cgrossl

cgrossl

Well Known Member
Over the last few months, I have been doing alot of research on building airplanes, RV's in particular and I have decided to build an RV7 for myself. But, I am waiting until I sell my truck before I buy the empenage kit. I need the garage space.

Anyway, during all of this research I found it surprising that the most accepted methods of pressing dimples in a piece of sheet aluminum are with a hammer and a C-Frame jig to keep the dies aligned, or with the pull of a lever. I'm sure that both of these methods work well, but I work as a Machine Design/Manufacturing Engineer so my mind kind of defaults to figuring out ways to automate processes. Its almost a reflex now.

Since I can be kind of lazy sometimes, my first thought after finding out that you had to use a hammer or a lever to make a dimple in a panel was to use a foot pedal operated pneumatic cylinder to do the work for you. This would give the operator both hands to position the panel and wouldn't require him or her to have to over extend when dimpling large panels. Also, since the air cylinder would exert the same amount of force on the dies every time, dimples should be very consistent.

So, I sat down and designed a foot pedal operated, pneumatic dimpler. The preliminary design is complete and I should have the prototype built in the next month or so. It completely bolts together (No Welding), weighs a little less than 30lbs, has a 23" throat (to dimple up to 46" wide panels), uses standard 3/16" shank dies, and uses high quality pneumatic components capable of exerting 300lbs of force. The whole thing was designed using SolidWorks 3D modeling software. Cosmos Design Analysis software was used to evaluate the design to ensure that the unit flexes as little as possible during operation. We'll see how well I did after the prototype gets built. For some reason, everything looks better on paper than it does in the real world. Right now, retail price looks to be in the $350-$400 range for a complete kit the includes everything except dies and an air nipple. Assembly should only take about half an hour. I am also looking at producing dies. $35 seems like a whole lot of money for two little pieces of stainless steel.

So, what does everybody here think? Is this something that you would be interested in, or am I wasting my time?

By the way, if anyone here is looking for a good looking 1972 Chevy Truck, shoot me an email or PM.

Thanks,
Cameron
 
Avery Tools

Avery Tools has a foot air operated dimpler. Kinda spendy...
Vans sells a RV QB Kit to people that want an airplane, not a job. Very little dimpeling in that. Get a QB and fly sooner!! not later.
 
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Cameron,

My EAA chapter has a foot-operated pneumatic dimpler that was surplus from Lockheed. We love it! Once you try it, you'll never want to use a hammer and "C" frame. It's one of the most popular tools in our shop.
 
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Aircrafters sells a giant yoke. I wonder how many they sell.
squeezeryoke_b.jpg

I am not affiliated with AirCrafters in any way.
 
Say again?

cgrossl said:
............This would give the operator both hands to position the panel and wouldn't require him or her to have to over extend when dimpling large panels........ It completely bolts together (No Welding), weighs a little less than 30lbs, has a 23" throat (to dimple up to 46" wide panels), uses standard 3/16" shank dies, and uses high quality pneumatic components capable of exerting 300lbs of force......the unit flexes as little as possible during operation.....retail price looks to be in the $350-$400 range for a complete kit the includes everything except dies and an air nipple. Assembly should only take about half an hour...Is this something that you would be interested in, or am I wasting my time? ........
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Cameron,

Much of what you describe has for decades been in common use in the production environment. In addition, the concept is also frequently employed on the factory floor to set rivets, both flush and protruding.

Your design sounds interesting and if you can produce a high quality pneumatic dimpler/riveter and manage to bring it to market in the target price range you hope for, I say go for it and go for it in a big way. As one lister already suggested, its utility would be lost on the average quick builder but such a tool if properly designed and competively priced would have wide appeal in the world of amateur sheet metal aircraft construction, RV or otherwise.

I'm not convinced you can produce a reliable pneumatic tool that can measure up to the standards of the pneumatics out there and already enjoying widespread use. You'd be hard pressed to find many of those tools in basic form and new condition for the price you are shooting for especially since you mean to include the substantial and expensive throat accessory to be bolted to it and the floor frame to complete the assembly. My uneducated guess is such a design would of economic necessity have to cost much more than $400 for you to realize any profit worth pursuing.

