QF 25 Pounder Build

[Caleb Smith]

I'm in on this hobby too!  After Tyng Industries offered a half built artillery piece for a very reasonable price, I just couldn't refuse.  So, now I'm the proud owner of a half built 25 pounder that needs rotate and elevate.  I would like to get this ready for the next battle, so I'll be hurrying along. 

In the last two days, I think I've figured out the elevate system.  Basically, it's just a standard servo with an extension on the horn with a piece of wire running from the horn to the gun platform.  The servo has plenty of movement to get to the 10 degrees maximum elevation, plus plenty of down angle.

I've attached a photo showing the basic idea.  If you guys think it will work, I'll replace the wire with a wooden pushrod system.

Thanks,

Caleb

[jvragu47]

Caleb,
            My first tank, T-12, the Pz IV used a servo for the elevate for years. It will be fine for the upcoming battle. Can't wait to see your  project finished.

John P.

[Caleb Smith]

Ok, that's good to hear.  I'll start working on installing everything today.

Next up, rotate!

Caleb

[Caleb Smith]

I got the wooden pushrod system all cut out today and it's ready to install.  I'm going to wait till I have a better idea of where things are going before I glue anything though.  I'll take some photos of it tomorrow for evaluation.

I've been doing some research on what I want to do for the rotate.  Steve's original idea that I want to use is a geared motor at the end of the gun carriage with a spiked wheel that would spin the gun 360 degrees.  After looking through many websites, I think I found a motor that will work.  I'll be running this gun at 7.4 volts, so the motor will be spinning about half it's rated RPMs, I think.

Here is the motor. http://www.dx.com/p/high-torque-80rpm-12v-dc-geared-motor-91628?tc=USD&gclid=CjwKEAjwxtKeBRDMzoeQmYn5uHcSJACGCF3D5p5zz3sy2zZyJL-lgL8qzTj8MfNhtCW4q1FLSNQh3xoCsXzw_wcB#.U9bwumOTFIq

Do you guys think the motor will work for what I intend to use if for?

Also, will a 12v door lock actuator work ok on 7 volts? 

Thanks,

Caleb

 

[TyngTech]

That's a 4mm shaft motor.  I think that's a little light weight for the application.  I'd go with a 5 or 6mm shaft motors.

Possible options:

http://www.surpluscenter.com/Electric-Motors/DC-Gearmotors/DC-Gearmotors/140-RPM-3-6-VDC-GEARMOTOR-5-1795.axd

http://www.surpluscenter.com/Electric-Motors/DC-Gearmotors/DC-Gearmotors/180-RPM-24-VDC-INLINE-GEARMOTOR-5-1812.axd

http://www.sciplus.com/p/50-RPM-12VDC-GEAR-MOTOR_54785

http://www.surpluscenter.com/Electric-Motors/DC-Gearmotors/DC-Gearmotors/62-RPM-9-VDC-MERKLE-KORFF-GEARMOTOR-5-1685.axd

ST

[Caleb Smith]

Ok, thanks for the heads up.  The first option should work fine for me.  Going to order two today.

[Caleb Smith]

Ok, rotate motor was ordered, plus a ESC to control it. 

Took some photos of the elevate system for ya'll.  You can see the extension on the servo horn which is both crimped and glued.  You can also sort of see the piece I built that will go on the gun plate.  Last photo you can see where I'm planning on mounting the door lock actuator, plus the cardboard splinter shield which is built out of the box the gun was shipped in.  The cardboard splinter shield isn't permanent, I was just using it as a test to make sure my measurements were correct before I started cutting the wood.

[jvragu47]

Looks very well thought out Caleb. A suggestion. For the future,you  might want to replace the wooden linkage with either plastic or metal if you can.

[Caleb Smith]

Thanks for the suggestion. I guess that would make for a smoother and stronger elevate.  I'm using wood for the moment since it's the easiest thing for me to work with, but in the future it will probably get replaced.

[TyngTech]

A Bucky sphere carbon nano composite will be your best choice.  The lower mass will increase elevate acceleration resulting in faster target acquisition.

[jvragu47]

Fancy name for plastic. Eh, wot!  LOL.

[Caleb Smith]

LOL   Got an email this morning saying that the motors have shipped.  23 days till the battle, should get done in time.

I've attached a picture of the door lock actuator I have.  I was wondering if the two little knobs on top could be trimmed off?  It would make mounting it a whole lot easier.

