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Starting my 25 Pdr... Mirbat Gun.

All topics related to Armortek's 25 Pdr
Robert Reid
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Starting my 25 Pdr... Mirbat Gun.

Post by Robert Reid » Sat Jul 06, 2019 10:51 pm

So last weekend, I started my 25 pounder that will go with the Limber I did in an earlier thread. I am trying to do it up as 'the Mirbat Gun' but will likely do it in field colors, not in its current guise as a trophy piece.

Up to this point, nothing especially different or difficult in the built, including adding Dave Dibb's brilliant Armorpax bits. One variation from standard is the thin brass plate on the tail plate since trying to line everything up required me to cut the Armortek plate into two and then making a filler piece. I added a few rivets to make it all kind of disappear into the final paint job.

I also made the lever supplied by Armorpax "swing" by adding a pivot bolt. It's a small thing, but fun!

The real modifications will come in the weeks ahead. Right now, just starting to get the carriage moving forward. So far, despite a boatload of rivets, this is actually easier than the limber! But I suspect that will change.

Taking a lot of inspiration from several amazing builds including Jeff and Marcus! And while I was going to make this one blank-firing, I think I am going to save that for the 17 PDR. This one may well get sent back to the UK when finished, so I don't want anything that will make HM customs crap a litter of lizards... pardon my French.

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A small modification to Dave's lever... yes, it has a flat back. If you don't modify it! And swings very nicely with some drilling!


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Rear part of the trail showing my small brass insert piece. I must have made a mistake in the alignment as I just could not 'quite' to get the rivet holes to align. So I cut the Armortek plate in two and made a tiny filet out of brass and added some rivets. Historically accurate... well, it will disappear into the paintwork...

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Overall view. Lots of bits here and there as the modifications come together. Note some resin bits sticking up awaiting brass strips, rivet holes not filled, etc. Lots of work in progress right now.

The real work is going to start with the gun and recoil mechanism! But so far having a great time with the trail/carriage and, as always, Dave Dibb's parts are a great addition!

Cheers,

RPR

Marcus Kwa
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Marcus Kwa » Sun Jul 07, 2019 9:59 am

Seeing you starting your build makes me want to build another one........ Have a second 25pdr waiting to be converted into a 17/25 pdr......
I really love this 'little' kit, watching with interest!!!!!

Marcus

Robert Reid
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Robert Reid » Sun Jul 07, 2019 2:22 pm

I have a 17 pdr, too. It has been very tempting to build a Pheasant. May have to do that eventually. I collect 'live' (aka full-sized firing) antique artillery and so love these amazing models!

Your build is definitely inspirational! I just ordered 1,000 small head rivets, too!

Cheers,

RPR

Marcus Kwa
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Marcus Kwa » Wed Jul 10, 2019 12:36 pm

Would love to have one of those 1/1 civil war cannons! Do those also come in a smaller scale (1/6 or 1/10) and kit form?
1000 rivets should be enough! I find them everywhere in my house, so some spares are definitely needed!

Marcus

Robert Reid
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Robert Reid » Sat Jul 13, 2019 1:00 pm

HI Marcus:

Thanks for the kind note!

Restoring live artillery is the hobby that modeling goes along with! And it's really the same skill set, only the tools and forces involved are larger. And I'd argue that making a 1/6th scale 25 pounder is a heck of a lot harder than a 1:1 Napoleon! Except for the tonnage.

There are a number of good quality cannon kits in all sizes. Or you can buy a barrel and build your own cannon essentially from scratch. The wheels are the tough part. But with your skills, you would knock them right out! Of course, you could also do a 'late civil War/Victorian cannon' on an iron carriage, which is all about riveting and soldering and welding!

I'll post some pictures of one I am almost finished... an Armstrong 6pdr RML from the Punjab. It's an all iron/steel carriage and would make an amazing 1/6th scale and could be done 'from scratch.' In fact, off to reassemble the wheels and fit the hubs in a moment!

