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Type7 - Robbe Rebuild.

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Type7 - Robbe Rebuild.

Postby subkraft » Sun Jan 26, 2014 7:07 pm

Hi y'all from Australia.....
I've been lurking and loitering on here for a while now, learned a lot, so maybe now time to post something.

Some years ago I did a Robbe U47, my first sub. Probably not the best choice, but, hey, had to have a U Boat. Replaced a lot of it, one of those beautiful etch brass decks, conning tower from Accurate Armour....a lot of resin to be ground out to make that work.

Then converted it use a Engel piston tank. As a working model it was never much good. It was a cut up of the Robbe wtc piston tank filled from the rear, so sub always went down stern first....overpressure, huge turning circle, not much space for adequate batteries, direct drive...many shortcomings.


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So, new project....Build a new wtc for it.

Through my work I use cad daily. This has extended to using a laser cutter to make parts. Signwriters often have them now to cut out acrylic lettering. Perfect.

I've built all the parts as 3d models and designed a new wtc to address the problems. The set of parts have been done and redone a few times to get the fit right. Now I have what looks pretty much like a final set:

Image

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For those familiar with the Robbe model....the bulkheads sit on a standard plastruct section which sits over the beads on the bottom of the tube. All these pieces are held apart on threaded rods.

Decided to post it as a build here....will keep me at it!

CNC, lasering is a fantastic process. I could never make it all by hand. Worst thing about it is the acrylic cement. Fumes awful....never thought I'd wind up making model parts dressed like the guy in Breaking Bad....
“The difference between genius and stupidity is that genius has its limits.” ~ Albert Einstein.
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Re: Type7 - Robbe Rebuild.

Postby Sub culture » Mon Jan 27, 2014 6:50 am

Looks very neat and tidy. I think the main issue with the Robbe was always the way the o-ring was compressed using the tray as a stressed element. This was okay as a dynamic diver, but once you introduce the internal pressure created by a retracting piston tank it puts a lot more strain on the mechanism, which to be fair to Robbe wasn't designed with that in mind.

So what ballast system will you be using this time?
'Why are you staring at an empty pond?'

Want to dive your boat in crystal clear water? Then you had better Dive-in- http://www.diveintomodelsubmarines.co.uk
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Re: Type7 - Robbe Rebuild.

Postby Ober Freak » Mon Jan 27, 2014 3:58 pm

Very nice one!

I also own a Robbe Type VII, it was the first sub of a friend of mine, we build it right oob, back in 2001.
After a while we replaced the forward battery with a soldered dive tank operated by a Bruggen hose pump system with the pump direct in front of the tank.
Dives really slow 90 sec or so, but was good enough for us school guys that days.
I got it when he moved away.

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Re: Type7 - Robbe Rebuild.

Postby subkraft » Mon Jan 27, 2014 9:09 pm

Thanks....

Aim of this is to get the piston tank working.

Stressing the equipment tray to get a seal on the endcap sufficient to resist the overpressure of the piston is the problem.
Its entirely dependent on the quality of the joint between the endcap and the tray.
My idea here is to make a better joint here...and to pull the end cap down all round equally.

Previously I used to close the piston, then bleed off the presure via bike valve on endcap.

Got a bit together...

Gearboxes from model aircraft, getting it to fit was a bit of a juggle....




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“The difference between genius and stupidity is that genius has its limits.” ~ Albert Einstein.
subkraft
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Re: Type7 - Robbe Rebuild.

Postby Ober Freak » Tue Jan 28, 2014 6:59 pm

Brüggen offers special bayonet lock rings for the robbe wtc http://www.modelluboot.de/Zubehoer/Bajonettver_e.html
may this is an attempt to solve the pressure problem due to the operating piston.
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Re: Type7 - Robbe Rebuild.

Postby subkraft » Tue Jan 28, 2014 9:48 pm

I did buy one of those intending to use it.....it's still in the spares drawer....

It would be an interesting job to retro fit it to the end of the main tube. You have to shorten it by 10, 15 mmm.
Easy enough to do before you put the hull together....but after the hull assembled? Probably have to make somesort of tool to do it from the
inside.

The actual o ring on the fitting seems very fine in section.....I did wonder if it would really do the job. Once done, there's no going back, lol.

Anybody done this successfully?
“The difference between genius and stupidity is that genius has its limits.” ~ Albert Einstein.
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Re: Type7 - Robbe Rebuild.

Postby Sub culture » Wed Jan 29, 2014 8:16 am

They work very well, seen a couple of them fitted, and of course the bayonets fitted onto Engel kits.

Very difficult to fit on a completed model though as you say.
'Why are you staring at an empty pond?'

Want to dive your boat in crystal clear water? Then you had better Dive-in- http://www.diveintomodelsubmarines.co.uk
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