today I was in a bit of a lull, so I went back to my AN470's on my horizontal stabilizers and rear spars of my wings. More are gouged and dinged up than I care to admit, all because I couldn't control my gun. I drilled out around a dozen rivets and reset them, all turning out beautifully. This is definitely in part to me now having more rivet sets in my arsenal that fit situations better, but it's also due to being able to control the gun better.

Maybe it's just in my head, but for any newbie out there, if you are really struggling with rivet gun control and are using the inline valve at the gun, just give it a shot and use your main line pressure instead. It takes a bit more time to change the pressure at the wall, but I find it soooo worth it. The pressure I use depends a bit on the situation, but I tend to use about 30 psi for 3- rivets and 40 psi for 4- rivets (mostly because it's easy to remember - I've used a lot of variation with success).

Could be complete placebo. I don't care. I'm a much better riveter now.
 
Another thing I'd throw in here is that trigger control is very important. I personally prefer to keep the pressure to my gun cranked up pretty high, and when I shoot, I put my middle finger behind the trigger. This gives me pretty good control, and works out well for me.

However, when my partner was helping me rivet the fuselage canoe many moons ago, things were not going well. It took a while to figure out that her small hands weren't capable of doing my two-finger trigger approach. In that case, carefully controlling the pressure at the gun became very important - for both getting lots of good rivets and maintaining relationship harmony.

:)
 
Just me

I run the pressure at like 35 psi for size 3 and 45 for size 4. I use the valve to help control the gun. The air pressure seems to set the inital strike, and the needle valve on the gun goes into play on the subsequent strikes. I tweak the valve depending on rivet length and difficulty setting. JMHO YMMV
 
I run the pressure at like 35 psi for size 3 and 45 for size 4. I use the valve to help control the gun. The air pressure seems to set the inital strike, and the needle valve on the gun goes into play on the subsequent strikes. I tweak the valve depending on rivet length and difficulty setting. JMHO YMMV

I’ll have to try the combination and see what it changes. I was so pleasantly surprised by dropping the line pressure that I haven’t played around with the valve any more.
 
Finger behind the trigger..try it.

As Philip mentioned, its amazing the control gained by putting your middle finger(or ring finger, as I do..I pull the trigger with my middle) behind the trigger when shooting. It keeps you from over shooting, especially on the initial squeeze. At my day job, and anyone who has done this professionally, your usually working with shop air pressure that is 90-100 PSI, and not easily regulatable. The knob-on-gun regulators are flow regulators, and initial pull will always be line pressure.
 
Trigger Control

I am under the impression that the force of a single strike is the same for all strikes at a given pressure. Is this not true? We have the feathering trigger, but....

Interesting thread. I hope this is not considered drift....

Mike
 
Something to consider

A regulator and a flow restrictor (variable orifice, valve, etc.) are not the same.

- The valve position only holds pressure for one set of conditions/flow. If line pressure changes or trigger position is inconsistent, the gun will hit inconsistently.

- In a no-flow case, the gun (or any device) is feeling full pressure at first so those first x# hits can be very high if you go full trigger.

Before anyone objects, whatever technique works for someone is fine. Small in-line regs are cheap and remove variables -> make things more consistent/easier.. This is probably the right place to start for most people until they get a feel for their tools and develop their skills. My $.02.
 
Too much pressure

It is my belief that too much line pressure, or too much pressure at the gun creates a difference in the final product.

In Sport Aviation, there was a covered photo of a polished WW2 plane. Around the turtle deck area, every rivet had a slight dimple of the skin. I think this was caused by higher than necessary air pressure on the gun.

When I did my wings, I lowered the air pressure so every rivet took a fair number of hits, but the skin remain undisturbed.

So while rivets can be set with different air pressure, I found the lowest pressure preserves the quality of the skin finish. JMHO
 
Another thing I'd throw in here is that trigger control is very important. I personally prefer to keep the pressure to my gun cranked up pretty high, and when I shoot, I put my middle finger behind the trigger. This gives me pretty good control, and works out well for me.