Not sure if you are in a part of the world where 'live' fire is allowed. But there are many barrels you can buy pre-made from golf-ball size down to .50 cal. that when built safely will fire a ball with black powder. CVA used to make beautiful kits and they are not expensive. And as they come lacking a lot of detail, there is a lot of room to go much further than the manufacturer! Here is a 'restorable' one on ebay cheap! But keep in mind that these are a big no-no in the UK as they are considered firearms. But they made a naval cannon and a napoleon that I would estimate are 1/12 scale. To do 1/6th scale, you are probably wanting to find a barrel that is at least 16" long and go from there. Naval carriages are by far the easiest to start with. But so are iron carriages for a modeler with your metalworking skills.

https://www.ebay.com/itm/Vintage-CVA-Di ... SwiRldF7jw

Or you can go all-out and simply buy a full-size barrel from these guys (they are the varsity) and build from there. It's not hard!

http://steencannons.com/cannons/

This is probably a 'winter carriage' which is used for storage, not battle. And kept the wood carriages out of the elements. Note lack of trunnion caps?

https://www.flickr.com/photos/sarge_schultz/3710567822

But those carriages could be easily replicated with a mill and riveting/soldering skills!

Glad to chat cannons with you any time! And I definitely take inspiration from your Armortek modeling work!

Cheers,

RPR

Robert Reid
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Robert Reid » Sun Jul 14, 2019 9:11 pm

HI Marcus:

Was doing a bit more looking... and these (from Traditions) are available in 1:6th scale! the 14.5" barrel would translate to roughly a 7 foot long Napoleon cannon

https://www.dixiegunworks.com/index/pag ... arge+Scale

Fully Firing. I'm going to be down there next month (at Dixie) and if you want me to take some detailed photos of one or look at it for you, I am glad to!

Cheers,

RPR

Marcus Kwa
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Marcus Kwa » Mon Jul 15, 2019 7:16 am

Thanks Robert!
That website of Steencannons is amazing!
My first large scale (non plastic) model was a naval 24pdr made by Rhodes limited in about 1/10 scale, say 15 years ago...... Wooden carriage and a glorious brass barrel! Bought it after a visit to the USS Constitution when I was working in the US.

Getting the stuff to Europe is the tricky part nowadays. Have my eyes set on a 6pdr model by Mini Cannon Tech but have not yet had the courage to order it....
https://www.minicannontech.com/store#!/ ... y=19957109

But I am hijacking your post! How is the 25pdr going?

Cheers,

Marcus

Robert Reid
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Robert Reid » Mon Jul 15, 2019 9:53 pm

Not hijacking at all! Artillery is artillery!

I didn't get anything done on the 25 pdr this weekend and won't get back to it before Mid-August. But I did almost finish the Armstrong. Just needs assembly.

Cheers,

RPR

Robert Reid
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Robert Reid » Sun Aug 18, 2019 10:43 pm

So after a long hiatus posting... not a long hiatus working... here's a few pictures from this weekend.

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This is the new breech (The bronze piece below). At the top of the picture is my scale 25 PDR shell, which is an all-brass 28-Ga shotshell... which is an almost perfect 1/6th scale 25 PDR. On left is the barrel, which has been opened up to .750 to take the new breech (which will also serve to align/hold the barrel onto the breech block). On the right is the modified breech block.

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This is the Armortek Breech block undergoing its first modification... which opens up the bore to .750 to take the above bronze breech tube. Four jaw chuck lets me turn an odd-shape object perfectly.

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Here is the block being turned in the 4-jaw chuck.

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This is the finished breech block and the breech tube, waiting for deburring and for the recess to be cut to take the 'shell' so that the breech itself will close over it. Need to do some final measuring. Barrel slips on and will be final attached and pinned. This is not going to be a firing replica (blanks that is) though tempting. I think it's going to end up in a place where shootable things are frowned upon. More on that as things progress.

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With everything machined and ready to go together. Now on to some other stuff....

After looking at a couple of other builds, this gun definitely needed a recoil mechanism. And so I built one up. Not happy with it yet as the springs I had on hand are all wrong... But once I get some new springs it will work just fine.

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Overall, the design is somewhat stolen from Jeff's build, but with a few modifications. It's not a very intuitive thing to engineer. When I finally get springs in and get it working, I'll post a diagram for anyone who wants to emulate. It's not hard. It just takes some thinking.