Clever designs are developed by creative people all the time. However, as time has shown us again and again, it is one thing to design something that people want but a completely different set of skills and talents are required to make the transition from paper concept to hard metal creation and then compete successfully in the bare knuckles forum of the marketplace.

It is your vision. None of us can pretend to know what you are capable of. If you are convinced you can deliver such a product at the price you specify, AND after reading of its positive and glowing reviews in the aviation publications, I'll likely be placing an order and consider it the best $400 I ever spent.
 
cgrossl said:
... It completely bolts together (No Welding), weighs a little less than 30lbs, has a 23" throat (to dimple up to 46" wide panels), uses standard 3/16" shank dies, and uses high quality pneumatic components capable of exerting 300lbs of force. The whole thing was designed using SolidWorks 3D modeling software. Cosmos Design Analysis software was used to evaluate the design to ensure that the unit flexes as little as possible during operation...
Click to expand...
I think you'll find that the force required to make an acceptable dimple is considerably higher than 300 lbf, perhaps on the order of 5 to 10 times that.
Your frame will need to resist significant deflection at those loads. Make sure you fully know the problem you're trying to solve first. Otherwise an inexpensive air operated dimpler would surely be purchased by some.

-mike
 
Air Dimpler

Well, a lot of folks said it wouldn't work...but one of our TVRVBG (Tennessee Valley RV Builders Group) members modified an Avery C-frame with two small (Bimba) air cylinders and an off-the-shelf air operated pneumatic pilot valve. Place the clear tubing in the mouth, position the aluminum sheet on the dimple die, a gentle puff of air with the mouth, and Voila! A neatly dimpled hole.
There's no telling how many holes this particular unit (Ole Yeller) has dimpled, but a good estimate is that it's been used on at least 6 RV's...and it's currently on No. 7!
The designer/builder of the pneumatic dimpler was going to make his mod available as a retro-fit kit, but he put all his time into building an RV-8, and he's not interested now.
I'd guess he didn't have over $50 (plus the original C-frame) in this dimpler.
Don
 
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Aircrafters Yoke

I have large Aircrafters yoke that I picked it up used at the fly market several years ago during Oshkosh.

The yoke is flame cut from 1? steel and weights 105 lbs. I set it up with a foot pedal air valve to a CP squeezer and it works very nice for dimpling. It will also squeeze small 3/32? rivets but flexes when squeezing 1/8?.

One caution, it is very easy to put dimples in places you don?t want them.


Don
D Pansier
Green Bay, WI
RV-7, Finish Kit
N450DP Reserved
VAF 586
 
I think the big obstacle is the pressure required and the resulting deflection of the frame. Has anybody considered a device that automates the "whack" of the usual c-frame tool? I'm picturing a c-frame with something like a pneumatic nail-gun attached to the top. It seems that this arrangement would completely avaoid having to beef up the frame.
 
You all bring up some good points. I do wonder if 300lbs will be enough. I must also clarify that I am working on a dimpler only, not a riveter. I also wonder how much my C-frame will flex. But, there's really only one way to find out and that's to try it and see. I actually look forward to being able to design and build something to see if it will work, then, getting to refine the design. I'm used to getting one chance. I work for a company that designs and builds custom machinery, mostly for automotive manufacturers. One week, I'll be designing a weld fixture then the next week I'll be designing an 80 ton, air over oil press, complete with tooling and auto part loading and unloading. Working for this company gives me access to an awesome machine shop and allows me to purchase steel and pneumatic components at OEM prices.

Designing a machine to do a specific function is nothing new to me, but bringing it to market is, and that's where my hesitation lies. Right now, I plan to build a working prototype, test it myself, then let a few local builders test it out. I also have an idea that would all but eliminate missing the rivet hole with the dimpler, but it would require a custom set of dies, which could be a good thing and it could be a bad thing.
 
Not the first

Someone else tried the same thing a while back on this forum-------I.E., "testing the waters" for a pneumatic dimpler.