However, when my partner was helping me rivet the fuselage canoe many moons ago, things were not going well. It took a while to figure out that her small hands weren't capable of doing my two-finger trigger approach. In that case, carefully controlling the pressure at the gun became very important - for both getting lots of good rivets and maintaining relationship harmony.

:)

+1

It is a bit of an art, but mastering trigger control is a better all around solution, as the builder can adjust for every situation without having to worry about going back to the regulator. It takes time to master that skill, but infinitely valuable if you do.

Larry
 
Shop set up

Lots of good tips already. I have a different set up from most.
Main air hose from the compressor carries full pressure.
It has a three way manifold at the end with quick connect fittings.
I use two HF whip hoses at the work area.
https://www.harborfreight.com/1-4-quarter-inch-x-5-ft-swivel-whip-hose-98944.html
The compressor end has a mini regulator. I prefer the RTI. I also have one on my paint gun.
Rti Micro Air Regulator 1/4" https://a.co/d/1DqLkt5
The gun end has a quick connect fitting to swap low pressure tools.
The other whip hose has a HF mini regulator set at 90. No need for precision.
I run 30 for #4 rivets and 23 for #3 rivets. RTI regulator never moves once set. Every hit is exactly the same.
Paint work is similar except the main hose is bigger and the regulator is attached to the gun.
 
There is no disputing that there is a difference between the airflow control needle valve and an actual air pressure regulator, and how they function, but 30+ years of experience using the flow control regulator on rivet guns has shown me that that doesn’t matter.
We have a half dozen rivet guns in our shop and they all have the flow control valve on them, and we have been using them that way for decades.
I am not clear on why the OP or anyone else would have had such a difficult time when using the flow control valve when so many others have had good results. There is a reason that that has been sold for decades as an accessory with rivet guns. This was originally started I believe by Bob Avery.
I have taught many people to rivet through training seminars that we used to hold here at Van‘s, forum presentations at Oshkosh, and just one on one and people shops helping them get started. I have always taught people how to use the flow control valve on a rivet gun. As already mentioned by others this allows leaving the shop line pressure at maximum for use with other tools, and it allows for a very precise fine adjustment of the rivet gun so that riveting performance can be very consistent over hundreds of rivets.
I don’t know for sure what has caused people problems using the flow valve, but my guess is that there is other circumstances involved that are unknown. One might be the use of a small diameter flex hose near the rivet gun. I don’t recommend that because it is a long length flow restriction that can cause issues.
The technique that I have always taught is to set the rivet gun up so that a rivet fully sets in about three seconds after using a normal throttle up on the Traeger and reaching the point that the Traeger is fully depressed. This will give great control of the gun and great consistency from one rivet to another. With just a little bit of practice even an inexperienced helper can get to a point of being very consistent. I would never teach someone to rivet using a high air pressure and having to regulate with their trigger finger, the actual output of the rivet gun for each and every rivet. This even goes against standard practice in factory production environments.
 
There is no disputing that there is a difference between the airflow control needle valve and an actual air pressure regulator, and how they function, but 30+ years of experience using the flow control regulator on rivet guns has shown me that that doesn’t matter.
We have a half dozen rivet guns in our shop and they all have the flow control valve on them, and we have been using them that way for decades.
I am not clear on why the OP or anyone else would have had such a difficult time when using the flow control valve when so many others have had good results. There is a reason that that has been sold for decades as an accessory with rivet guns. This was originally started I believe by Bob Avery.
I have taught many people to rivet through training seminars that we used to hold here at Van‘s, forum presentations at Oshkosh, and just one on one and people shops helping them get started. I have always taught people how to use the flow control valve on a rivet gun. As already mentioned by others this allows leaving the shop line pressure at maximum for use with other tools, and it allows for a very precise fine adjustment of the rivet gun so that riveting performance can be very consistent over hundreds of rivets.
I don’t know for sure what has caused people problems using the flow valve, but my guess is that there is other circumstances involved that are unknown. One might be the use of a small diameter flex hose near the rivet gun. I don’t recommend that because it is a long length flow restriction that can cause issues.
The technique that I have always taught is to set the rivet gun up so that a rivet fully sets in about three seconds after using a normal throttle up on the Traeger and reaching the point that the Traeger is fully depressed. This will give great control of the gun and great consistency from one rivet to another. With just a little bit of practice even an inexperienced helper can get to a point of being very consistent. I would never teach someone to rivet using a high air pressure and having to regulate with their trigger finger, the actual output of the rivet gun for each and every rivet. This even goes against standard practice in factory production environments.

