Your welcome, simply pointing out there is an alternative starting point and seeking clarification on the fins. As this is a Mk III build do you know whether that engine type had 5 or 7 fins? Just wondering when the change occurred.

Never suggested that you can't build what you want Mike, we all build what we want to build, not sure how you got that idea.

Anyway have fun.

Al

This looks great. I finished one Mk. III while ago, it was russian lend lease vehicle. Got other uparmored and upgunned version of Mk. III in stash. I'll be following this as well

@ Jess: It's nice to see you checking in on this build. Hope you're finding your modeling muse these days with something good on your workbench. Safe travels and hope to see ya soon at some AMPS event in our region.

@ Darren: Glad to have you along, too. Hopefully you'll find some of the additions, tangents and segues to the Churchill portion of the project interesting.

@ Tomi: Sounds like you have some interesting Churchill projects of your own in the works. Maybe you'll see something here that will help you or give you some ideas.

@ Al: Sorry if I misunderstood the intent of your posts. You seemed to be implying that I was wasting my time by scratch-building the gearbox compartment rather than taking your route with the ITA set.

Also, I missed any question you intended to ask about the steering brake fins and took your comments to be technical criticisms of the accuracy of my work.

To answer your question:




The short answer is no, I don't know for certain which Churchill marks got which steering brake drum version or when. However, I do have some ideas on the matter.

The "long" answer requires total speculation on my part since none of the available references offer the technical details.

As total speculation, I would guess that the steering brake drum with the single, thick strengthening rim / cooling fin was the early (perhaps initial) design. After some operational use, I would imagine that experience indicated that the steering brakes were overheating (perhaps even leading to poor or failed steering), so the cooling fins were specified in a redesign of the component.

Now, as to the number of fins - I can imagine two possible scenarios.

One is that the numbers simply varied according to the subcontractor making the parts. That is, the redesign / new specification simply required cooling fins across the entire width of the brake drum without saying exactly how many. In this case, it could be possible that steering brake drums with 5 (4) or 7 (6) fins were used at the same time. This would not be out of character for the manufacturing situation existing at the time. As long as the part was made within the specified design requirements, minor variations allowing for each manufacturer's local processes seemed to be common and acceptable.

(Note 5-4 or 7-6 cooling fins is to recognize that what appears as the innermost "cooling fin" on those drums installed on the gearbox is really the circular mounting on the end of the gearbox and is not actually a fin on the drum itself.)

The other possibility is that the smaller number of fins (5-4) was an intermediate design and the larger number of fins (7-6) was the later and final design. This assumes that the larger number aided in additional cooling over the smaller number. Also, the photo evidence from restored Churchills all seem to show only the 7 (6) finned brake drums which suggests that these were the final part design (being the most likely to survive as available spares or the final replacement parts installed).

So - again, pure speculation on my part - I would submit in the absence of evidence to the contrary, the single-fin brake drum is the initial design, the 5 (4) finned drums are the intermediate design, and the 7 (6) finned drums are the final design. Each representing an improvement in the capacity of the brake drums to cool off in use.

As to when each steering brake drum variant was introduced into production, and continuing my speculation, I would guess the initial design was used on the Churchill Mk. I and II and possibly the early III before the major re-build program was started. After the major rebuild program started, I would guess that all Churchills received the 5 (4) finned drums, and then beginning not later than the Mk. VII (because of its increased armor and other major revised components) the 7 (6) finned drums were introduced.

Furthermore, I imagine that all of these steering brake drum designs were interchangeable, that is, a "later" drum could be installed on a tank as a replacement for an earlier drum.

This would probably have been a quite common maintenance operation - renewing the steering and main brakes, and once the old brake drums were too worn to be turned, I'd guess that their replacement was fairly common. In fact, the quick-fix in the field would probably have been to replace the brake components with new or renewed parts to the get the tank back to the user ASAP, and then take the removed brake drums, machine them back to a serviceable state, and put them back into unit part stores for the next tank.

Churchills seemed to have had very "robust" service lives and brake maintenance would probably have been fairly routine.

However, until someone publishes an in-depth reference on the Churchill, one that actually provides these kinds of details, all that can be said with certainty is that the steering brake drums had several design variations in regards to the presence and numbers of cooling fins.