As I recall it wasnt well recieved. First rendition had one cylinder, then he added a second. Was talking around the $500 area. Foot pedal valve unit was low end, needed a "Teasing" valve.

If I remember correctly, the unit was an add-on to the DRDT-2.

I tried searching for it, no luck.

If you are going to develop something like this, I wish you good luck.

I think the market is out there, price and quality will be the determining factors, IMHO.

Mike
 
cgrossl said:
Anyway, during all of this research I found it surprising that the most accepted methods of pressing dimples in a piece of sheet aluminum are with a hammer and a C-Frame jig to keep the dies aligned, or with the pull of a lever.
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Cameron, while I believe there is always room for innovation, don't downplay the advantages of the hammer or lever-methods. Both require no noisy compressor, and the lever method (e.g. DRDT-2) is near silent allowing us to build away in our garages into the wee hours of the night w/o waking family or neighbors. Just food for thought. Good luck!
 
Brad,
I'm not trying to downplay the regular methods of dimpling panels, but I can see where you might have taken my initial post that way. It just really surprised me that no one had brought a more automated way of dimpling panels to the market. By nature, airplane builders are innovative people and what I'm proposing is a very simple idea. I did find some instances where individuals had made working, one off, dimplers, but I didn't find a commercially available, fairly inexpensive unit.

I've not got a whole lot going on right now so this idea has been running around in my head for a while now. I think that I can do this for the price that I gave in my initial post. We'll just have to see if I'm right. I may be trying to tackle way more than I am thinking.
 
Pneumatic Dimpler

Cameron,
It's not just the force but the rate at which the force is applied. The dimpler (Ole Yeller) I referred to in my previous post had two BIMBA cylinders which were, IIRC, 1 1-2 inch diameter cylinders. If my math is correct, that's about 1.8 sq inches per cylinder and at 80 psig shop pressure, that results in a force of a little less than 300 lbf. By adjusting the air pressure with the pressure regulator, we could get a quick WHACK or a more gentle TAP. I can't remember the exact air pressures, but my shop air pressure can be regulated up to 125 psig, and I never had to take it that far.
I wish you well, but I really think that as many C-frames as there are out there, you would be able to market a retro-fit kit better than a new dimpler using a new frame.
But hey! What do I know? I'm just a rocket scientist!!!
Best wishes,
Don
Also, you should consider the safety of such a device. As smart as we are :D , there's always the possibility that someone could try to dimple their finger! :eek:
Having used a pneumatic dimpler myself, I will say it's easier to do that with a pneumatic dimpler than with a hammer type.
 
Don,
How about posting some pictures of Ole Yeller? Might put one in the queue for right after I finish the propeller duplicator <g>

Dan
 
photss

DanH said:
Don,
How about posting some pictures of Ole Yeller? Might put one in the queue for right after I finish the propeller duplicator <g>

Dan
Click to expand...
Dan,
I'm not in possession of Ole Yeller anymore, and I'm not sure I have photos. I will look when I get home and if I have some photos, I'll see if I can post them.
Don
 
Yes we want them

Buying a pneumatic squeezer, dimple or rivets is one of the best tools I bought, but I think it has been done already. Good idea though :D
 
Okay, here's a question for the rocket scientists out there. How many unwanted dimple holes does it take to ruin a skin? My guess would be "one", but why not have a way of insuring against even that? I'm too stupid to do it, but I'd like to see someone take a regular male dimple die, and put a tiny hole through the center of the pin for a tiny fiber-optic light. There would be a reciever in the other die, and an electrical lock-out solenoid on whatever kind of dimpler you are using. If the hole isn't aligned over the pin, no dimple! Oh well, yeah, I know, dumb idea......
 
Don,
I like the retrofit idea. But, from the regular C-frame pictures that I have seen, the structure looks pretty flimsy and my calibrated engineering eye (yeah right) tells me that a 300lb force that trys to open the c-frame up would cause quite a bit of flex. Did Old Yeller flex alot during operation? The bracketry that would be required to do the retrofit would be extremely simple to design and manufacture.