I truly have no idea why there was such a difference from using the restrictor and cutting it out of the picture. It's possible that everything else I've learned over time finally just clicked and my riveting improved because of that, but I literally went from riveting a dozen rivets with the restrictor then 30 seconds later doing it without the restrictor and having much more control. Maybe there is some other compounding variable that I haven't discovered. One thing I did notice with the restrictor is that the values I used didn't always stay consistent, even within a riveting session. So perhaps it's a lemon and not doing its job? I know they're very simple, but I haven't taken it apart to see if everything is as it should be inside.
 
There is no disputing that there is a difference between the airflow control needle valve and an actual air pressure regulator, and how they function, but 30+ years of experience using the flow control regulator on rivet guns has shown me that that doesn’t matter......

Going to defend my advice and disagree with the "application". This guy doesn't have 30 years experience and it's not going well for him yet. Two months from now he'll have probably have developed his touch. Until then, he probably is using an air compressor versus constant psi shop air. His set/reset probably has a 30 psi dead band (or more) to prevent short cycling of the equipment. Small air receiver? The pressure varies even more. Is the flow restrictor a needle valve with fine adjustment or a non-ported ball valve where the smallest change can significantly affect effective area thus downstream pressure.

Everyone here has driven a rivet at full shop air full pressure, used too large a gun, etc. in the name of convenience. I'll state again, remove as many variables as possible early on. This will surely save some time, parts, and money.

@Wirejock. Got a manifold and octopus in my hangar as well. Full pressure and two regulated. Very nice compared to popping QDs and changing pressure all the time; drilling versus squeezing versus driving. It's a very cheap convenience.

@Skelrad. Weigh all of the aforementioned advice and see what makes sense to how you're perceiving things. You'll get there but it won't be without pain. We've all lived through that.
 
90 for all shop tools

Drop through a separate regulator/filter to 40 for HVLP spraying.

The end :D

As someone said - practise with your tender fingering ;)
 
I’m now on my second build. For my first build, I used a 2x gun exclusively. For my second build I’ve added a 3x gun, and am happy I did (mostly for -4 rivets and the offset rivet sets). Early on, I eliminated the flow regulator and always regulate pressure at the compressor. Using trial and error, I have developed a table of pressures for different rivet sizes, different rivet sets, and different guns - range is 25 to 85 psi. For example, a long reach offset rivet set gets a lot more pressure than a short mushroom set. With a specific size of rivet, I pick the rivet set and gun I want, look at the table and set the pressure. I will still tweak values for circumstances, but this gets me really close from the start. YMMV
 
My comment about 30+ years of experience wasn’t to make a point in winning an argument. All I ever want to do is help people learn. I started out with no one to help or show me what to do since I was one of the earlier RV builders in my area, but I did figure it out via trial and error.
There are so many different factors that can be involved and very often important information is left out when people are describing a difficulty. One detail that is important if using the flow valve is to not run the regulator on the air compressor at the highest pressure that you can get. It should be regulated down 20 or so psi from what the max tank pressure is. This provides a little bit of a buffer and allows the compressor to keep the line pressure steady up at the rivet gun.
Another detail that is often missed is some people are using the swivel adapter with a ball valve that usually has a black knob on it. There is no indexing of the knob and a quarter turn goes from full off to full on. This is not the in-line flow valve That I and many others are talking about and it should never be used for controlling a rivet gun. The one I am talking about has a very fine adjustment with each click of the knob. This allows Novits builders a lot of control and helps avoid messing up rivets or even worse damaging the structure, once they have gotten the rivet gun dialed in for the structure they are working on.
That alone is the one big benefit of using this method. Using full pressure and relying on the performance of a trigger finger is a recipe for disaster in my opinion. Especially early on when somebody is learning and they need good rivets right from the start. A secondary point would be that as many often argue in regards to piloting skills no one is perfectly on their game every single day. With a method to have fine control of the output of the rivet gun that no longer matters, because the gun will do the same thing every time as long as everything else is set up correctly i.e. an air compressor adjusted so that it can Maintain a relatively constant line pressure, etc.
 