Thanks, 

[Caleb Smith]

I think I forgot to attach the photo. LOL

[TyngTech]

No, they cannot be trimmed off.  Those are recesses for internal shafts.  I'm assuming you want to fit that side against a flat piece.  What you could do is ll a couple of corresponding holes in the flat piece for those knobs to fit into.

ST

On Thursday, July 31, 2014 7:54:25 AM UTC-4, Caleb Smith wrote:

[Caleb Smith]

I had wanted to put that side against the marker.  I'm pretty sure that the marker wouldn't like some holes drilled in it.  The reason I asked is because when the actuator is placed on the marker mount, those two knobs push the mounting holes on the actuator too close to the edge of the marker mount.

I found out the if I lift the actuator up a little though, those knobs fit in the crease between the two tubes of the marker's body. 

My plan for firing the gun is just a bicycle brake cable running from the nice trigger mechanism that Steve built looping around a piece of plywood to the actuator.  If you got that, great, if not I'll have a photo for you tomorrow. :)

Caleb

[Caleb Smith]

Sorry, no photo.  I still have to make the thing.  Things have been busy around here.  On the good side, the motors and speed controllers arrived yesterday.

The motors should have enough torque the wheel the gun around.  They also have plenty of speed which will be nice for tracking speedy Cromwells, but the ESC allows minute adjustment for long range gunnery.  I think I'm going to have some fun next battle. LOL

The ESC I'm using is one I found on Hobby King for brushed motors.  It's rated for 45amps, and is about $11 from the US warhouse.

LINK:  http://www.hobbyking.com/hobbyking/store/__32025__HobbyKing_X_Car_45A_Brushed_Car_ESC.html

So far it has worked really well, and it's very compact and easy to program.  I guess we'll see how well it works in the battlefield.

C

[Caleb Smith]

Finally, progress!  I've moved the actuator to a much simpler spot.  Plus I made the toothed wheel for the rotate. 

After my idea for firing the gun went up in smoke, I had to move the actuator.  The only place that would work was underneath the gun mount.  The arm of the actuator will be attached directly to the trigger thing-a-ma-bobby that Steve built. 

For the rotate, I was originally going to use a bicycle sprocket mounted on a motor at the end or the gun carriage.  After some close inspection, I decided that the sprocket wasn't going to work.  First, I think the sprocket is too skinny.  I think it doesn't have enough surface area and it would sink into the dirt.  Plus if I started the motor abruptly, the sprocket would probably turn into a mini ditch-witch.  Secondly, upon looking at a sprocket, it looks fairly complicated to mount it on a shaft.  So I've come up with the same idea, only better.

After gluing two pieces of 1/4" ply together and cutting out a circle with some teeth in it, I had my spiked wheel.  Kind of reminds me of a TTS drive sprocket.

Those ESC's are very compact, and may I say...tough.  Today I was playing around with one, running one of the rotate motors when smoke started to come out of it.  I quickly unplugged it from the battery.  I couldn't see anything the matter with it, so I hooked it back up to the battery, and it has worked fine every since. I'm not sure why it started to smoke, but I'm thinking it might have shorted out somewhere.

You can see how small these things are. 

  

Here is my failed attempt to make a device that would allow the actuator to pull the trigger.

Caleb

[jvragu47]

Great job Caleb. When I made the Pak40 anti tank gun I placed the actuator in a similar spot. It was the use of the salvage yard hatchback release on the Pak40 that moved many away from servo actuated firing mechanism.

So, since you'll be manning your artie piece, who will be taking movies?

John

[Caleb Smith]

Thanks!  Well, guess I won't be.  I think my two brothers will be coming again, but they might want to run some of the extra assets.  I've been trying to convince my sister to come down and take photos and video.  She's a little reluctant, but I think I might be convincing her.  I guess we'll see.
I fiberglassed the rotate wheel with FG cloth and TiteBond glue. Plus I applied a generous helping of glue to the teeth to waterproof and strengthen them.
If things go well, I might have this thing rotating today.

C

[Caleb Smith]

IT ROTATES!!!  Well, it did....   After a "quick throw it together to see if it'll work" moment, I was in the lawn testing the rotate.  It work alright.  There was some slippage, but I had the marker removed, so there was a lot less weight on the tail end which could account for that.  After only a little testing, the bearing for the shaft came out, (should really wait and install stuff before testing) which ended further testing.