As far as safety goes, yes, there is a major pinch point that would have to be guarded by a simple clear plexiglass guard.


Ron,
I have an idea for a mechanical way to ensure that the operator doesn't miss a hole while riveting. But, I figure that I'll see if what I've got works before I go down that road.
 
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dimpler-Private Message

Cameron,

I just sent you a private message that I hope will help you with your project.

Paul
 
cgrossl said:
Don,
... But, from the regular C-frame pictures that I have seen, the structure looks pretty flimsy and my calibrated engineering eye (yeah right) tells me that a 300lb force that trys to open the c-frame up would cause quite a bit of flex. Did Old Yeller flex alot during operation?...QUOTE]

Cameron,
Others have surmised in these forums and in the old Yahoo Groups that the C-frame is flimsy, but after over 6 RV's being built with "Ole Yeller," she doesn't seem flimsy to me...and I used it on my empennage. It's easy to say it looks flimsy, but my Registered Professional Engineer eye (BSME and MSME plus Professional Engineer) tells me it ain't flimsy. I've seen some folks try to convince me it flexes using bending moment calculations, etc. If she were flimsy, don't tell all those folks who are now flying their RV's that their rivet holes were dimpled with a flimsy dimpler frame. :eek:
It's like Jay Pratt said on an earlier post, we need to be building instead of spending so much time on these PC's...so we can go fly! :D
Don
BTW, if it means anything, I am planning to buy one of Paul Merems's DRDT-2 dimpling frames. Looks like a good design to me. When I had a break in my building schedule due to my Dad's stroke and subsequent death, someone else needed Ole Yeller to start their RV-8. Ole Yeller is a loaner for our builder's group and she's sorta like Van's Ole Blue (RV-6A). She just keeps goin' and goin'.
Click to expand...
 
Don,
I've been around enough to know that just because something looks flimsy, doesn't mean that it is. That's why I asked you if you saw alot of flex. You can caculate bending moments all day and you still won't get a better test than one in the real world. Just because the C-frame looked flimsy to me, doesn't mean that it really is. I've been wrong many times in my life and I'm sure that it will happen many more times before I die.


By the way, the "calibrated engineering eye" remark that I made about myself in an earlier post was meant to be in a sarcastic, poking fun at myself, tone, not an I'm smarter than everyone else tone. Just in case some took that the wrong way.
 
I bought a Kearns metal works c frame pneumatic dimpler about 15 years ago. It was similar to an avery in that it was made from steel tube. It had a foot actuated switch, and about all it would dimple deep enough without flexing was .015 elevator skins. In addition to it's miserable dimpling capacity was the fact that I was faster with a hammer and the traditional c frame due to the time it took for the pneumatic switch to reset for another lousy dimple.
Jay's right, quit trying to reinvent the wheel, get off the net and get in the garage and build!!!

Jon
RV4, RV4, RV6A, RV8
 
I admire the innovation behind the original idea, but I see it as significantly inferior to a DRDT-2. Points supporting the DRDT-2 include:
1) DRDT-2 costs much less at $330
2) Practically no noise
3) Very precise teasing and control using my arm and a lever - can't beat thousands of neural processing steps via coordination circuits in the posterior brain that refines signals to the muscles of the arm as I sneak the dies together and slide the pilot hole onto the male die before compression. While I can gain a little teasing with a pneumatic trigger, it is tricky and far less smooth. That's why I've never punched an accidental hole with the DRDT-2 but have with the pneumatic squeezer. Even my 12 year old son has dimpled with the DRDT-2 - no way he is touching a pneumatic squeezer.
4) No compressor needs to be running
5) No speed advantage of a pneumatic dimpler (might be slower due to more care to ensure alignment of pilot hole and dimple die). I can average close to one dimple every 1.5-2 seconds on the DRDT-2.
So, having bought and used the DRDT-2, I just can't see how a more expensive pneumatic dimpler would benefit the homebuilder who only needs it in limited spurts. A mass production scenario might be another matter to mitigate that famous occupational health diagnosis of 'repetitive stress injury'.
Just my 2 cents, and I certainly laud your innovation and enthusiasm.
 
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