How do I get repeatability with a flow valve setting? Try it against the wooden block and learn the "feel" of the gun?

If it was just -3 and -4 rivets, it wouldn't be an issue, but same as the others, I found that I use different pressures for different riveting scenarios. More pressure for back-riveting, offset riveting, way more for indirect riveting. Little pressure when forming the bends.
 
Drop through a separate regulator/filter to 40 for HVLP spraying.

When spraying paint, most experienced folks will tell you to ALWAYS run MAX pressure through the hose and regulate at the gun. This is especially true with HVLP that needs a lot of flow. Reducing pressure before the hose will also reduce volume through the hose AND produces greater pressure variances at the gun.

You will not find many paint shops that do not have the regulator mounted to the gun. There is a reason that most any paint gun you buy has a regulator attached to it. I check and reset pressure after EVERY setting change on the gun.

Larry
 
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What others have said pressure and flow are two different things. A valve or restriction will control flow because it it reduces the line size as it flows thru the orifice. What you need for riveting anD paint spraying equipment is a constant air pressure. That is best had from a spring, diaphragm and needle valve assembly called a air pressure regulator. A regulator at the business end especially on a long supply line is the best choice for controlling that final pressure.
 
The technique that I have always taught is to set the rivet gun up so that a rivet fully sets in about three seconds after using a normal throttle up on the Traeger and reaching the point that the Traeger is fully depressed. This will give great control of the gun and great consistency from one rivet to another.

Scott, perhaps you could expand on this a bit. With a needle valve the initial pressure at the trigger will be full line pressure, quickly dropping to some lower pressure across the needle restriction. The key seems to be the "normal throttle up", i.e. offsetting the initial high pressure with progressive trigger displacement over some period of time. Care to describe it in detail?
 
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RTI Mini Regulator

When spraying paint, most experienced folks will tell you to ALWAYS run MAX pressure through the hose and regulate at the gun. This is especially true with HVLP that needs a lot of flow. Reducing pressure before the hose will also reduce volume through the hose AND produces greater pressure variances at the gun.

You will not find many paint shops that do not have the regulator mounted to the gun. There is a reason that most any paint gun you buy has a regulator attached to it. I check and reset pressure after EVERY setting change on the gun.

Larry

That's how mine has been set up since day one.
20220820_082044.jpg
 
Air oil separator

Larry,

I'm assuming that red cylindrical do-jobby below the regulator is a filter of some sort. I've never seen that one - where can you get it?

It's just a cheap, Harbor Fright disposable air/oil filter. I track usage and toss them periodically.
 
Scott, perhaps you could expand on this a bit. With a needle valve the initial pressure at the trigger will be full line pressure, quickly dropping to some lower pressure across the needle restriction. The key seems to be the "normal throttle up", i.e. offsetting the initial high pressure with progressive trigger displacement over some period of time. Care to describe it in detail?

The reason we use aviation rivet guns instead of an inexpensive air chisel, which looks like a very similar tool, is the control that the rivet gun has with the variable throttle trigger.
The best technique when using a rivet gun is to ease the throttle open to what ever amount is desired. Not slam your finger on the trigger and open it as quickly as possible. I am not talking about a long period of time but it is still longer than slamming the trigger fully down.
I mentioned that I teach to set the guns so that a rivet fully sets in about three seconds. Maybe the first one and a half seconds of that time is throttling up the gun while you pull in the trigger. That may not seem very long but it’s a much longer time than if you just pulled the trigger quickly.
I agree that there probably is a pressure drop as you’re initially pulling the trigger but I don’t see that that really matters. What is important for consistency is that what ever happens, happens the same every time. So, if we are adjusting the line pressure at the air compressor and then adjusting the air flow with the needle valve at the gun, to get the result we want, and that result is repeatable rivet after rivet, it doesn’t really matter what the dynamics are of what’s going on as far as line pressure goes. At least not in my mind.