What Churchill fans really need is a new, comprehensive reference work along the lines of Dick Taylor's "Into the Vally." There are a lot of unanswered questions about the rework program, such as when the various rework features were introduced into the rework program and on the primary production lines, and what are the detailed meanings of the various reworked serial number suffixes, etc?

It seems clear that the rework program tanks did not all receive all of the same modifications when they went through rework at different times. Modifications were introduced incrementally into both the rework program and regular production. However, what all of these modifications were and the sequence and timing of the introduction of them remains unclear.

Because tank serial numbers cannot be used to sequence a tank in the rework program, it's very difficult to sort through photos of different reworked tanks to try to determine when visible rework / production modifications were introduced. You can't simply take a picture of two reworked tanks and say, "This tank with the lower serial number was reworked first therefore the reworked features on it came before the features on the other tank."

Surely, someone was keeping track of these modifications during the war, and the various serial number rework suffixes suggests that there were some standards applied to identifying certain "blocks" of tanks that had undergone rework (perhaps multiple times). Sadly, though, no one has published a reference to give us these details.

Another example of the lack of detailed references would be Shillito's work in identifying the detailed differences between Churchill turrets even within the same marks. Shillito has done excellent work in this area, but thus far, no one has taken up on that work and put it into a really good, printed Churchill reference.

With the Churchill, sadly, the answers don't seem to come easy.

Some progress on the gearbox today.

I finished shaping the main body part of the gear box, and then added the fins or ribs.

If the basic gearbox shape was a regular square or rectangle or if it otherwise had flat sides, adding these ribs would have been a straight forward task of applying strip stock along the sides.

However, the Churchill gearbox is really oval-shaped when looked at it from the end elevations. What's more, while the back edge is a regular semi-cylinder, the front edge is not only rounded, but its corners are tapered. This means that the ribs are irregular crescents.

Cutting these out individually and then fitting them neatly to these curved shapes on the gearbox would be a very hard job. There is an easier way, though.

What I did was to mark out the locations for the ribs along the front and back edges of the gearbox. I then made a quick jig to hold the gearbox plumb and horizontal in my miter box.

Because the box is small and there's little room to get a good grip to hold it steady, I clamped it in this alignment jig and in the miter box. I then used my saw to cut slots into the basic gearbox. These slots will accept pieces of either .010 or .015 thick styrene sheet that will be formed into the curved ribs.

Here's a picture of my gearbox in the jig clamped into my miter box.



The metal ruler is used to give me a flat surface inside the bottom of the miter box which helped to get everything level and plumb for the saw cuts.

Here's a shot of the saw in action.



At the same time that I marked out the locations left to right for the ribs, I also marked out how deep to make the saw cuts.

Once the saw cuts were made, I added pieces of styrene into the slots. These don't need to be neat, they do, however, have to be large enough to make the ribs.

These are the rib "blanks" glued into their slots.



I allowed the glue to set for a bit, and then trimmed up most of the excess so that I could test fit the top and bottom halves of my gearbox.







Up to this point, I've kept the top and bottom halves of the gearbox separate just because I found it easier to handle them and compare their shapes to pictures of the prototypes.

Once I get the ribs shaped, I will glue these together and then start work on some of the other cast-in details, such as tubes that accept bolts and the gearbox lifting rings. After all of the cast details have been added, I will coat the gearbox with thinned putty or Mr. Surfacer to replicated the cast texture and blend all the various parts together.

So, that's all for today.

Happy modeling!

I don't know where you manage to find all the time needed to review the vast ammount of reference material and then add the construction time. Every time I talk to you on the phone, your in the outback trimming trees, bushes and ground cover or as you call it, 'clearing the arcs of fire'...

But anyway I love this work and no doubt it is going to be a stunning piece of work.

Your typical methodical approach gives me the boost I need to finish one (any) of the many projects sitting around my work bench Mike.

Keep up the good work and I will see you Wednesday.

Keith.

@ Keith: I don't know, my friend, I think research is an on-going, constant endeavor. I've been doing research on this build (or up-coming parts of it) for a couple of years.

