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Author Topic: HMS Brocklesby semi scratch build  (Read 163282 times)

radiojoe

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Re: HMS Brocklesby semi scratch build
« Reply #150 on: December 13, 2015, 03:44:39 PM »

In between casting the fittings I've made so far, I've been looking at the next moulding project the four hydraulic derek bases, the dereks are about the only items not shown as a separate drawing, so after studying them at length I've come up with what I think they look like, the two forward dereks and the port aft one are the same size bases, the strd aft one is bigger, the forward two are made up of three layers and the aft two have the lower layer omitted, the photos show the forward two, and the port aft will not have the lower webbed plinth.
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ballastanksian

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Re: HMS Brocklesby semi scratch build
« Reply #151 on: December 13, 2015, 07:14:06 PM »

Brilliant work Joe. I think you have another potential product under development!
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Starspider

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Re: HMS Brocklesby semi scratch build
« Reply #152 on: December 13, 2015, 08:39:30 PM »

Got to go with ballastanksian comment impressive work.
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radiojoe

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Re: HMS Brocklesby semi scratch build
« Reply #153 on: December 14, 2015, 04:44:50 PM »

Thanks for your kind comments guys, the derek base mould was cured this morning, so I got the first castings done this afternoon, it's always gratifying when the first castings of an item come out OK, and I made up the first cast base, also got the strd aft derek base done, this is bigger than the other three and as there is only one I'm not bothering to take a moulding, next will be the derek "arms" the two forward are the same, the two aft are different from the forward ones and each other, I'll make them all out of styrene sheet, that I've just noticed I've nearly run out of.
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davidm1945

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Re: HMS Brocklesby semi scratch build
« Reply #154 on: December 14, 2015, 06:19:02 PM »

Derek = bloke's name.
Derrick = lifting device.


Pedant...moi?  Never... ok2

Brilliant build though!


Dave.
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radiojoe

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Re: HMS Brocklesby semi scratch build
« Reply #155 on: December 14, 2015, 06:40:04 PM »

I thought at the time, that didn't look right, I stand corrected  %%, I posted it on my old laptop that has been upgraded to Windows 10 since then the smileys and the spell checker don't work.
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Capt Podge

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Re: HMS Brocklesby semi scratch build
« Reply #156 on: December 14, 2015, 09:39:59 PM »

upgraded to Windows 10 since then the smileys and the spell checker don't work.

...and they call it progress <*<
 
Still, one day soon my XP aint gonna work no more. <:(
 
Excellent bit of work on the derricks there Joe. :-))
 
Regards,
 
Ray.
 
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derekwarner

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Re: HMS Brocklesby semi scratch build
« Reply #157 on: December 15, 2015, 12:14:52 AM »

That's OK Joe......I have been called worse {-)

One interesting point in the design of the luffing hydraulics of the ships hoists is the positioning of the cylinder [I did check the WIKI images to ensure the mounting was drawn correctly]

The mounting terminology is MT4, however with the trunion on the headcap.....the unusual point is that the cylinder rod clevis is fixed to the derrick structure and the cylinder inverted

So when pressure is applied to the rod side the boom raises...and all this sounds normal....however with a standard 2:1 ratio cylinder, the actual lifting/luffing force is effectively 1/2 of the lowering force

Now we could think that some dingbat designer got his raising & lowering efforts upside down......but no...there is a valid reason for all of this  O0....... any guesses?..............Derek
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Derek Warner

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ballastanksian

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Re: HMS Brocklesby semi scratch build
« Reply #158 on: December 15, 2015, 09:09:04 AM »

Does the extra pressure in the cylinder descending provide better control of the descent? You are a marvel with your resin casting. Many small wargames companies would love to get castings this crisp.

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derekwarner

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Re: HMS Brocklesby semi scratch build
« Reply #159 on: December 15, 2015, 09:31:59 AM »

Ian......I will post an explanatory PM....so not to further snatch the thread from Joe.........Derek
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Derek Warner

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radiojoe

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Re: HMS Brocklesby semi scratch build
« Reply #160 on: December 15, 2015, 11:26:48 AM »

Hi Derek (hope I've spelt that right) %%  Looking at the tight radius geometry of the derricks it would appear that's the only way the cylinder could be mounted, I suppose it could be the other way round it the ram was mounted more parallel under the luffing arm, but that would make it liable to being struck by the whatever it was lifting, come to think of it tipper trucks/trailers have them mounted inverted, I'm not sure about any hydraulic advantages of mounting them this way, although the gas rams we fitted at work were always inverted apparently stops the seals drying out. :o
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derekwarner

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Re: HMS Brocklesby semi scratch build
« Reply #161 on: December 15, 2015, 11:44:19 AM »

Yes that me Joe ;)........again so as not to distract from your build thread, I will send the same PM to you as sent to Ian

It explains in relatively simple terms and concepts the basis behind the inverted cylinder mounting...which is interesting to me, but not at the expense of your build thread..........