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Here is a close-up which may help decipher things... or not. Like I said, the springs are all wrong. eBay, here I come!

Cheers,

RPR

More on this in a moment.... as I have to start a new thread for the rest of the photos.

Robert Reid
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Robert Reid » Sun Aug 18, 2019 11:00 pm

And after that short commercial break, we are back!

Another feature stolen from Jeff's build is the nuts holding on the front of the recoil mechanism. I didn't have the drive to create a whole bunch of eye bolts, so I just soldered blocks on and then radiused them and put some 'cuts' in them so that when they are painted, they will look like eye bolts. I cheated, sorry.

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Oh, I mentioned Radiusing the blocks... if you don't have a radius gauge set... they are well worth it!

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Knowing the radius, it's easy to pick a drill that will let you match your part to the piece. In the end, however, I just ended up roughing it in with a Dremel and soft-soldering it. And all is good. But didn't want to waste the photo. Radius gauges are helpful in so many places!

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So here are the blocks being made up in another incredibly useful tool... a 5c Square Collet (what kind of witchcraft is this????). To hold a piece of bar stock while I center drill it and tap it to hold the bolts that will hold on the nose of the recoil mechanism.

Once these blocks were made up, I threaded them to 8BA and threaded in some 8ba rod... which when nuts and washers are added will hold the front plate on fine, even under the 'pressure' of recoil (ie, me pressing on the barrel and letting it snap back).

Here are some pictures of the trail as I keep adding features to it. Still a lot of rivets to go (inside and out). Along with lots of small detail parts. But it's coming along well. The black etch primer is to stop some of the rust I was getting... humid shop, fingerprints and time... easy to remove. But on assembled parts, I just shot some black self-etch on. Note some details like braces made of pipe and, of course, ArmorPax great upgrade bits! Always a pleasure to add Dave's bits!

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Note added bits, but I am also putting rivets inside and outside the frame pieces. Since I abhor holes with nothing in them, and I think the rivets are supposed to be inside and out.

More to follow... Because the 'real' detail work is just beginning.

And going to have some interesting things to do with the axle backing plates and hubs, both to match the backing plates and to match the limber wheels, which, if folks remember, are removable with nuts and studs as original.

More to come in the weeks ahead! Loving this kit!

Cheers,

RPR

Jeffrey Goff
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Jeffrey Goff » Mon Aug 19, 2019 7:34 am

Looking good Robert, these 25 pounder kits are very satisfying to build with plenty of scope to embellish
Regards Jeff

Robert Reid
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Robert Reid » Sat Oct 26, 2019 10:15 pm

Got back to the 25 pdr for a day. Still a lot of farm work and a beautiful day. But needed a quiet day in the shop playing with Armortek. Soon enough, the snow will arrive and I'll have LOTS of time. But Just needed to tinker.

So I love this kit, but without a doubt, this is the most peripatetic build I've ever been involved with... I am helter skelter all over the place trying to get one thing done to fit to another and back again... because everything is such a system! And I had to go an build myself a recoil system which, to parahrase Doug Neidermeyer (Faber College '63) "involved more than two dozen individual acts of engineering perversion SO profound and disgusting that decorum prohibits listing them here..."

I am adding details as I go, but also thought I'd throw in some thoughts that would help with folks get the gun working like the finely-engineered artillery piece it is. And for those familiar with 'real' artillery, it is just wonderful that you can turn beautiful, oily handwheel and feel a ton of metal rotate with the balance and tolerances of a fine Swiss watch. An Armortek kit should (and can) do the same!). Just takes some care and attention to detail during assembly

But first... some updates. Almost 2 months ago, I got the breech finished up and put together barrel and breech. The breech was modified to take a brass 28 ga shotshell, which is an almost perfect scale replica of the 25 PDR casing. They have to be shortened, but they are right on and go perfectly with Dave Dibb's resin shells and shell carriers!

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Here is the breech, though I needed to to a tiny bit of machining to get the breech block sliding as smoothly as I wanted it. This was due to my new chamber lip being a tad taller than the factory one.