And right now, as I build this beastie, I'm doing research on some other potential future projects. Guess it never stops...

(Kind of like the encroaching forest around the ol' hacienda - chopping back those fields of fire and keeping the perimeter clear never stops around here either!)

Anyways, some more incremental progress on the Churchill gearbox.

I've shaped the ribs mostly by trimming with a pair of finger nail clippers and sanding. I've also added the bosses for the various through bolts and the lifting eyes. I've added the fitting on the right hand bottom side, too. Not sure what this is, but it appears to be a small circular sump or perhaps an oil filter unit. It seems to line up with one of the round access plates on the hull bottom, so I suppose it's a routine serviceable component.

The bolt and lifting eye bosses are made from round styrene rod inserted into holes drilled into the basic gear box after the ribs were shaped. These were allowed to dry overnight and then cut and sanded to their final lengths. The round fixture on the bottom was a section of styrene tube also inserted into a hole drilled into the gearbox and trimmed to length after the glue dried.

I've given the basic gearbox a coat of Mr. Surfacer 1200 to fill small imperfections and blend all of these parts into what will hopefully appear (under paint) as a unified cast metal structure. I'll clean this up after the Mr. Surfacer dries hard and touch up any remaining small pin holes and other imperfections (like the seams around the rear mounting "ears" where I've added extra material).

But, this pretty much wraps up the basic gearbox shape. From here, it's a matter of added the details to it. These details are mostly bolts, the air compressor, and the shifter linkages and shifter mechanism covers.

In this direction, I've begun the glue-up for the air compressor that sits on the top left side of the gearbox. The Churchill used pneumatic actuated main and steering brakes as well as a pneumatic clutch actuator. This air compressor supplied the required compressed air.

The compressor has small cooling fins on the pump part of the assembly, and these will be made from one of the pieces in the photo. It's simply strips of .005 plastic, 1 and 1.5 mm wide glued together using the same scratch-building approach as the steering brakes to get the finned-look.

The other part is the "tombstone" body of the compressor and the cylinder that connects it to the actual air pump. These parts will need to dry overnight before I can do some more shaping of them.









The gearbox is a very complex shape, but hopefully this brief description will give you some ideas about how even complicated components can be broken down into manageable steps. These techniques are all just "old school" modeling and well within the capabilities of most modelers.

Happy modeling!

Last few build session have concentrated on the air compressor that sits atop the gearbox.

I'm almost done with this detail. Just a couple more bolts to add and a wee bit more clean-up. Here are a few happy snaps:









And to give you an idea of the size of the part in scale:



The entire compressor is about 8.9 mm long.

Happy modeling!

So amazing, Mike!

I think, with the exception of Steven Davie's Tiger I, this is the most thorough build I've seen yet.

Really looking forward to watching this one.

@ Christopher: Thanks for the props! It's been a fun project so far, and I'm learning new stuff about the Churchill everyday.

I just figured out the devices and details for the speedometer, which might not seem very interesting to some others, but it will add more details into the gearbox compartment.

Curiosity and info about one thing often leads to understanding another, and so on... I enjoy the research and challenge of figuring out how these things worked and then how to model them. Like I said, a fun project.

Anyways, glad you're finding the build worth checking into. I hope it continues to hold your interest.

Happy modeling!

So, progress over the last few build sessions has mostly been about geometry and the general layout of the gearbox compartment space.

An interesting feature of the Churchill (at least I found it so) is that the engine and driveline do not sit level in the tank. Here's a description of this from the operator's manual (see Montgomery's "Churchill Project" website):

"Viewed in side elevation, the crankshaft and transmission centerline is arranged at an angle of 3[degrees] 56[minutes] to the horizontal, the slope being downwards to the front of the engine."

This accounts for the angles that can be seen on the rear bulkhead between the engine and the gearbox compartment. This wall (which creates an "air dam" to ensure proper flow of the cooling air) is angled or sloped with its top forward of its bottom. Along its sides are narrow, vertical triangles.

Here's what the operator's manual says about this wall:

"The rear bulkhead carries a cowling for the cooling fan, and this cowling is made in halves to permit assembly."

In order to replicate these features on my build, I rounded the drivetrain slope to an even 4 degrees and used that angle to rebuild the bulkhead in my model's hull.

