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Machined pengun - Dimply

Discuss miniature cannons built from things such as pill bottles and pen caps.
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Machined pengun - Dimply

Unread postAuthor: LeMaudit » Fri Jun 10, 2011 3:00 pm

Hi guys,

Here's my very first pneumatic project, following a design JSR was kind enough to help me design and approve.
(guess who's fault it will be in case of failure?)

I'm happy to present you:

DIMPLY, the over engineered pengun
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Well, that's the hypothetical and completely virtual 3D goal, of course... need some real work to do now ;-)

It will be able to fire 1/8" tiny ball bearings. Hopefully using pressure close to at least 400 psi (my shock pump limit).
I have also prepared a plan with all the sizes, and I hope dewey1 or any 3D enthusiast will grab the pengun plan by its balls and make a cut drawing from that ;-) My 3D preview is really not more that a few rods and holes. Nothing is detailed internally. But I compensate the lack of detailed work using a shiny texture (in doubt, be shiny...)

Dimensional plan: 1 pixel = 1/10mm
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Here's a great sectional view made by dewey1:
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My intention is to post both picture results step by step, but also movies on YouTube showing the building process, so if you are curious about how someone that never learned of to machine properly can make a fool of himself right in front of a camera, please subscribe to this thread :-D

I hope you'll enjoy what will follow.

Note: As a respectful homage to The Master, there's tiny amounts of epoxy used

For convenience to group all that I'll post following this thread, here are all the steps, video and cutting plans:

Step1: Video Plan
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Step2: Video Plan
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Step3: Video Plan
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Step4
: Video Plan
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Step5
: Video Plan
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Step6: Video Plan
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Step7: Video Plan
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Step8: Video Plan
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Step9A: Video Plan
Step9B: Video Plan
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Step10: Video Plan
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Step11A: Photo1 Photo2 Photo3 Plan
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Step11B: Video Plan
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All the parts done
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thanks to dewey-1 for the beautiful 3D work!

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Step12: Video
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Shooting tests Video
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Last edited by LeMaudit on Sat Jul 30, 2011 5:49 pm, edited 16 times in total.
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Unread postAuthor: warhead052 » Fri Jun 10, 2011 3:08 pm

This is going to be pretty cool when completed I think.
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Unread postAuthor: ramses » Fri Jun 10, 2011 3:55 pm

How do you intend to do the dimples? Ball mill and rotary table?
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Unread postAuthor: LeMaudit » Fri Jun 10, 2011 4:08 pm

This is going to be pretty cool when completed I think.


I'll try to fulfill your expectations :D

Ball mill and rotary table?


Exactly!
I have cutting plans done, I will post them in parallel with the photos and videos so people interested can follow the building pretty much as if they were over my shoulder ;-)

And I'll be happy to read about criticism and suggestions for improvement of course. As I said, I'm pretty much self-taught, and my technique leave much room to improvement.
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Unread postAuthor: POLAND_SPUD » Fri Jun 10, 2011 4:13 pm

JSR ji##### his pants in 3.... 2.... 1.... :D
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Unread postAuthor: ramses » Fri Jun 10, 2011 4:29 pm

Do you plan on using a tailstock with the rotary table, or do you think it'll be ridged enough?
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Unread postAuthor: exotechmaster » Fri Jun 10, 2011 4:35 pm

looks mechanically sound on your blueprints
micro piston setup is so cool,
using the pilot as a pressure release trigger is nifty in something so small


what is your estimate on the range of this wee beasty
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Unread postAuthor: LeMaudit » Fri Jun 10, 2011 4:56 pm

JSR ji##### his pants in 3.... 2.... 1....


He'll be okay... he saw the design already... ;-)


Do you plan on using a tailstock with the rotary table, or do you think it'll be ridged enough?


I just hope it will be rigid enough :-D I don't have a tailstock attachment for the mill... though this could be a VERY good reason to buy one ;-)
The dimples are only 0.3mm deep, that's not much, I think it will be okay.

using the pilot as a pressure release trigger is nifty in something so small


Many members here made designs very similar if not identical to this one. Nothing really new. It's just for me a way to combine things I like: miniature, gun and pressure! The range I have no idea, it will not be that impressive in term of power I think... maybe going through a tin can? That's my best hope. You'll see some slo-mo for sure! (well, if the darn thing fire :? )

The goal for me is to start doing something pneumatic for real... my next project will be something of a different level completely... but that's too soon! :D
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Unread postAuthor: al-xg » Fri Jun 10, 2011 7:06 pm

Oooh I like the magnet !