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This was an idea taken from Dave Dibb's build at Armorpax... the top of the breech is not a nice, smooth machined piece. More likely a large casting or forging. I would guess a casting. So I took a cue out of my Rolls-Royce engine build and used my plenishing hammer to roughen up the piece all over. I think Dave did it with a spray-on coating, but I decided to put it right in the metal. Note that before plenishing, I smoothed and softened up the edges and rounded things so it doesn't look so 'machined.'

And it's on to the recoil system. In an earlier posting, you could see my 'gen 1 attempt.' And it was worthless. Springs were either so strong that they snapped the barrel forward hard enough to break things (and made 'pushing the barrel back' almost impossible) or they were so weak that if you elevated the gun, the barrel would flaccidly sag backwards in its recoil channel. The answer was compound springs... with variable rates. In fact, I ended up using 12 springs, 4 of small diameter and relatively soft. 2 of small diameter and much stronger. And 6 larger diameter outer springs, all the same rate. On sliding guides fitted to a pair of brass rods. I don't even want to think about the time it took to get it right...

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The result far exceeded my expectations. And I'll try and post a video. But the barrel goes back smoothly about 1.5 inches. And then goes forward just like it's running on hydraulics. Smooth as silk! Shuts at the front just like it should and makes no noise or snap. I'll try and post a video of it tomorrow. Oh and because the actual barrel carrier on the original has rows of rivets on it... I added rivets. Hard to see in the above photo. But they are there. Soldered in and smoothed up on back.

And on the subject of 'smooth...' next came fitting up the barrel trunnions. As a restorer of 'real' artillery, I can tell you that this is one of the most critical parts of any piece. So when it came to assembling the trunnions, I opted to build around the actual trunnion piece and then make the rest of the carrier 'fit' the aligned cups and caps.

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The first thing was to true up the trunnions theselves. They were actually true from Armortek. But the cheeks had some material in them that was creating a tight fit on the gun carriage trunnions and caps. So set the whole thing up in the Monarch and trued up the edges, but without removing anything from the actual bearing surfaces. I actually debated replacing them with brass or bronze as 'aluminum on aluminum' is a rather tough choice for long-life smoothness. But decided that since we're not headed to El Alamein with this one... it won't get hard use!

Before machining the trunnions, I had assembled the cheek plates and the cross 'bar' (where the pivot bolt goes) and epoxied them together. I did this with the trunnion block tapped into place. It would not move, but it also aligned my 'top' trunnion cups perfectly while the bottom pieces were locked together with cap screws and epoxy.

Next, the trunnion caps were fitted (and stamped to mark them... always stamp them!) and then line-reamed.

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I was lucky enough to have a decimal reamer close enough to 10MM that I could ream them in a line and then lap in the actual trunnions in. Which worked out absolutely perfectly! They were 'almost' perfect and a few minutes with medium lapping compound left our top

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Here we have the assembly 'together' and being lapped. Lapping compound can is in the back. Took fewer than 5 minutes to get it moving completely smoothly with no binding or tight spots.

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Here we see the trunnion caps (with their stamps) in place and lapping compound squeezing out of the gap.

With the Trunnions now in perfect alignment, it was time for the 'base' to get some attention. Because as careful as the alignment process was at the trunnions, it still left the 'base' about 1/2mm out of alignment. Which means that when it goes on the trails, it will have big trouble turning smoothly. Everything has to be in perfect alignment in order to elevate and slew correctly and smoothly. So the whole unit was fixtured to the mill table and set up to take a skim cut off the bottom rails. A digital readout (DRO) makes this much easier!

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Here is the fixtured piece ready to take a cut.

And making a cut down the 'high' (technically low) arm to put it in alignment with the other side. About 1/2mm removed which does not seem like a lot but would have made the process of trying to get the barrel to slew really difficult. This is what I mean about going forward and backwards a lot with this kit! It's easy looking, but there is a lot of small stuff to make it really come out to its highest potential!

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That's about all I got done today... Or at least photographed. Lots of little bits of back and forth on axles, seat, armor-shield, etc. But all these bits are requiring some 'steps back' to re-evaluate. One of which is trying to 'squish' copper rivets and get them to dome. I thought my pneumatic brake riveter would handle it. Well... didn't even move the shank. So I annealed it. And... nothing. So off to get some aluminum rivets to use on the armor. And on the Rolls-Royce armored car. Because properly dollied rivets are... properly dollied!