Here are a couple of pictures of the rebuilt wall:





There are still many details to add to the visible side of this wall, but this is its basic shape and location (dry fir for now to allow the gearbox to be installed and removed).

After some drafting to figure out where the downward sloping input shaft and clutch will be located on the bulkhead, I added short input and output shafts onto the gearbox.

These shafts will fit into holes on the main brake drums and the bulkhead. This will allow me to suspend the gearbox in alignment with these components and measure to build its mounts (two in the rear and one under the collar around the input shaft). It might seem backward to connect (dry fit) the gearbox to the brakes and bulkhead and then make its mounts, but using this sequence, I will get the mounts to fit the gearbox's required location. If I had had a set of scaled drawings of these components, then these parts could have been made according to the plans with the parts fitting as designed. This is the kind of construction sequencing that's necessary when working from photos and allowing for the kit's design features (wall thicknesses, etc).

After I added the front input shaft, I started on the collar that connects to the front of the gearbox. This collar will have a "saddle" around it that holds the clutch actuator and that sits on the front gearbox mounting point.



I also started work on the face of the clutch that can been seen inside of the fan. I still have to add six radial levers and some bolt details, but this picture will give you an idea of where the build is going in this location.



Throughout all of this, I've been going back and forth dry fitting various parts and making adjustments on their fit.

These pics show the angled bulkhead and gearbox fitted. You can get some ideas about how this angled wall and the triangular facets on either side change the look inside the compartment. This is also how I will position the gearbox in order to measure and build its mounts.



This side view shows to good effect the downward slope of the drivetrain.





Also, now that I have these fundamental elements positioned, I can work on some of the other details which have to be fitted into the space.

Happy modeling!

Love it Mike, can't wait to see this in person next Wednesday.

Keith.

Nice work with the white plastic. You have also displayed some interesting techniques. I like the embedding of the cooling fins into the gear box body for ease of assembly.

I need to sign you up for a scratchbuilding seminar for next year. Keep of the posting and the work. my only wish is to be able to see it without the coat of paint and weathering but I don't see myself in South Carolina any time soon...

JC

EXCELLENT work, Mike!

Your scratch-building skills are wonderful, and you're approach to making parts from plain plastic seem oh so simple.

I look forward to seeing this at our club meeting Wednesday evening.

@Keith: As always, I appreciate you checking in and your comments. I'm looking forward to the meeting and seeing how you're coming along with your snowy Scorpion.

@John: Thanks for the props, too. I don't always find the easiest way to do these things, and sometimes there just is no easy way.

In regards to adding the ribs the way I did, I couldn't figure out any other way to add them that wasn't insanely time consuming or that could have gotten close and neat fitting between the ribs and the body of the gearbox. In this case, I think the easiest way also produced the best results.




LOL! You must be getting desperate! If you're serious, though, let me know off-line, and I'll see what I can do.

@ Jeff: You snuck a comment in on me as I was adding this post... you crafty devil, you...

Hey, you're no slouch yourself when it comes to this stuff. I'm still waiting for you to post up some of your Japanese APC work. You've got some pretty impressive scratch-building there, yourself!

Looking forward to seeing you Wednesday. Thanks for checking in.

So, on to the Churchill...

Since the last up-date, I've built the rear gearbox mounts. These are pretty straight forward work. The design is a basic inverted, right-angle "L" with mounting pads on either end and a gusset inside the angle.

With the gearbox dry fitted in the compartment (see the last post), I measured up the distance from the rear hull wall to the gearbox mounting pads and the distance from the pads straight down to the bottom of the compartment. After checking through my stock of styrene strips, I selected .015 x .060 styrene strip as a fairly good "proportional" match for the stock used to make the prototype mounts.

(That is, the styrene strip looked about the same size as the stock on the prototype when I held the strip in the model and compared that to photos of the real thing.)

This first photo shows the basic mount shapes glued up. Note that the bottom pad is at 60 degrees to the vertical leg because the bottom of the mounts attach to the angled lower hull and not the horizontal compartment floor.

You can see how I used two drawing squares to line up the parts as the glue was setting.



