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Mk1 gun carrier scratchbuild


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I decided to follow the video implicitly and used hair lacquer to adhere the rivets because, it was suggested, it would leave minimal residue. It would seem to be the case, however I haven't done enough rivetting to know how well the hair laquers adhesive qualities stand up to the test of time.

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3 hours ago, Model Mate said:

I’m going to refrain from riveting the inside

 

Wise choice I think for the reasons you state otherwise the gun carrier is looking better and more complete with every new post.

 

Pin vises are very handy to have. At my last count I think I have at least half a dozen on the work bench and a couple more in a tool box and they all get used regularly. Not only useful for holding pins and drills for drilling but also for holding wee tiny parts while you cut, drill, or file on them and not just round parts but flat parts like photo etch, and bits of tiny wire so that you can twist them up nicely into a nice bit of cable - pin vise, not just for drilling holes; remember that vise is in the name ;)

 

As to using CA for attaching your nail caviar / rivets - at the moment I have been using CA almost exclusively for this and yes it can be a bit messy and can leave a bit of extra around the edge.  I use a medium viscosity CA as I find it easier to handle and prefer it's longer setting time. I have been using a plastic dental pick toothpick thingy to apply the CA - I scrape the pointy end to sharper tip and a wee drop of CA will stay on the end which I can place where I want. I find the CA doesn't set and build up on the tip like I found it did on a metal pin.

 

After the CA has set, I then use a cotton bud wetted with a bit of CA debonder and gently go over the rivets ( or other CA attached part ) to remove the excess CA spillover. 

 

cheers, Graham

 

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good advice, thanks Graham. I've heard of others using acetone to remove excess superglue, which sounds like a reasonable idea. I've just left it - it doesn't seem to be too much of a build-up as I'm using thin glue. Hopefully it'll disappear under a coat of primer.

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8 minutes ago, Model Mate said:

I've heard of others using acetone to remove excess superglue

 

I tried acetone and it does work but I found it was more aggressive in softening the plastic. The product I have been using is Golden West (brand) Super Solvent (product name) and according to it's safety data sheet is mostly Nitromethane cas. no. 75-52-5

 

Not as aggressive a solvent as acetone with respect to styrene but is a pretty effective paint stripper.  Common drug store nail polish remover ( there are two kinds, acetone based and acetone free ) may be a bit less aggressive than hardware store acetone but I have never tried them. 

 

cheers, Graham

 

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Finally got the rivets completed on the upper hull, so time for primer – hurrah!

 

Unfortunately my experiment with superglue in lieu of TET was a bit of a fail – numerous splodges and clumps around the rivets – grrr. It’s not great, but I think I’ll have to live with it – I just can’t face tearing them all off and redoing them. A bit of paint, wear and tear and assorted muck and dust and hopefully they won’t be too obvious. Lesson learned though…..

 

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At least the inside looks ok – no rivets!

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19 hours ago, vytautas said:

Looks very good. It seems to me that small inaccuracies are good, they enliven the model and make it more interesting, and this matters.

 

Vytautas

Oh well. In that case I guess you will find all my models very ‘lively’. 😀

 

FWIW I do agree that an imperfect model often shows a bit more ‘spirted’ approach to modelling than does a picture-perfect replica.

 

It’s evidence that the modeller was pushing his / her own limits.

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  • 3 weeks later...

Life’s been a bit of a struggle just recently – I finally caught COVID (always late to the party) and it’s triggered off a bout of chronic insomnia. Now that might sound handy for a time consuming hobby, but I’m so tired I really can’t concentrate, so it’s been of no benefit at all.

 

Still, I tried a few bits, returning to the challenge of the wheels. I’d already carved and moulded (milliput in a blue stuff mould) a copy of a single spoke, but they really weren’t good enough. I had another go at making a few masters using 2mm plastic tube with flattened collars of slightly wider tube at the ends to get the fluted shape. I decided to give up on the idea of making them oval in cross-section, and resigned myself to the simple circular section of the 2mm tube for the central portion at least.

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After fettling the ends a little, I fixed them, along with the shell masters I made up ages ago, onto a piece of polystyrene foam board and made up a mould master. The results were less than spectacular – I just can’t find a way of avoiding bubbles, and the hit rate is extremely low. I’m lucky to get a single decent piece on each try. I attempted altering the resin mix, using 40/60 and 30/70 A/B as opposed to 50/50, but it really made no difference other than slightly more rubbery parts while they cured.

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I took another approach to the mould, and tried laying the parts flat.