If things go well tomorrow, I might have a video of it rotating, but no promises.

Wow, it's 11 Oclock, I need to get to bed.

C

[Caleb Smith]

Did some further testing today, plus took some video which will be posted tomorrow.    I mounted the marker this time unlike last night. 

Rotate was smooth, fast or slow, and slightly noisy.  Had some slippage in the thicker grass.  Might need to bring some scissors to the battle for clearing a firing position.

[Caleb Smith]

Video of the rotate.  https://www.youtube.com/watch?v=BvtTVZMvKlw&feature=youtu.be

[TyngTech]

WOW, it really works!   ;-)

Great work so far.

Steve

[Caleb Smith]

Thanks!  Since the video, I've upgraded to a larger wheel in hope of having less trouble in the thick grass.  Bigger wheel helps a little, but it still gets bogged down in the thicker grass.  Hoping to get the elevate and firing working by the end of the week.  That will leave less than two weeks to work out any problems. 

Caleb 

[TyngTech]

Caleb,

To make rotating easier, make a turntable for the wheels to ride on like they did with the real thing.  Don't forget that little frame underneath attaching to the center of the turntable that keeps the axle centered and the wheels on the table.

Steve

[jvragu47]

On Monday, August 11, 2014 9:38:05 AM UTC-4, Caleb Smith wrote:

Video of the rotate.  https://www.youtube.com/watch?v=BvtTVZMvKlw&feature=youtu.be

Excellent work Caleb. 12 more working days until  the battle. I'm sure you'll be done with time to spare.

John P.

[Caleb Smith]

Why didn't I see that before!  Looks simple enough to make.  That little frame might be a little more difficult to make.  Might have to brake out the welder...

Thanks, John!  I'm pretty sure I'll be done too.  I'm soon going to go out to the shop and work on building a bracket to hold the elevate servo.

[jvragu47]

On Monday, August 11, 2014 7:00:27 PM UTC-4, Caleb Smith wrote:

Why didn't I see that before!  Looks simple enough to make.  That little frame might be a little more difficult to make.  Might have to brake out the welder...

Or, for now how about this. Large piece of plywood base and then maybe a 1/2" thick plywood  circle  in the center for the tires to roll around. No welding required.

John P

[Caleb Smith]

Do you think the wheels will keep centered on the base without the piece that goes from the gun frame to the turntable?  That was the piece I originally thought I was going to need the welder for.

[jvragu47]

Just looks like a simple v attachment.  Attach the open end of the v to the gun carriage. Then, drill a hole in each end for the center of the turntable. Just need a bolt and a bushing then.. No welding required at then.

[jvragu47]

Forgot, just need two flat pieces of metal.

[Caleb Smith]

Sounds good, John!   

Just uploaded a video of me doing a complete overview 25 pounder's systems.  https://www.youtube.com/watch?v=qZoWHkV9pEc

Oh, forgot to mention, If your last name ends in "Tyng", ignore that statement about Cromwell tanks. ;)

[jvragu47]

Looks nice. Where is the CO2 bottle going to sit?

[Derek Engelhaupt]

It was underneath attached to the gun...

Derek

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[Will Montgomery]

Caleb,

You need more down angle and less up. The ground we battle on is not very flat.

Will

[Caleb Smith]

Ok, thanks, Will.  I adjusted the linkage this morning, and I've attached some photos of the new angles.

Yes, Derek is correct, it screws into the bottom of the marker. 

[Caleb Smith]

Got all the wiring done just a little while ago.  I'm excited to announce that the 25 pounder rotates, elevates, and fires all by radio control! How far along do I have to be to get designated?

All that's left it to build and mount the splinter shield, and build the turntable.  One week of building left, better get done quickly so I have time to practice.

[Will Montgomery]

Looks good.
Will

[Caleb Smith]

Thanks, Will!   Today I'm working on cleaning up the wiring.  It's amazing how many wires it takes to run a RC model...   

I'm going to be cutting the splinter shield soon, and was wondering what would be the better choice for wood.  I have some 4 ply 1/8" plywood, and some cheap 3 ply 1/4" plywood.

I was thinking the 1/8" would be Ok as I was planning on fiberglassing it with FG cloth and TiteBond, but what do you guys think?