Inside of each mount is gusset. In this photo you can see how I started to layout the stock for this. The sides of the gusset are the same length as the inside of the top leg of the mount. So, easy-peasy... A square cut diagonally into two parts will make two identical gussets.

To layout the square, I used a metal straight edge and held one edge of the sheet styrene tight against it. I was then able to use the metal straight edge as a guide to hold my squares, well..., square.

Four right angles later, and you could say I was all "squared away"





The square was cut out and then divided on a diagonal for the two matching gussets.



These were glued into the basic mount shapes and the mounts were set aside overnight to dry.

This is an important point - With scratch built parts that are aggregations of many small styrene bits, building in stages and allowing the glue-ups to dry completely allows for neat and clean final shaping. A degree of patience is required for this.

These gearbox mounts will be sanded flat on their sides to square up each side. I will then sand small radiuses on the corners of the mounting pads and very slightly relieve the edges. Finally, I will sand the attachment surfaces of the mounting pads square and flat for a good fit in the model. All of this final shaping and finishing requires that the mounts be hard dry so that they can withstand the handling and the glue joints will sand cleanly.



Once the glue was dry, the mounts could be sanded into their final shapes with the joints between the parts cleaned up and the rough edges smoothed out.

I then installed them into the tank using the gearbox as the alignment "template." That is, the mounts were installed to match the gearbox and not the other way round.

While waiting on the mounts to dry, I commenced work on the what is probably one of the most complicated details - the notorious "Sirocco" cooling fan.

The cooling fan in the Churchill is basically two truncated cones, one inside the other, with the fan blades between them and holding the cones together. It took me quite a while to work out the geometry and dimensions. A lack of good photos, that is, photos taken directly from the sides or top and from the front and rear made the job of figuring the features fairly difficult. Each of the two cones is different in overall diameter as well as depth.

Eventually, I went to the cutaway maintenance drawings in Montgomery's book, scaled them using measurements from the kit, converted to prototype dimensions which were then divided by the same measurements taken from the book drawings.

(BTW: The upper drawing scaled out to 1/49 and the lower to 1/46.)

I won't list all the dimensions here except to say that I did use 60 degrees as the angular measurement for the cone shapes. Anyone specifically interested in the math may feel free to PM me or post up questions in this build blog. No secrets, just that the results are even more long-winded than my usual!

With some sketches and dimensions, I was ready to form the main fan parts. In order to make these cone shapes, I decided to vacuum form them. This is a good technique for complex shapes, but it does require a lot of work.

I had to make two forms since each cone, the inner and outer, was different. I turned these forms from brass stock and the form with the deep shoulder and deeper cone required some air holes drilled radially so that the vacuum could suck the sheet into the angle.

Here's a picture of the two forms removed from the vacuum formed sheet. The deeper, inner cone has been cut out of its form and the shallow, outer cone is still wrapped around its form. On the deeper form, you can see the radial air holes where the shoulder and angle meet. These holes go to a larger, center hole.



Here the inner cone has been cleaned up and test fitted around the clutch.



And a close up of the inner fan cone and clutch. You can see that I've added some details to the clutch since the earlier post. The clutch and the shoulder portion of this cone will actually fit through the bulkhead between the gearbox and engine compartments.



Here the second, outer, but shallower cone has been cleaned up and removed from its form, which is now clearly visible. Because this form was so shallow, it did not require the air vacuum holes needed for the deeper form.



Finally, here's a test fit shot of the fan cones. Also visible are the two rear gearbox mounts. The critical check here was to ensure that the larger diameter, outer fan cone did not touch the floor of the gearbox compartment.



When completed, the fan will not protrude so far rearward into the compartment. The cylindrical portion of the inner cone and the clutch will be positioned through the bulkhead and the outer fan cone will touch the wall.

(In reality, the actual outer part of the fan also goes through the wall, but since I'm only showing the gearbox compartment up to the bulkhead, I don't need to actually put the outer part of the fan through the wall.)

The next couple of build sessions will concentrate on assembling the fan with its blades holding the two cones together.

Happy modeling!

This is really impressive Mike. Great job.

@ Jesse: Thanks, buddy, I appreciate the kind words.