52221337882_5b8a028184_k.jpg

 

The spokes are a little more successful with this mould after a bit pf cleanup, but the bunch of shells all together is still pretty awful.

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I guess I need a vacuum chamber, but I’m not going to be able to tackle that right now.

 

As I’d already deviated from the spoke shape, I thought I’d simplify them further and do away with the fluted ends, using plain 2mm tube.

I drilled the hub holes in 10mm tube, using a paper strip template I’d knocked up on CAD a while ago to space the them reasonably accurately.

52222833160_678cc08f6d_k.jpg

 

I cut the hubs from this, glued in some plastic rod to each hole and dug out my wheel jig. I’d printed a circular “target” to assist with alignment and I fixed this into the jig.

52222343466_e60ee1ef1c_k.jpg

 

Dry-fitting the 2mm tube onto the hub revealed that the fluted spokes would never have fitted anyway and I think they’ll look ok, particularly as the secondary, outer rim of these wheels will drop them into shadow pretty well anyway.

52222832600_f244cf3046_k.jpg

 

All I need now is to find a 2mm drill bit to carefully enlarge the holes in the rim and I’ll be able to make up at least one wheel. I’ll need more tube for the second, but let’s see how the first goes.

 

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I see you are still struggling with the wheels for the artillery piece. Wheels look so easy but in reality can be anything but.

 

I have spent the last couple of weeks playing around with ideas on how to make the wheels for my Isotta-Fraschini armoured car. Many diversions away from making artillery style spoked wheels but every little side adventure brings with it goods ideas. In fact I am much closer to having something acceptable for the wheels of my Poplavko Jeffery armoured car build and yet another side project of the same sort. Much time has been spent delving into the intricacies of paper card modeling techniques which after all where the source of inspiration of this build, a few more of your builds, and numerous builds of my own. I have cut hundreds of small and largish circles and rings from heavy weight cardstock, mixed-media and watercolour artists paper, plastic card, and brass plus many, many other bits and pieces.  I have also been exploring the possibilities of using jewellers carving wax as a prototyping material - I think it has lots of possibilities not only for prototyping a master from which to make a mold but it could also be used to make a finished piece.  Wax you ask?  Yes indeed - it's not the common soft bee's wax or paraffin wax your gran probably used when canning jam. Jewellers carving wax is much harder and easy enough to cut, grind, drill, sand, and machine. 

 

I had to go looking for some pictures of the Gun Carrier MK.I and the BL 6inch 26cwt Howitzer just so I could get a good look at the wheels. There does seem to be some variety in the wheels used on these artillery pieces. Going down the path you are heading seems to be a good compromise especially on a model of this size. I am sure it will look the part once completed.

 

You may have already found this good reference or the BL 6 inch 26cwt howitzer but just in case you have not:

 

https://viewer.slv.vic.gov.au/?entity=IE5329457&mode=browse    ( view online or down as PDF )

 

The State Library in Victoria (Australia) has quite a few very interesting historical documents that can be viewed online or downloaded as PDFs. On pages 102 and 103 of the linked to document you will find a couple of very nice period photographs of this artillery piece providing a very nice view of the shape of the spokes. As already noted, I did find some variety in the wheels of these period artillery pieces some of which where much more rounded and oval shaped than what I see in this document.

 

Bubbles when casting - always a challenge. Some time ago I started to use a cheap syringe with a blunt tip dispensing needle for "injecting" resin into molds.  Also works well for dispensing resin into simple open face molds as well. Since I have starting using this technique I get near zero bubbles. 

 

For small bits I use a 5mL syringe with a 14g ( green ) blunt tip dispensing needle, suck up the mixed resin, invert syringe and gently expel any excess air from the syringe ( use a paper towel ) and then inject the resin in the mold by gently inserting the needle deep into the mold and slowly dispensing the resin working your way back out of the mold leaving a generous overpour on top ( easier to clean up a bit extra that trying to file holes ).  I get the syringes and dispensing tips in bulk from Amazon. There are two types of dispensing tips - those with a metal ( usually stainless steel ) tip and those that are a tapered plastic tip. I prefer the tapered plastic tip but the metal ones have their other uses too. My preference is for a 14g tip but a bit smaller or larger would be OK too.

 

The syringes can be reused. I typically get at least a half dozen uses from each one, sometimes a few more.  After dispensing the resin into the mold I dispense any extra and then use methyl alcohol to clean the tip and syringe and then wipe with a paper towel. 