[Caleb Smith]

Went ahead and cut the splinter shield out of the 1/8" ply.  It looks really good IMO.

I didn't go hog wild with detail, but I still think it looks pretty good.   I'll see if I can get it mounted tonight, then tomorrow I can work on the turntable.

[neroc1]

Caleb, I have been watching your build with great interest and enjoyment. I say well done to you, 

Neil "00funky" R 

[Caleb Smith]

Thanks a lot, Neil!

Got the turntable built yesterday morning, and built the V attachment last night.  I still have to attach the V to the gun carriage, but last night I just clamped it onto the gun for some testing.  Rotate is so sweet.  I'll have to post a video after the battle.  All that's left is to mount the splinter shield, which will be done this morning.

On Wednesday, August 20, 2014 6:11:17 AM UTC-4, neroc1 wrote:

[Caleb Smith]

Quick took some photos of the turntable and the V attachment.

The gun on the turntable.  The bottom circle is made a 1/4" ply with a smaller 3/4" circle on top.  Plus you can see the angled mounts for the splinter shield.

I connected the two circles with a bolt, which also holds the V attachment onto the base. 

Then the open part of the V is attached to the gun base via two screws.

Enjoy, and for those coming to the battle, see you in a few days. :D

Caleb

[Caleb Smith]

Almost ready to hunt tanks!!!!!!!!!!

[TyngTech]

Looking wicked Caleb.  Looks like I picked the right person to finish her up!

Steve

On Sunday, July 27, 2014 8:43:11 PM UTC-4, Caleb Smith wrote:

I'm in on this hobby too!  After Tyng Industries offered a half built artillery piece for a very reasonable price, I just couldn't refuse.  So, now I'm the proud owner of a half built 25 pounder that needs rotate and elevate.  I would like to get this ready for the next battle, so I'll be hurrying along. 

In the last two days, I think I've figured out the elevate system.  Basically, it's just a standard servo with an extension on the horn with a piece of wire running from the horn to the gun platform.  The servo has plenty of movement to get to the 10 degrees maximum elevation, plus plenty of down angle.

I've attached a photo showing the basic idea.  If you guys think it will work, I'll replace the wire with a wooden pushrod system.

Thanks,

Caleb

[Caleb Smith]

Thanks, Steve! I'm looking forward to getting to shoot some tanks on Sunday. 

I know this might sound a little silly, but how do you guys like to measure the 10 degrees maximum elevation?  What tools and procedures do you use?
Thanks,

C

[Frank Pittelli]

Not a silly question at all. We actually allow the operator themselves
to ensure that the maximum elevation is not exceeded. The procedure is
as follows:

1) Place the asset on level ground

2) Adjust the marker elevation to the maximum possible

3) Stand exactly 11 ft 4 inches in front of the gun, with you legs
spread apart.

4) Fire the marker

If you're afraid to fire the marker or you scream in pain, the elevation
limit has been exceeded.

Frank "Trigonometry Is Your Friend" Pittelli

[Caleb Smith]

Ok, heading out to the lawn to try it.

Thanks,

C

[Caleb Smith]

The 25 Pounder participated in its first battle on the 24th.  I was quite pleased that it went the whole day without a breakdown or failure.  Really, the only problem that I experienced was a little trouble with the Co2.   After firing a couple shots to make sure everything was working properly prior to the battle, I moved the 25 Pounder out into the compound.  Shortly after war was commenced, I tried to fire a shot at an incoming tank.  The gun didn't fire, the bolt just went forward.  Thinking that I was out of Co2, I unscrewed the bottle from the gun.  After realizing that the bottle was still full, I screwed it back on and the gun worked perfectly.  I'm thinking the bottle must have unscrewed enough that the pin wasn't depressed enough to let the Co2 out.

After that, I didn't have any trouble the rest of the day.  Thanks to Frank, I was right in the thick of the action.  I was placed right across from the bridge that the Repo Men had to cross to get the gold.  The only problem with that spot was that there wasn't a good place to hide my soldiers.  That explains why there was such a high amount of hit's taken during the first two battles.

The last battle allowed me to get more hits than I took.  Mostly because I had my soldiers in spots that if a tanker wanted to kill them, they had to show me the side of their tank.  Even in these good spots though, I still got killed four times. But, I got back at the enemy, making a total of 15 hits on various tanks. 

For those that have been waiting for the video of the rotate, I'll soon have that up.

Caleb