So, first up today is a new reference book:

Vauxhall Motors. "Driver's Handbook for the Churchill Infantry Tank." Reprint of June, 1943 edition. Periscope Film, LLC. No publisher's origin. 2012. ISBN: 978-1-937684-73-0

My copy from Amazon.UK came today. It covers the MK.I-IV and includes numerous sketches and diagrams, most of which have been published in other sources. In particular, Montgomery's Hayne's title contains most of these drawings. However, I've already found a lot of small details that I've not seen before, so to me worth the US$21 (including shipping from the UK to the US).

On to the build...

Today was cooling fan fan-blade day. The first order of business was to layout the fan blade locations. The prototype fan has 16 blades. This works out to a 22-1/2 degree spacing between blades. Well, my dividing attachment won't do 1/2 degree increments, so I was left with either 18 blades (at 20 degrees each) or 15 blades (at 24 degrees each). Fifteen being closer than 18 to 16, I went with 15 blades as the lessor of two evils for my fan.

I also had to estimate the angle that the blades are installed between the inner and outer fan "cones." This is another compound angle that's impossible to calculate without at least a couple of known references. In the end, I just swagged it, going with an angle that "looked" right when compared to the few available photos.

Here's my inner fan cone placed on its form with the fan blade locations laid out. The pencil lines roughly connect inner and outer prick marks that are made 24 degrees apart, and it's these prick marks that were actually used to line up the fan blades. The pencil marks are mostly a visual cue so I don't screw up.



Along each blade's location, I added strips of .005 styrene to replicate the flanges on the blades that are riveted to the fan body.



While the glue was setting some on these flanges, I cut out the fan blades. I started with measurements taken from my working drawings, but because of the compound angles (the angles of the cones, the four different diameters, and the tangential lines across these cones that the blades are installed along), trying to calculate the precise final shapes would have been too time-consuming...

("Damn it, Jim! I'm a model maker, not an engineer!")

So, armed with the known length (the same measurement as the flanges) and width between the cones (off my drawings), I commenced to trial fit three blades.



I installed three by "tack" gluing at 120 degree intervals (i.e. 5 fan blades apart) and then test fitting the outer fan cone. I trimmed these three blades until I had a fairly close fit. I then transferred these new measurements to the remainder of the fan blades and installed them.



I allowed the glue on these to set up a while and then I test fitted the outer fan cone.





I will have some final sanding to do to get a tight and neat fit, but these last two photos will give you some idea of how the fan will finally look.

So, until next time...

Happy Modeling!

So, how soon till engine testing starts? What's it gonna run on, gas, diesel, multi-fuel?

You might want to check out The Churchill Project on Facebook. They're doing a private restoration of a Mk. V I believe, and they've been adding photos as they go. Even if you aren't a Facebook user you can still access the page.

@ Christopher: Well, according to the Driver's Handbook, we'll need 182-1/2 gallons of at least 75 octane petrol. Let's see, in 1/35th scale, that'd be...

Thanks for checking in!

A bit more work on the fan:

After some additional work on the outer fan half, I made a simple glue-up fixture. This was really not much more than a piece of thick styrene with a hole in it, the diameter of which was between the max and min diameters of the outer fan half. This fixture hold the fan evenly around its circumference. It also makes a nice reference table to adjust the fan parts so that they are evenly spaced from each other around their edges.

I left the inner fan half with the blades on its brass form, suspended the outer fan half inside the hole of the gluing fixture, placed the inner part on top, and allowed the brass former to weight the assembly. I inspected the fit of the fan blades and made some adjustments by sanding some of them until I got an acceptably good fit. (The pencil marks on the gluing fixture were made to help me keep track of which fan blades need adjusting.)

Once I had a good fit, I used a couple of small rubber bands to hold the two parts together while I applied the glue. I left the fan with the rubber bands around it in the fixture to dry.



The fixture held the parts in alignment well enough that I could go around and add the fan blade flanges to the inner fan half.

After this glue-up dried over night, I laid out the lines of rivets that hold the fan blades in place. The first step in this was to mark the locations of the outermost and most inner rivets on one blade.

