A Folding Funny .... * * * Finished * * *

[Ian]

That is amazing work, John. Simply amazing!

[JohnRatzenberger]

Started by rigging the winch rope. I mounted the rear part of the bridge to the AVRE, lowered it past vertical, then ran my ropes -- this to get all the cables neat and to figure where to tie it off to the platform.



I had plenty of opportunity to play wind the winch and seeing how things went ….



Not bad, but as I feared the friction between the string/cable and the blocks, combined with the lack of scale weight on the bridge (despite the clamp hanging off it) meant that the cable always needed a bit of chiding to run neatly. I had thought about some sewing machine oil to see if that would help, but didn't try yet not wanting oil on an unfinished model.

Nonetheless, here we are with the bridge in its most raised position. It isn't as far up as it should go -- part of it is the kit pieces aren't sufficiently big to give more clearance between the bridge and the tracks. The other part is me - I used the kit instructions for cable length and I really should have made the primary and the single-block cables about 5-6mm each shorter to give me more room to wind the bridge upright.



OK, with the winch cable on, the rear section mounted, and everything working as best as can, it was time to mount the fore section and work with it to see if the cables would indeed pull the bridge open. Now up until now, I had been testing the "hinge" using a single brass rod through the hinges on both hornbeams and the motion had been pretty good. I even ran a drill through again to be sure the holes were clean.

I mounted the fore section using the two hinges, the fit wasn't as easy with the SBG mounted onto the AVRE. I put no glue near anything. Happy that it was together, I tried to move the fore section to see how easily it swung ….

AND TWO HINGES BROKE on one side and one cracked on the other ….



And that is fatal to a working model, there is no repair.

What went wrong ? Well, obviously I should have tried brass hinges. I knew the plastic was dicey but I had taken great care with the design and to not "injure" those hinges in any way. I suspect as long as I was using the single long brass rod, the inherent weakness was distributed along all four equally and a degree of rigidity between each pair of hormbeams and the two platforms established. Once I went to two hinges, I lost that and it failed.

So, I lined the platforms up as best I could and dumped some CA in at the hinges. When it's dry tomorrow and I get over the urge to bin the whole thing, I'll finish it up as a non-working, not particularly scale representation.


Naughty words.

[Ian]

The naughty words do not surprise me, John. That is a real pity because the work you have put into this build is exemplary!

[lancfan]

Rotten luck John, even as a static it will look great- maybe you will have a go at another bridge later?

David.

[JamesPerrin]

A real shame John, but I think you've proved in theory that it can be all made to work. Even as a static model it will look splendid.

[ntrocket88]

Well at least we got to see the superb work you did to make it all work, however briefly! While it is very frustrating for you to come so close, you have still produced a fantastic model and finished it beautifully.

[Dirkpitt289]

Amazing work, John. Simply amazing.

[SJPONeill]

The development of this model has been inspiring, John and more so considering the itty bitty fiddly widdly scale that you have done all this work in - in its current position it would form the basis for a diorama that shows off the mechanics of the bridge mechanism, with a couple of figures using much the same language you did when the hinges went - I'm sure that such or similar would have happened in real life...

Great job on this...what this forum is all about, pushing the boundaries of modelling

[philp]

Should have done the fascine.

Nah, just kidding. This was a fantastic build and lots of great modeling information.
Even the bridge breaking is a learning experience so get a non working finish and build the next one.

[JohnRatzenberger]

Thanks, guys ...

I'm really bummed, it would have been OK to break if it had just worked once or twice so I had the opportunity to study how the secondary cable worked and get a couple pix. I suspect it would not have done well given the friction problems I mentioned already, the fact that string will stretch under load, and that I just didn't have the real world weight to help things along.

Oh, well, I'll finish up next day or so ....

[JohnRatzenberger]

With the gracious extension to our GB by lancfan, I am proceeding, albeit with a later start than normal today as I read my papers, drank my coffee, and thought about rigging the secondary cables.

My thought, before yesterday was that if I really wanted it to "work", at some point I would have to simulate the blowplates on the primary and secondary to allow the bridge to drop the last bit, but of course, I'm not into 76-scale explosive charges so something else was needed.

I thought about making the rear sling from real wire, with a couple hooks to engage the secondary cables and at the right moment I could just slip the hooks and down it would come.

And that's the way I went with this, although working is not longer a goal. I started by running the bridge up about as high as it would go, but leaving some slack. Then I made a rear sling out of wire fishing leader bending it so it fit into the channel under the rear deck and neatly over the tubes designed to keep it off the hull. With that done, I ran the two secondary cables back, evened them up and chose a common place to form a loop in each.

Then, working one side, I put tension on the secondary cable causing the bridge to rise just a bit, measured where the loop met the rear cable and formed a small hook in the rear cable.



With one side rigged, I did the same on the other side, being careful to keep the cables taut. I did discover I made the loops a tad small and that it is hard slipping cut wires into string holes.



With both sides done, I could fiddle with the winch, taking that slack out of that cable ….



It's sitting now. I have put Future for the decals, painted white along the rails as many SBG were - note it is a sloppy job intentionally but I do have some touch-up to do. And I need to trim one side of the rear sling a bit, probably put a dab of CA to permanently join the cable/sling, and I need to fabricate some dummy blowplates. It's getting there, but I probably ought to hold off much CA'ing until I finish the decals under the front and rear hull.

[JohnRatzenberger]

Almost there. The decals are on, but I'm not happy. Despite a coat of Future they appear to be silvering and despite Micro-Sol/Set some of them do not appear to be laying down well, particularly the name & serial along the sides.

BTW, the markings are right from the kit, but are "bogus" because AFAIK the folding SBG only was tested, not deployed, and if it was deployed I have no idea of the unit or markings …





I am going to fight with the decals a bit more today, then probably lay down a DullCote and let it sit overnight -- the decals will be right or wrong and I'll relook in the morning.

The only thing I need to do, and that has to wait until the decal/dullcote issue is settled is rig the blowplates and I already have the parts cut for that.

So final is tomorrow, unless I get really lucky today ….

[philp]

I like it John.

[JohnRatzenberger]

3 coats of Micro-Sol/Set and 3 coats of Dullcote and still the turret markings were silvered. So I resorted to some semi-dry brushing and buried that under another DullCote and it's OK.



I rigged blast plates but I really didn't plan the connection of the rear sling to the secondary cables as the blast plates ought to be part of that. Nor do I like the wire I used, it isn't flexible enough.



But it's there, and here we have it ….



I undertook this project for an ulterior motive. I have a 1/35 AFV Club Churchill, a Resicast SBG, and some more aftermarket -- this little kit is/was the experiment to see what I needed to do to convert all that to a folding SBG.



The lessons learned here will hopefully keep me from a similar debacle with a lot bigger and more expensive model. Because I intend to build the 35-scale one for an AMPS contest (although not the one I planned on, ran out of time on that), it'll definitely not be a working model. The research I did for this one will make my life easier and has pointed me toward a few more items I need to look up. I do wish I could find some photos of a real folding SBG.

Enjoyed the GB - thanks David for leading it and thanks everyone for some really nifty builds, tips, and of course for your cheerleading ….

[lancfan]

Terrific build john, I know what you mean by wishing for a picture of the full-size machine- When I built my Churchil models I couldn't find any images of the real folding or towed SBG types either.

David.