DMS Delay tool - simplified

[kramer714]

It it surprising how many people are still confused about how to set up an Aerotech DMS delay adjustment tool. Also, less surprising is how many people borrow stuff at a launch and forget to return it. My DMS adjustment tool is a great example. So, my solution is...

3d printable NON ADJUSTABLE delay tools. Each tool ONLY drills a preset delay, I designed and printed a 2,4,6, and 8 second delay. the 3d printed tool loads a stubby threaded drill. These are very commonly used at the day job (aircraft development), importantly the distance from the threaded shank to the tip is the same for every drill of that size. Print - put in drill and tighten nut - no adjustment. There are 'notches' printed into the tool to tell how many seconds it removes. The drills are a few dollars a piece in a 10 pack.

 

[cwbullet]

Nice design. I can't wait to see more. Is this the same thing:

https://drillsandcutters.com/50-cob...4HHkhB9Wvd_EmhIHc5wfFWCGYL20ZIeBoCMPwQAvD_BwE

 

[kramer714]

Im using #20 x 1-1/4 thread hex shank threaded drill

 

[kramer714]

The dimensions on the side view are the distances in MM from the tip of the drill to the 'flat' that hits the top of the charge well, and the corresponding time. 27.9 6S for example is 27.9 mm tip to flat = 6 seconds. I'm showing that so you can check the length of what you print to make sure the times are correct. I measured the lengths from a Aerotech delay tool.

 

[dpower]

3d printable NON ADJUSTABLE delay tools. Each tool ONLY drills a preset delay, I designed and printed a 2,4,6, and 8 second delay.

To clarify, do you mean -2, -4, -6, -8 seconds? Most DMS have a minimum spec of 6 seconds, starting at 14.

Great idea!

 

[cwbullet]

To clarify, do you mean -2, -4, -6, -8 seconds? Most DMS have a minimum spec of 6 seconds, starting at 14.

Great idea!

I have to agree. I plan to test this out also.

 

[kramer714]

I have to agree. I plan to test this out also.

Yup, they are -2 seconds, ( a 14A would become a 12), -4 seconds (a 14A would become a 10) etc. DMS have 14A delays.

 

[COSTransplant]

Im using #20 x 1-1/4 thread hex shank threaded drill

Do you have a link to where to buy the correct shank/drill so that it matches the 3D creation? Is that a stupid question? :-(

 

[cls]

Mike, creative genius! Very cool.

 

[kramer714]

I buy them from ebay, but equivalent to https://www.mcmaster.com/8824A53/

 

[augendoc]

I took Kramer714's brilliant idea and remixed the 3D parts, primarily because I couldn't find the same size drills that he used. I put ribs all around the perimeter for a better grip and embossed the number of seconds each tool removes. My pics show the number of seconds removed as a positive number. In the attached STL files I added a minus sign so it's clear the number indicates WHAT YOU'RE REMOVING. I also color-coded mine.

I've included a pic of the drills I bought: 1 5/8" exact total length, #7 size (0.200", 13/64", 5.08mm), 135° split tip, 1/4-28 threads, 120° bevel on the upper end of the 5/16" hex. I just bought the drills on eBay from this guy: https://www.ebay.com/itm/353418250410. Price was $1.00 per bit, new with free shipping. If you use a different length of drill you will have to remix the 3D prints to get the correct length. After testing to confirm the proper drill depth, I secured the nuts with blue thread-locker. You could also pour epoxy into the open hex portion to secure the bits, but I figured I might need to re-do the 3D prints at some point so I kept that option open.

The 1/4"-28 flange nuts I bought here: Amazon. They are 25 for 9.99 so I have 17 left that it will probably take me a lifetime to use on another project, being the odd size and all.

 

[roytyson]

I took Kramer714's brilliant idea and remixed the 3D parts, primarily because I couldn't find the same size drills that he used. I put ribs all around the perimeter for a better grip and embossed the number of seconds each tool removes. My pics show the number of seconds removed as a positive number. In the attached STL files I added a minus sign so it's clear the number indicates WHAT YOU'RE REMOVING. I also color-coded mine.

I've included a pic of the drills I bought: 1 5/8" exact total length, #7 size (0.200", 13/64", 5.08mm), 135° split tip, 1/4-28 threads, 120° bevel on the upper end of the 5/16" hex. I just bought the drills on eBay from this guy: https://www.ebay.com/itm/353418250410. Price was $1.00 per bit, new with free shipping. If you use a different length of drill you will have to remix the 3D prints to get the correct length. After testing to confirm the proper drill depth, I secured the nuts with blue thread-locker. You could also pour epoxy into the open hex portion to secure the bits, but I figured I might need to re-do the 3D prints at some point so I kept that option open.