Once I had these two marks, I held the fan steady and used a compass to mark to concentric lines across these two points. I then connected the two points with a line and measured it. I divided this length into the segments that the rivets will be spaced at (5 rivets about 1.15 mm apart). I marked these locations along the line.

I then set my compass to mark three more concentric lines across these inner rivet locations.

Next, I used my dividers set at the distance between the outer and inner ends of the fan blades and "walked" the dividers around the inner and outer circles to mark out the locations of the ends of the fan blades. These points were then connected by lines.

The locations where these lines cross the five concentric circles are the points where the five rivets for each fan blade will go.



The rivets were punched from .005 sheet styrene using a .018" punch and die (Waldron Sub-Miniature Punch and Die Set). These were glued on and the clutch was finally added to create a single clutch-fan assembly.





My intention is to make a single sub-assembly consisting of the gearbox, the muff couplers between the brakes, the clutch and actuator and fan. This assembly can be finished outside of the model, and then installed into the finished compartment. This will sit on the rear gearbox mounts with the front end (fan and clutch) resting in a hole in the bulkhead wall.

Here's a test fit of this assembly at this point.



And the same assembly test fitted into the compartment.





Happy modeling!

Mike,
When are those very nicely constructed parts going to be sent to the caster's for duplication??

Seriously, nice work. I was just commenting to Chuck A about your lathe/mill, that was present in your workshop pics on the AMPS forum. Good to see that you can and did put it to use.

John

I really enjoyed giving your model a close 'once over' while you were loading up your truck after the AMPS meeting and I can honestly say it is amazing and the end product worthy of your masterful skills and dedication.

So your NOT going to get it finished this weekend then?

I hope the NEW mitre box, saw and metal angles that you purchased from me helps with future items that require precision cuts.. The fan looks great.

I love the old Churchill tank and this one is going to be amazing.

Keep up the good work and keep the updates coming.

My Scorpion is limping along (slow progress, but hey, the weekend starts today for me).

Keith.

Mike, Now I know your showing off! LOL.

Very impressive work!!! I'm really hooked into this build

@ John C: I've had my lathe and milling machine for over 25 years. It's been good kit, and I've used the heck out of it over the years. I think that some of my machining operations would make a real machinist cringe, though!




LOL! I guess that mostly depends on some resin caster willing to "do a deal-deal"...

@ Keith: I appreciate your comments, my friend. I'm developing a fondness for the ol' Churchill, myself.

@ Big John: It's good to have you aboard and along for the ride!

Before getting to the build stuff, I've added yet another reference for the build. I found out that the Tank Museum published a Churchill companion volume to their Cromwell book. It's long been out of print, but once I knew to look, tracking down a copy wasn't too hard.

The Tank Museum. "Churchill Tank: Vehicle History and Specification." Her Majesty's Stationary Office, London, 1983. ISBN: 0-11-290404-1.

The contents are mostly an abbreviated reprint of the "Service Instruction Book: Churchill VII & VIII." However, the reprinted parts include large amounts of information on the components common to all marks. If you're interested in the details, this would be worth your time and effort to find. (The Cromwell book is pretty good, too.)

So, on the build...

I've spent the last few workbench sessions on the collar and saddle for the gearbox input shaft. The saddle portion of this component serves the duel functions of supporting the front of the gearbox on its front floor mount and carrying the clutch actuator and the mechanism that operates the clutch release bearing assembly.

To make the input shaft collar, I glued up a styrene mounting plate with a tube and sections of sheet that will be formed into the flanges that radiate from the collar.



This assembly was given a coat of Mr. Surfacer 1200 and allowed to dry overnight.

At the same time, I made a rough glue up for the saddle that sits under and around the right / starboard side of the collar.



This was also set aside to dry overnight along with the front flange and the pulley for the belt that operates the turret traverse motor generator (mounted on the floor of the gearbox compartment). This last part was simply made of a stack of styrene disks of various diameters. It was necessary to allow this to dry hard so that I could drill a hole through it later.

After drying, these three basic glued up sub-assemblies were shaped by sanding, filing, carving, and drilling into their final forms. They were then glued together and detailed with some bolts punched from sheet styrene.



This collar and saddle assembly slips over the input shaft on the front of the gearbox.

