M

mlwynn

Well Known Member
Hi All,

I was merrily dimpling away at my wing panels with a DRDT-2 this last weekend when the piece of steel that is the functioning lever broke. Needless to say, the work stopped. I dropped a quick email to Paul at Experimental Aero. Immediately, essentially no questions asked, he shipped me a new piece (should arrive today). We then got into an email conversation about how I was using or misusing the equipment. The key question is, how much pressure should you use to dimple?

I started out with pretty moderate arm pressure while dimpling my empennage skins. When riviting came around, I found a number of dimples that were not deep enough. Thereafter, I set up the dimpler such that I could pretty much put my whole (180#) weight on it as I dimpled. So, the technique was to get the male end through the hole to be dimpled, bring the lever down to where the female part was just engaged and then (more or less) pounce on the lever. Paul believes, and is probably correct, that I am using excessive force.

Part of my personal problem is that I don't have a lot of upper body strength. I use my weight and a little momentum to compensate for that. So, I wanted to circulate the question, how much pressure do other folks use on their dimpler? What is enough and what is too much?

The DRDT-2 is a great machine and I can't say enough good about Paul Merems and ExperimentalAero. Absolutely first class service and response. He and I are trying to figure out if there was a defective part or an abusive owner. Thoughts?

Regards,
Michael Wynn
RV 8 Wings
 
Last edited:
mlwynn said:
Hi All,

Thereafter, I set up the dimpler such that I could pretty much put my whole (180#) weight on it as I dimpled. So, the technique was to get the male end through the hole to be dimpled, bring the lever down to where the female part was just engaged and then (more or less) pounce on the lever. Paul believes, and is probably correct, that I am using excessive force.Regards,
Michael Wynn
RV 8 Wings
Click to expand...

Holy jeez. I'm sure someone can supply the formula, but if you're putting 180# of weight on the lever, then the concentration of pressure is huge over such a small footprint as the dies themselves.


It's possible that you might not have the dies adjusted properly and they may not be mating completely or even be off centered from each other a tad.
With the skins especially, it shouldn't take much pressure at all to get the dimple done.
 
I set my dies up so that they're touching with the lever all the way down, and then I go just a TOUCH more closed before cranking down the nut. The pressure is fairly light, and my dimples are more or less perfect as far as I can tell.

As always, YMMV.

-John
 
Same Here

I set mine the same as John.

Trying to look at this from a theoretical perspective, the dies do the dimpling. When the two dies are fully mated, they ain't goin no further, so to speak. Unless we want to talk about compressing aluminum and steel, which I don't think we want to do, there is no sense in putting more pressure on the machine once the dies are fully mated. So if you pull the handle all the way down, adjust the dies until they are fully mated, and then go a turn more, you should be good to go. In production, the work involved should be minimal and you should be able to merrily go along just pulling the handle easily as you go. It doesn't take much. If the leverage is not going over the top just as you bottom out on the handle, you have it adjusted too tightly.

My guess is that if you aren't getting consistent dimples, it probably is not due to a lack of pressure. More than likely the working piece is not positioned perfectly parallel to the dies. Check your table to make sure the piece is laying completely flat and parallel on the die.
 
Check the dies

There have been some reports of dies not mating quite right - you may want to check yours to ensure that's not the case.
 
I learned this the hard way....

1. Be sure to adjust the bottom plate to align perfectly with the top. Put a die set in there and watch the dies come together to make sure that the pin on one die is in the center of the other. Once adjusted, the lower alignment rarely goes out, but I ckeck it periodically.

2.Adjust the depth so that you are at the end of the stroke. The linkage develops the most leverage at the end of the stroke, and if adjusted properly, it does not take much force on the handle to develop sufficient force on the dies.

**The handle should be down around 4-5:00 when the dies come together, if it is horizontal, you do have to put much weight into in and will not get a good dimple...it will also wear you out.
 
At least on my DRDT2, there is an point where the handle will 'flip' or pop - just a slight give of pressure (kinda like a torque wrench does). I set my length so that when the dimples are together it's right at this flip. To set the dimple I only have to pull enough to get the pop (ala torque wrench). Sometimes this has to be adjusted depending on the thickness of the material, but it always gives me a good dimple with minimal pressure.
 