 

p?i=5ec723613647aaf15047bbda6390447e

 

cheers, Graham

 

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Despite little time and even less mojo, I finally got a 2mm drill bit and grasped the wheel nettle.

 

I drilled out the perimeter holes in the wheel rim, discovering in the process that 2mm wasn’t quite enough, so each one needed reaming out with a combination of scalpel and needle file to get the tubes to slide tightly through. The whole thing was placed into the jig using my dartboard template and I pushed each of the tubes onto the hub rods.

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A slosh of TET and everything was fixed in place. I cut off the protruding tubes and wrapped a thin strip of 0.2mm plastic card around the rim as the “tyre”. The face of the main wheel isn’t brilliant and could do with filling, but then the outer wheel extension mostly covers it all anyway, so no problem.

52242165338_04b30e219f_k.jpg

 

It’s not perfect, and as the spokes are just round tubes, not particularly accurate, but it’ll do for me – at least it’s round and reasonably regular. Once my delivery of fresh 2mm(ish) tube arrives, I’ll finish off the second one, fix them all together and add the rest of the detail – hubs and perimeter rivets/bolts. As per the Colonel’s suggestion, I’ve also got a box of syringes and tips on order, so I did consider casting and copying this one wheel, but to be honest, it’s probably more work than completing the second as I’ve already done for the first; I have the rims and hub ready to go anyway.

 

After that, it’ll be back to the rivets – hurrah!

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The first wheel has moved on – wheels keep turning!

 

My attention turned to the outer wheel rim. I think these were added to help spread the load of the gun on soft, muddy ground and appear to have simply been bolted onto the spoke fixings of the inner wheel. As a result, there is a series of recessed bolt heads on the face of the extra wheel.

 

I started these by marking them out with a pin based again on my dartboard template, and then drilled 1.0mm holes part way through the rim. My original idea was to drop in 0.9mm nail caviar balls to represent the recessed bolt heads, but drilling the holes a consistent depth just didn’t work and the balls either stood proud or sank out of sight.

 

I tried poking in lengths of 0.8mm hex rod, with the intention of trimming them to the face of the wheel, but again, this wasn’t easy or effective. It was hard to centre the rods in the larger holes and they still wouldn’t be recessed.

52245184700_555fb37092_k.jpg

 

In the end, I drilled all the way through the rim with a 0.9mm drill and poked the hex rod in from the back, pushing them slightly into the recesses while the glue dried and trimmed the backs off once it had all set.

52244978839_f20c3a67a1_k.jpg

 

I made up the hub faces using circles of 0.5mm card and again used the dartboard to mark out the rivet positions. A slice of tube for the centre and flanges using tiny triangles of 0.5mm card were glued in place together with 0.9mm nail caviar rivets.

52244978659_777acf585e_k.jpg

 

Finally it all got glued together and received a squirt of primer. I’m reasonably happy with this at last – just need to get the other one done and then they're ready for paint - it'll be the funky camo pattern that the rest of the gun is painted in.

52244704463_63d90b37d2_k.jpg

 

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3 hours ago, Model Mate said:

In the end, I drilled all the way through the rim with a 0.9mm drill and poked the hex rod in from the back, pushing them slightly into the recesses while the glue dried and trimmed the backs off once it had all set.

 

That is a very creative solution for adding the recessed bolt heads and the result looks quite nice. I have made a note.  Beats drilling a large shallow hole and trying to drop in a bit of smaller hex rod and getting it all centered up to represent the bolt head.

 

The wheel is coming together very nicely and looking the part.

 

cheers, Graham

 

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If you have problem with big air bubbles in casts, they appear when air is trapped during pouring, you have to find a way to let air go. You have pour slower, you can use syringe, or what I found works quite nice, use small rod submerged in resin and pour one drop at a time.

Resin despite low viscosity likes to trap bubbles and you have to remove them forcefully for this you can cut mould a little in places where bubbles are appearing and use small rod to stir them.

 

Edited by Kalor
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On 7/29/2022 at 5:25 PM, Kalor said:

If you have problem with big air bubbles in casts, they appear when air is trapped during pouring, you have to find a way to let air go. You have pour slower, you can use syringe, or what I found works quite nice, use small rod submerged in resin and pour one drop at a time.

Resin despite low viscosity likes to trap bubbles and you have to remove them forcefully for this you can cut mould a little in places where bubbles are appearing and use small rod to stir them.

 

Hi Kalor, Another way to avoid bubbles in the rubber assuming you don't have a vacuum machine/pump, is to use a cheap hog hair artists paintbrush and apply a thin coat of rubber to the mould. This negates bubbles on the detailed surface.