It has already been mentioned that anytime you change anything in the riveting equation, something has to change to compensate for that. Change from conventional riveting to back riveting, or from a short rivet set to a much longer rivet set, or a different rivet length, will change the amount of energy that is required from the rivet gun. That is the number one main reason that using the flow control valve is beneficial. It gives you the ability to instantaneously change the output of the gun as your need for different performance changes.

I mentioned different length rivets being one of the variables… The primary reason for that is because different length rivets are usually associated with different thicknesses of structure. Often times that also equates to how stiff the structure is. The stiffer the structure, the heavier the hit will have to be from the rivet gun to properly get the rivet set in the acceptable amount of time. So, when riveting on a major assembly such as a wing, as you move from lighter substructure such as mid cord on a wing rib and transition to setting rivets along the main spar flange, it will take a harder hit on that heavier spar structure. When I am doing riveting work such as this, I am opening and closing the needle valve a few clicks up or down as needed as the rivet lengths and sub structure changes.

Some people choose to just keep the line pressure turned up quite high and just regulate the gun with their finger as they change from one structure situation to another. My opinion is that it is very hard to be consistent with that method. Especially for a new novice builder. With my method, all the person on the gun has to be able to do is pull the trigger the same way over and over and over, and if the person on the bucking bar is performing well for each rivet, every rivet on similar sub-structure will be very close to the same. When the sub structure changes just dial the control up or down a few clicks as appropriate and shoot a rivet. Check it and see if it’s good and maybe make a slight adjustment one way or the other and then continue riveting. With a little bit of experience I have found that most people get to where they can pretty much guess very close with any adjustment they make and then just continue on.
 
Maybe the first one and a half seconds of that time is throttling up the gun while you pull in the trigger.

Excellent, thanks.

I agree that there probably is a pressure drop as you’re initially pulling the trigger but I don’t see that that really matters.

No question, with the needle valve, pressure at the trigger drops from full line pressure to some unknown lesser pressure during that 1.5 second squeeze. I say "unknown" because apparently you shoot a test rivet or two to find the desired needle valve setting by feel.

So far we have three different methods described, (1) initial full line pressure dropping to a valve-restricted pressure, (2) full line pressure entirely controlled by trigger displacement, and (3), regulated line pressure.

Believe me, I have no issue with methods (1) and (2). However, the skill input is something like learning to play dolce and marcato on the piano. I'll suggest we might have a higher success rate starting new gun operators (in particular the random helper) with (3). It allows the assignment of a specific, repeatable pressure value to a particular rivet or operation, and the only trigger skill required is teaching the operator to make sure the gun has completely stopped before relaxing the push against the work.
 
I mentioned different length rivets being one of the variables… The primary reason for that is because different length rivets are usually associated with different thicknesses of structure. Often times that also equates to how stiff the structure is. The stiffer the structure, the heavier the hit will have to be from the rivet gun to properly get the rivet set in the acceptable amount of time. So, when riveting on a major assembly such as a wing, as you move from lighter substructure such as mid cord on a wing rib and transition to setting rivets along the main spar flange, it will take a harder hit on that heavier spar structure. When I am doing riveting work such as this, I am opening and closing the needle valve a few clicks up or down as needed as the rivet lengths and sub structure changes.

This.... As a new builder, this is something that took me a long time to figure out. I wish someone had told me this early in my build because I would get frustrated trying to set long rivets in stiff sections of the structure. It didn't initially occur to me that I had to turn up the pressure. I took the basic sheet metal class and they did a great job of teaching the basics of riveting but didn't address what to do when you have to set longer or bigger rivets.
 
Needle valve?

...then adjusting the air flow with the needle valve at the gun, to get the result we want, ... I am opening and closing the needle valve a few clicks up or down as needed as the rivet lengths and sub structure changes.