Cheers,

RPR

P.S. Anyone got a line on 1/6th scale Broadarrow stamps? Because just about every part should have one! And I bet the Centurion folks would like to add some Broadarrows. Job for someone who has die- and stamp-making skills???? Because I surely would love one!

Marcus Kwa
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Marcus Kwa » Sun Oct 27, 2019 9:50 am

Excellent post Robert!
Just having a machine shop like yours...............
I have rebuild and modified (upgraded?) most of the parts 3 times over, as there is always someone who has a great idea that just needs to be implemented on my gun too. I just cannot resist it....... :roll: And luckily my work space is underground and soundproof as not to scare my neighbours in whatever way......
Love to see how you built your recoil system, as the impact of my current system also does damage the detail parts attached to the gun slide (even when brazed together).

Cheers,

Marcus

Robert Reid
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Robert Reid » Sun Oct 27, 2019 2:14 pm

HI Marcus:

That is high-praise coming from you! Thanks very much.

I will do a short video of the recoil mechanism. Not sure how it will work with the linkages. I'l have to do them with as little 'drag' as possible! But dooable!.

The main thing was a LOT of springs and potential spring travel and mixing and matching springs. I'll see if I can post some more details off my pictures (circles and arrows!) and some descriptions. The key was full-length rods. A 'fixed' plate that is mounted to the stamped steel guide rail with a couple of 5BA screws. And then simply tinkering with springs. You can see the aluminum guides in my picture. Those slide along the brass guide rods.

More coming!

Cheers,

RPR

Robert Reid
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Re: Starting my 25 Pdr... Mirbat Gun.

Post by Robert Reid » Sun Oct 27, 2019 10:26 pm

Hi Marcus:

Here is a short video I shot this morning showing the recoil mechanism working. It's actually running a bit slow this morning because my workshop was about 50 degrees... and I think the grease had congealed a bit on the rails!

https://www.youtube.com/watch?v=xRUe-5P8ydE

But you can see how it moves very much like it is returning on hydraulics.

Here are a couple more build pictures from today.

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Here is the barrel assembly showing rivets. Lots more to do on it... detailing, linkages, etc. But the 'hard' part is done. Or so I think it is. Maybe.

Any upcoming project. Here is an original Clinometer. I'll be making a miniature in brass. Won't turn, sorry. But will be the right size. Which is a bit under an inch long. Hey Dave Dibb... if I make a spare, would you like to borrow it to cast up some extras? I assume I will need two as there will be a 17 pounder coming up sooner or later.

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On the subject of amazing things that people make....

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This is a really tough little guy to install! But with some good twisting and rolling and cyanoacrylate, the cone slips on. Be really careful NOT to kink it. And just work it until it conforms. You can't just wrap it up. It has to be a 'freestanding' cone the same dimensions as the aluminum cone if it's going to sit and glue well. I used the handle of an X-Acto knife which was perfect.

This is going to be interesting, though...

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This is the sector gear for elevation and it looks like it was laser cut and like the laser was getting a bit hot on the insides of the teeth. I am debating whether to recut, make new or just dress and bet that it will probably work ok. Anyone else have one like this? Did it cause any issues? In an update, got a nice note from the Armortek Mothership -- great that they follow our builds so closely!!! -- and said that the part should not look like this and there must have been some problem with the cutter. They are dispatching a replacement. How awesome is that!!!!)

As I did with the limber, I am converting the hubs to studs and nuts, rather than bolts. These are 5BA bolts that will get cut off and tuened into studs and they will take the 5BA brass hex nuts.

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Last, but not least... lots of different stool interpretations done on builds here. I had a bit of fun and used a piece of Lignum vitae that was floating around the shop to make the seat. Turned the aluminum seat off the post, leaving just a flange. And fit this up with epoxy. Looks nice. The chunk of Lignum Vitae that I have used to be part of the turbine Bearings at Niagara Falls Power plant. So a bit of history in the seat.

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I'll be picking this up again next couple of weeks. Maybe even next weekend. Depends on the weather and what's going on here at the farm.

Cheers,

RPR


Cheers,

RPR

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