A chamfer on the magnet might be a good idea, as I imagine it will be glued on. The piston has quite a short bearing surface when in forward position so, unless you have quite a tight tolerance, it might mean the magnet could touch the barrel seat.
As I'm sure you can achieve quite a good tolerance, maybe a simple scratch down the side of the piston or bore will be enough for filling.

How are you going to do the cuts on the barrel support, drill first then turn down ? Or just a 4mm cutting head ?


One thing you could try is making a rifling button, a rifled pen gun would be amazing ;) Mmm or maybe save that for a bigger project !

Mmm in fact I should try and convince someone to machine me a rifling button, accuracy will always be limited if I making my tools with a dremel.
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Unread postAuthor: LeMaudit » Fri Jun 10, 2011 7:44 pm

al-xg wrote:A chamfer on the magnet might be a good idea, as I imagine it will be glued on.

Damn! You found the secret place where the epoxy will be... ;-)
neodymium magnet edges are a bit rounded. It should be okay. It will be pushed gently in place anyway, as the pressure increase below.

The piston has quite a short bearing surface when in forward position so, unless you have quite a tight tolerance, it might mean the magnet could touch the barrel seat.

The tolerance should be very tight (I'll turn the diameter to custom fit whatever hole I drilled) and the magnet fit inside the barrel, so no problem if it is pushed a bit inside.

How are you going to do the cuts on the barrel support, drill first then turn down ? Or just a 4mm cutting head ?

A 5/32" end mill cutting on the side. I'll describe that in details. For now I've almost finished filming the first step, I am learning how to make a niceeeee video out of it.

More this week-end.
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Unread postAuthor: inonickname » Fri Jun 10, 2011 8:43 pm

Personally I'd simplify the piston...but at least its serviceable so you can fix it later if it fails :P

Looking good!
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Unread postAuthor: ilovefire » Fri Jun 10, 2011 9:48 pm

commenting so i can get emails on the updates, but i may as well say it looks like a fantastic design and i would be completely happy to give the end result a home out of the kindness of my heart 8)
i think you have motivated me to get of my but and go fix my pen gun i make from a parker pen
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why make it if it dosent shoot?
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Unread postAuthor: jackssmirkingrevenge » Sat Jun 11, 2011 2:51 am

Finally, the curtain goes up :) but "Dimply"? lol.

exotechmaster wrote:what is your estimate on the range of this wee beasty


With pen guns, "across the room" is the best you can hope for :)

He'll be okay... he saw the design already... ;)


Yep, we've been brainstorming for a couple of weeks, mostly yours truly saying what I want to do and LeMaudit pointing out what can and can't be done, as well as trying to add as many threaded sections as possible and eliminating use of epoxy :D

I've seen the cutting plans and they are fantastically detailed, looking forward to seeing this take shape!

As I'm sure you can achieve quite a good tolerance, maybe a simple scratch down the side of the piston or bore will be enough for filling.


I don't think that will be necessary, without an o-ring it's not going to be a 100% seal anyway.

One thing you could try is making a rifling button, a rifled pen gun would be amazing


Rifling on a device that doesn't even have sights seems a bit redundant, but it would be interesting to achieve...

Personally I'd simplify the piston...but at least its serviceable so you can fix it later if it fails


We've been though several designs, this was my last one and I think it is the most elegant as it saves the need to cut a groove in the face of the piston to fit the o-ring while neatly incorporating the magnet to keep the prrojectile from rolling out.

My one doubt is the o-ring seals for the threaded sections, but if in doubt, Araldite ;)
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Unread postAuthor: ilovefire » Sat Jun 11, 2011 3:26 am

jackssmirkingrevenge wrote:
exotechmaster wrote:what is your estimate on the range of this wee beasty


With pen guns, "across the room" is the best you can hope for :)


iv hit my neighbors shed from at least 30m away
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Unread postAuthor: al-xg » Sat Jun 11, 2011 5:10 am

I don't think that will be necessary, without an o-ring it's not going to be a 100% seal anyway.

On the machined QEV I didn't get to finish, the max gap (on the diameter) between piston and the hole was intended to be 0.075mm, and the min gap 0.025mm with an N6 surface finish (Ra 0.8μm / 32μinch).
I did not want to post this after realising how creepy it was ;) (that steel bung, is just a fixture for machining, it is not part of the QEV design)
With any sort of lube on that, filling would be painfully slow or not even work.

Rifling on a device that doesn't even have sights seems a bit redundant, but it would be interesting to achieve...

I'm pretty sure oblong projectiles would tumble within the effective range of the pengun, it's not really about accuracy just keeping projectile tip forward.
It would be pretty useless on the ball bearings though.
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