Scott, what kind/brand of valve are you using? I tried a couple different valves and they were all the same. No clicks and go from fully restricted to wide open in less then 10 degrees of rotation.

My current setup has the "regulator" with a pressure gauge between that and the gun so I can tell what my actual driving pressure is. FYI, with this setup I noticed it takes 3-4 stokes to drop from line pressure to restricted pressure
 
Excellent, thanks.



No question, with the needle valve, pressure at the trigger drops from full line pressure to some unknown lesser pressure during that 1.5 second squeeze. I say "unknown" because apparently you shoot a test rivet or two to find the desired needle valve setting by feel.

So far we have three different methods described, (1) initial full line pressure dropping to a valve-restricted pressure, (2) full line pressure entirely controlled by trigger displacement, and (3), regulated line pressure.

Believe me, I have no issue with methods (1) and (2). However, the skill input is something like learning to play dolce and marcato on the piano. I'll suggest we might have a higher success rate starting new gun operators (in particular the random helper) with (3). It allows the assignment of a specific, repeatable pressure value to a particular rivet or operation, and the only trigger skill required is teaching the operator to make sure the gun has completely stopped before relaxing the push against the work.

I have used all three methods throughout the years and with that I still feel that method 1 is the best.
In practice, I don’t see that it is any different then method three as far as the results that are achieved though my opinion is that it actually gives you finer adjustment and more control over what’s happening.
I don’t think it’s true to be able to say that you could make a chart of air pressures for all the different rivet lengths and then just set the source regulator to the pressure for the rivet size you’re using at the moment and then not have to make any further adjustments. The reason I believe this is I have not found a pressure regulator to have all that fine of an adjustment. At the very least, any time you wanted to make an adjustment you would have to either be operating the gun, dry firing if you will, while you are adjusting the regulator so that you have some airflow. If there is no airflow, I have seen regulators that won’t show a change on the gauge until you turn the T-handle a full half of a turn. Another downside is to make any adjustment you have to cross the shop to wherever your air source regulator is located. In a lot of shops that may not be very far but in others it is.
With method one all that is required is a couple seconds to make a small adjustment on the flow valve and then back to riveting.

To each his own… The primary thing is to find a method that works. I offered my method as one that I have taught a lot of other people that were struggling and it totally solved their problems.
Like I said already, I think a lot of the negativity about the airflow control is that there are lots of people that have used the piece of junk ball valve. It is virtually impossible to make the necessary adjustments needed if using one of those on a rivet gun.
Here is a link to the one that I have been using for more than 30 years on all rivet guns I use.

https://www.cleavelandtool.com/collections/riveting-and-bucking/products/inline-air-flow-restrictor
 
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The primary thing is to find a method that works.

Absolutely.

I offered my method as one that I have taught a lot of other people that were struggling and it totally solved their problems.

I'm guessing there are a few thousand builders who would kill to get personal instruction time with you. Seriously.
 
I'm guessing there are a few thousand builders who would kill to get personal instruction time with you. Seriously.
I'm one of them. Even though I've already build a tank, I'm finishing my second one and ended up watching his tank building video. So much knowledge. I feel more prepared doing that one than the first one I build and it's not based on the experience from the first one.
 
I'm one of them. Even though I've already build a tank, I'm finishing my second one and ended up watching his tank building video. So much knowledge. I feel more prepared doing that one than the first one I build and it's not based on the experience from the first one.

I think another video along the lines of the tank build video is in order but about riveting tips and tricks....:)
 
Compressor size

I blew up my 25 gal, loud-***, compressor and looking to replace w/ California Air model. 8 gal seems plenty for rivet, etc.... Not going to paint w/ this one..
Thoughts on size? TIA
 
Count Me In!

I'm guessing there are a few thousand builders who would kill to get personal instruction time with you. Seriously.

Our biggest mistakes come during riveting. It would be a huge benefit!

I think another video along the lines of the tank build video is in order but about riveting tips and tricks....:)

Short of Dan's idea, Glenn's idea sounds intriguing.

Mike
 
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