I look forward to read & see the continuing build & images :-))........Derek
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Derek Warner

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Starspider

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Re: HMS Brocklesby semi scratch build
« Reply #162 on: December 15, 2015, 12:14:31 PM »

Very nice castings again Joe  :-))
Derek could I have the explanation as well please I can't think of a reason either  >>:-(


colin
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radiojoe

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Re: HMS Brocklesby semi scratch build
« Reply #163 on: December 17, 2015, 03:49:25 PM »

All the derrick bases done, and I've made one of the luffing jib turrets, a bit of a fiddly job so I'm going to try and cast them, quite an odd shape so not sure how they'll come out but we'll see.
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radiojoe

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Re: HMS Brocklesby semi scratch build
« Reply #164 on: December 18, 2015, 02:03:06 PM »

Cast the first jib turret this morning and have just got it out of the mould, a bit tricky to get it out but with some patience I got it out in one piece so it should be ok for three more, I'll carry on with the derricks when my order of styrene sheet arrives CMB are usually quite quick even at this time of the year.
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Starspider

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Re: HMS Brocklesby semi scratch build
« Reply #165 on: December 18, 2015, 03:28:32 PM »

Thats impressive Joe to get an item that complicated with no draft out of a one piece mould, deep respect.
I thought you would have had to venture into at least two or even a three part mould.  :-))


Colin
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Capt Podge

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Re: HMS Brocklesby semi scratch build
« Reply #166 on: December 18, 2015, 03:30:51 PM »

You've certainly got the knack there Joe - inspirational work. O0
 
Regards,
 
Ray.
 
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radiojoe

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Re: HMS Brocklesby semi scratch build
« Reply #167 on: December 18, 2015, 04:51:19 PM »

I thought it might be stronger moulded in one piece rather than two or three pieces glued together, as it has a long jib canter levered off of it, and although it would be fun to try and make the derricks moveable I doubt they would ever be used, so they will all be static and hopefully less prone to breakage. :o
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ballastanksian

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Re: HMS Brocklesby semi scratch build
« Reply #168 on: December 18, 2015, 09:14:59 PM »

As long as you are careful and don't yank the mould about then it will release the part. Joe is helped by there being round edges on the front thus there being less to catch and snag the mould.

You can slit a mould so that it opens like a crocodile's mouth, but you have to line the edges up properly so the casting isn't slipped. You will most often notice slippage or stepping at the mould parting line on white metal castings and there are a few reasons for this.

yet again Joe, your work looks top rate, well it is, there's no 'looks' about it.
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radiojoe

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Re: HMS Brocklesby semi scratch build
« Reply #169 on: December 19, 2015, 04:44:51 PM »

well here's my first attempt at a derrick, I've used a bit of modelers licence, well lets face it I've used a hell of a lot of licence, but this is my version roughly assembled, just another three to do.
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ballastanksian

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Re: HMS Brocklesby semi scratch build
« Reply #170 on: December 19, 2015, 06:53:14 PM »

Brilliant work Joe, that looks just the business!!!! I would make the next three at the same time to maximise on remembering dimentions etc unless you have boxed clever and have already cut all the components out?
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radiojoe

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Re: HMS Brocklesby semi scratch build
« Reply #171 on: December 19, 2015, 07:42:24 PM »

Thanks Ian, this one is one of the forward two the components for the other one are marked out, the aft two are different from the forward two and to each other, but now I've done one the rest should be easier. ok2
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SailorGreg

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Re: HMS Brocklesby semi scratch build
« Reply #172 on: December 19, 2015, 10:06:31 PM »

 :-)) :-)) :-))

radiojoe

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Re: HMS Brocklesby semi scratch build
« Reply #173 on: December 22, 2015, 04:39:38 PM »

Made the second forward derrick, and added a bit more detail to them, here their shown in position on the upper deck, next I'll make the two aft derricks these are both different, by the time I've done these I'll have all the running gear so I'll be cracking on with that.
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Starspider

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Re: HMS Brocklesby semi scratch build
« Reply #174 on: December 22, 2015, 05:55:19 PM »

very nice  :-))
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