DRDT2

Concur with the statements above. Dimpling with the DRDT2 takes no effort at all. I can produce perfect dimples if I hold the handle with two fingers. As ccrawford said, there is a little detent that you hit that signals a completed dimple. All you are doing if you go beyond that is stressing the components.

Antony
 
DRDT-2

As Mike had mentioned in his post, he had contacted me when the failure occurred. My immediate concern was to get him a replacement clamp in his hands as soon as possible (at no cost). Customer satisfaction is my main priority. My second concern was why did it fail. There are two possibilities. A manufactured defect? Possible overloading? Or both.

Mike is sending me the failed clamp handle for my failure review. I have not received it yet. However Mike did mention to me and in his post that he puts all his body weight into the clamp lever when dimpling. As mentioned by other owners, who have posted replies, it doesn?t take a lot of force to dimple with the DRDT-2. There is a stop pin that stops the handle travel. If the DRDT-2 is setup properly, as long as the handle hits the stop, the dimpling force will be consistent for every dimple. However if you continue to put additional force on the handle after it has hit the stop you will not increase the dimpling force. You will just tire you arm unnecessarily. If you continue to apply a good portion of your body weight to the handle, you may in fact cause it fail over time. This is possibly the cause of this failure.

There are hundreds of units in the field. The highest time (most number of dimples) DRDT-1 belongs to the Alexander Tech Center. I believe they have built over 200 empennage kits with the tool. The only other clamp failure reported (and replaced) was where a builder was using the tool to dimple hardened steel nutplates. The DRDT-2 was designed to dimple aluminum sheet and the thin soft stainless steel used in the firewall on RV?s. The DRDT-2 components have been thoroughly tested and meet the design specifications for the tool (under proper use).

If anyone has any questions about their DRDT-2 or DRDT-2?s in general just email me. If you are wondering about the performance and or quality of the tool, just search the forum or post a question. I am sure all the DRDT-2 owners viewing the forums would be glad to provide user input.

A tool that makes dimpling your RV parts easier, safer, quieter, more consistently, and less fatigueing is what the DRDT-2 is designed and built for.
 
Dimpling pressure

I just finished a dimpling session not two hours ago at Alexander Tech Center on their DRDT-1, and it functions perfectly. At the end of the stroke you just bump it overcenter and you're done! Theirs is a massive, welded I-beam C-frame setup which is very rigid. The ram is surprisingly free of any play in its housing bore after all the use it has been through.
 
Last edited:
My personal dimpling issues

To answer one question, yes my holes are reamed or drilled to #40 so the dimple die goes in fine. I have been using cleaveland dies, and they seem to fit perfectly.

It is now abundantly clear to me that the DRDT failed due to pilot error. I have been really cranking on the lever. I will have to send Paul a check to pay for the parts as it is just not fair to expect him to warrantee my misuse. :eek:

I thank you all for your insights and experience. This forum continues to be of immeasurable help for a new builder like me.

Regards,

Michael Wynn
 
Build On

Mike,

Consider it a lesson learned. As I committed, the replacement clamp is at no cost to you so please don?t send a payment. Customer satisfaction comes first.

The most important thing is that you receive the clamp, get it installed and get back to dimpling.
 
Recovering DRDT-2 Abuser

Paul asked that I retitle the thread so that it didn't pop up to a search looking like the unit failed. I tried to edit the thread title, but it doesn't seem to have edited. Anyone know how to do this? :confused:

Regards,

Michael
 
DRDT-2 Restored

Just to put a cap on this thread, I received the new parts from Paul last Friday. Took about ten minutes to put them in. I then set up the dimpler per everyone's advice above. Imagine my surprize when I got perfect dimples with gentle hand pressure. Boy do I feel stupid. It must be that "I don't need to stinkin' instructions" gene that some of us males seem to be born with. So, my thanks to everyone for their advice and to Paul at Experimental Aero for an outstanding product and even better support.

Michael Wynn
RV 8 (back to the wing skins)
 
You must log in or register to reply here.