The resin is a separate problem that was always a challenge to me!

 

Colin

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You can try using talc powder (although it's getting trickier to find) in the mold as well- dust it into the mold surfaces and remove any excess. It helps resin flow in the mold- of course trapped air can still be a problem. If you can, make your molds such that the gate fits the nozzle of a large syringe snugly, and flows from the bottom- pushing resin up into the mold cavity. Air vents at the top of the mold cavity allow the cavities to fill from the bottom up... having to accommodate injection methods is a pain, but, in my experience, worth the effort.  

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This is all really helpful advice, thanks folks. I’m not having little surface bubble problems, rather large bubbles that leave the parts  split in half. I’ve drilled holes in the ends of the mould to try to act as an air-escape route, but of course in the soft rubber, they just close up and don’t do anything. My syringes are on order, so hopefully they’ll improve matters.

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On 27/07/2022 at 13:28, Model Mate said:

The first wheel has moved on – wheels keep turning!

 

My attention turned to the outer wheel rim. I think these were added to help spread the load of the gun on soft, muddy ground and appear to have simply been bolted onto the spoke fixings of the inner wheel. As a result, there is a series of recessed bolt heads on the face of the extra wheel.

 

I started these by marking them out with a pin based again on my dartboard template, and then drilled 1.0mm holes part way through the rim. My original idea was to drop in 0.9mm nail caviar balls to represent the recessed bolt heads, but drilling the holes a consistent depth just didn’t work and the balls either stood proud or sank out of sight.

 

I tried poking in lengths of 0.8mm hex rod, with the intention of trimming them to the face of the wheel, but again, this wasn’t easy or effective. It was hard to centre the rods in the larger holes and they still wouldn’t be recessed.

52245184700_555fb37092_k.jpg

 

In the end, I drilled all the way through the rim with a 0.9mm drill and poked the hex rod in from the back, pushing them slightly into the recesses while the glue dried and trimmed the backs off once it had all set.

52244978839_f20c3a67a1_k.jpg

 

I made up the hub faces using circles of 0.5mm card and again used the dartboard to mark out the rivet positions. A slice of tube for the centre and flanges using tiny triangles of 0.5mm card were glued in place together with 0.9mm nail caviar rivets.

52244978659_777acf585e_k.jpg

 

Finally it all got glued together and received a squirt of primer. I’m reasonably happy with this at last – just need to get the other one done and then they're ready for paint - it'll be the funky camo pattern that the rest of the gun is painted in.

52244704463_63d90b37d2_k.jpg

 

What can I say?
Whenever I look at your model and the work behind it, I hold my breath...

Respect!

MD

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7 hours ago, THEscaleSHOW said:

What can I say?
Whenever I look at your model and the work behind it, I hold my breath...

Respect!

MD

Thanks MD, with the quality of what you’re turning out at the moment that really means a lot!

I’ve finally rescued my big bottle of Tamiya glue (aka airbrush cleaner) so hopefully I’ll find time for a session to get cracking once more, it’s been so slow for me recently.

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My order of 2mm tube arrived, and with it a smidgeon of enthusiasm, so I got cracking with the second wheel. The outer rim had a bit of a gap in its outermost ring, so I filled it with a scrap of 0.5mm card and cut it flush. My order of 2mm tube arrived, and with it a smidgeon of enthusiasm, so I got cracking with the second wheel. The outer rim had a bit of a gap in its outermost ring, so I filled it with a scrap of 0.5mm card and cut it flush.

52291674056_a1e21c85e1_k.jpg

 

The first wheel needed a “tyre” adding so I scraped back a bit of primer and stuck on a curved strip.

52291677763_40ac4cb40a_k.jpg

 

And here they both are after a fresh coat of primer – the new 2mm tube is clearly a bit narrower than the first batch, and the hub detail is a bit vague – I think my new nail caviar is actually also a bit smaller than the originals, but as the wheels will be on opposite sides of the vehicle, I don’t think it’ll be noticeable. The photo makes them look very different, but they look pretty similar in real life.

52291677823_97895599d2_k.jpg

 

I also got a few more rivets on the lower hull (interior ones for the most part), but there’s not much to see yet – lots more to go before it’s worth putting up a photo.

 

The last little addition was the exhaust pipes on the engine. They were cut to length to just fit up to the roof, and got a first lick of white paint. They’ll get a second coat and a wash or two in due course.

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That’s all for now folks…..

 

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