The 1/4"-28 flange nuts I bought here: Amazon. They are 25 for 9.99 so I have 17 left that it will probably take me a lifetime to use on another project, being the odd size and all.

So I printed augendoc's design, and ordered the drills from his ebay supplier. Ebay transaction was quick to ship, and prints turned out nice.

I do want to trust them, but will not until i verify the drill length against an actual DMS tool.

Word of cuation, there are at least three different drill recomendations in this thread, and the are ALL different length of drill bits. The ebay's recomended above are 1.6" long, McMasters is 1.5" long, and DrillandCutter says theirs is 1". There is no way they will all be acurate with differing drill lengths. My hope is that augendocs design is made around the length of the drill he purchased.

Trust but verify....

 

[augendoc]

I hear you on the different drill lengths in this thread. I did the CAD design after I got the aforementioned drills in the mail and there was some tweaking of the design to accommodate the inherent spreading of 3D filament material when printed. I measured the drill protrusion beyond the bottom of the knurled plate and they were accurate in most cases to 0.001” on average.

The amount of protrusion was calculated from Aerotech’s published CAD design for 29mm DMS motors. The well for the ejection charge is 0.5” diameter by I think 0.75” deep. Add another 0.125” for the thickness of the material at the bottom of the well plus there appears to be a gap between the back of the well and the face of the delay grain. I will confirm those measurements tomorrow when I‘m at my computer, but I believe the total distance from the front of the ejection well to the face of the delay grain was 0.925”. Aerotech states that the delay material burns at 1/32” (0.031”) per second, so for example a 2 second removal bit should drill out 0.062” of material. Add that to the base depth to the delay grain face of 0.925” and the -2 drill should protrude 0.987”.

The drills I linked to were 1.625” total length. The knurled platform needs to have some thickness to deal with the 120 degree bevel at the base of the threads, plus enough that the flange nut will be flush with the end of the threads when tightened. That left a knurled plate depth of ballpark 3/16” for the -8 sec drill. If your drills were only 1.5” long instead of the ones I found, that plate would be only 1/16” thick.

Everyone should note that these aircraft drills come in several different formats. Mine had a 5/16” hex base. @Kramer714’s STLs were for a slightly larger hex, I think 3/8”. Some drills do not have the 120 degree bevel at the top. And other drills have a square drive instead of a hex. Finally, i think there is a lot of error or confusion as to what constitutes O.A.L. (Overall length). Is it the length of the entire bit from beginning of thread to tip of drill, or beginning of hex to tip, or base of hex to tip? It's supposed to be the total length of the entire bit, but I don't think some vendors do it that way.

If someone says they made these using a 1” OAL drill, there must be a measurement error somewhere. A -2 second drill would have to extend 0.987”, so if the OAL of the drill was 1”, then only 0.013” of the threads would be screwed into the knurled plate. At a thread pitch of 28/inch that’s less than half a thread, so I don’t buy it.

Because of the potential for confusion, my recommendation is buy the drills first and once you have those in hand, do the math, make your print, assemble, then measure and verify.

 

[augendoc]

Attached is the Aerotech drawing for their DMS motor assembly. The annotations in red calling out the dimensions of the forward closure are mine. The well inner diameter is 0.5", depth 0.75" and depth from forward end to delay grain is 0.925".

My delay drill .STLs are based on that measurement. If you have a DMS motor handy, you should be able to confirm the drill depth of your printed tool by sliding the desired delay drill into the forward closure until it bottoms out against the delay grain. Then measure the gap between the front of the forward closure and the bottom of the delay drill plate. The gap should correspond to the number of seconds of delay removal x 0.031". This is similar to the process Aerotech outlines for calibrating the proper depth of their RMS delay drill.

I don't have a DMS motor handy, so real field measurements and a confirmatory field test would be greatly appreciated. If I screwed up any of these measurements please let me know and I will re-do the STLs, cleaning them with my tears as I go.

I found some small plastic caps to slide over the drill tips to protect them from damage. Pic attached.

 

[kramer714]

Very Nice - Always good to se someone do improvements on my design. Well done!

Yeah, good to have the drills before making the parts, measure the length.

Mike K

 

[86mustang408w]

Ok, that's cool!

I got my L1 on 11/4/23. I bought one H135, and grabbed a delay drilling tool for myself because I knew I'd need one. I was thinking when I get a 3D printer I'll measure the 2 second washer, cut the measurement in half, so I can use one second adjustment increments over 2. Then thought If I could make another tool to calibrate and adjust the bit from 13sec to to as low as I need. In 1 sec increments, that would be perfect for me instead of the yellow tool and washer. I like a lot of thoughts and ideas here, thanks.