There is a short visible portion of the shaft between the gearbox and the clutch release bearing which is splined and surrounded by a coil spring. I made the splines on the styrene tube shaft already installed on my gearbox by using a razor saw like a small broach and simply cutting the grooves and leaving the splines.

While waiting for some of these glued up parts to dry, I added a light cast texture to the gearbox body using Squadron Green Stuff polyester putty thinned with lacquer thinner. This has a "grainer" texture than the Mr. Surfacer and makes for a nicer cast look.

I also added the numerous bolts and plugs on the gearbox.

All of this was test fitted in order to gage the space between the rear face of the clutch (inside the fan) and the front of the input shaft collar saddle. The clutch release bearing assembly and its operating levers must be fit into the available space, and that's the next job...





(Sharp eyed viewers might notice that I've also added the fan blade rivets to the outer fan cone. I noticed that this will be visible once the build is completed, and I laid out and added these rivets exactly the same as the ones on the inner fan half.)

Happy modeling!

This is so good it makes me feel like it might start up any moment.

Great work Sir.

Keith.

amazing build so far, I love all of the details added to it. Also how did you make the compressor at such a small scale ?

@ Keith: Always appreciate your comments and encouragement!

@ Tommy Thanks for the props!




This is kind of a tough question to give a simple answer to...

Speaking for myself, I think one of the keys to fabricating styrene components is always trying to work with the largest pieces possible. This means not cutting pieces to their final sizes until you really have to.

If you need a very small piece of styrene strip that has a hole or some other shaping along its edges or end, the easiest approach is to shape the piece while it's still part of the long strip. This way you can hold it firmly while drilling, sanding or filing.

Other times, it's easier to glue the styrene shapes together only worrying about getting the joints and seams cleanly fitted. Once this conglomeration has dried hard, the styrene bits can be shaped while you have a larger component to handle and hold.

Often times, I'll do several of these "glue-ups," and once each has been finished, I'll bring them together to make the final component.

(This was also the approach used with the gearbox input shaft collar and saddle, above.)

So, here's an annotated photo of the glue-ups I started with in making the compressor. The numbers are the sequence that I performed the steps in.



These look quite rough at this stage, but once they were dry, I had parts that I could work on that were large enough to handle.

Note that the "tombstone" shaped part was curved while still part of the strip and was cut to size after the curved top was done.

The tube and flanges were shaped to their final length after they had dried on the glue-up. So, rather than trying to cut a piece of tube about 3 mm long with perfectly square ends to a precise length, I concentrated on getting one end square and cut the final length later. That way I could also use the "tombstone" and base plate as guides to get the second end of the tube square.

The approach to the finned compressor head was similar.

I glued up stock to make the finned parts and allowed these to dry. All that was important was to get the alternating strips glued to each other cleanly. Length and thickness were not critical at this time.

(The piece in the photo is just one of these that I glued up. The main part I used was 5-6 times longer to make it easier to handle.)

Once these finned strips had dried, I sanded them down on the backside until they were only about .75 mm thick. This made finned strip stock that I could use as a "textured" appliqué to the basic compressor head glue-up rather then try to cut dozens of little fins to precise sizes.

So the compressor head is really two pieces of rectangular stock, a larger one that connects to the tube on the earlier glue-up, and a smaller one, .75 mm smaller in length, width, and thickness than the final finned part.

These two rectangular pieces were glued together and the thinned down finned stock was cut into pieces and applied around the smaller rectangle. Once this had dried overnight, I used a fine saw blade made from a modified X-Acto #11 blade to clean up the corner fins.

Here's a diagram of this modified #11 blade-saw.



It's made by putting the blade in its handle and then using the metal cut-off wheel on a Dremel rotary tool to lightly cut the notches leaving the teeth. This blade will make a very fine notch, the width is controlled by the depth of the cut.

Here's a diagram showing how this blade can be used to notch styrene rod to make flush screw heads.



(An article with a complete description of the technique for making slotted screw heads can be found here:

AMPS Central SC::Wildcat Newsletter::V1-N1

Scroll down to page 10 for the article.)

Once the compressor head was finished, it was glued to the "tombstone" part for the completed component.

Anyways, I hope this helps to answer some of your question.

Happy modeling!