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Author Topic: Caldercraft Northlight Puffer with working Derrick Crane  (Read 84707 times)

Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #25 on: October 07, 2009, 10:37:28 AM »

Martin

Thanks for your comment - I hadn't realized that Photobucket displays more than the selected video!

I'm surprized that you thought you would need a boom that heavy! Did you get anywhere with lateral movement?

Regards,
            Mike
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Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #26 on: October 07, 2009, 10:47:36 AM »

Tigertiger

Many thanks for your thought - but I did try using a long length of thin elastic below deck (like my lateral movement tensioning arrangement) but it was still too strong to allow the boom to decsend without the double-block thread kinking. (See Martin's thought about using solid steel for the boom!)

Mike
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Bunkerbarge

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #27 on: October 07, 2009, 10:50:41 AM »

Gents, just a big word of warning here.  If you incorporate a working derrick in your model and use any form of weight to tension the boom when you operate the lift the effective weight will be instantly transferred from the point of which it is at rest on the model to the end of the derrick.  If the derrick is elevated this could have an immediate and disastrous effect on stability and the model could turn over.

This has even happened in real life so make sure that you do plenty of stability experiments in the bath long before you commit to putting this model on the lake and lifting the derrick!!
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derekwarner

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #28 on: October 07, 2009, 10:57:40 AM »

Corposant....you could consider resting the end of the boom in a crouch

The attached rough sketch should suffice... essentially...the 1/4" OD solid brass boom locks down to a crouch made from 1/4" OD ....K&S brass metal tube ....but with a 200 degree mouth.........& so it acts as a spring loaded holding device ....Derek :-))
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Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #29 on: October 07, 2009, 11:00:43 AM »

Roger

Beeswax sounds just the job - provided it doesn't cause the thread to become sticky. I'll certainly be giving it a try! I've tried spraying it with "dry-film" PTFE without success. I had wondered if it would be possible to "flame" it but realized that, at the speed I move at, I'd have no chance - the whole lot would go up in smoke!

Mike
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Bunkerbarge

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #30 on: October 07, 2009, 11:02:10 AM »

Just to illustrate the effect check this out:

http://www.albanyaerialphotos.com/stellamare.htm
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tigertiger

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #31 on: October 07, 2009, 11:05:33 AM »

Again, thinking out of the box.

You say the line will not run through the pulleys.
Have tried using Dynema, or even Dacron cord.

Both smooth and used in sailing. Very flexible, and Dyneema is smaller diameter (for a given strength) and slippery.
Both come in white, but dacron stains easily with boot polish, I imagine wood dye as well. I have not tried to dye Dynemma.

As for the elastic being too strong.
What if only a short section below deck was elasticated. This would reduce the pull.
Or you could try what the sailing boys do to maintain tension on winch drums. Where a ring on a piece of elastic is used to pull on the line and maintain tension.
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HS93 (RIP)

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #32 on: October 07, 2009, 11:19:38 AM »

can you put an extra loop in and use a pully block wirh a very light spring to tension.

peter
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Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #33 on: October 07, 2009, 11:36:38 AM »

Bunkerbarge

Thanks for the warning - and the illustration! I am hoping that 10g in the end of the boom won't cause much of a problem - lifting a load will be a different matter!

According to SWMBO, it won't be a problem for me as I'm not going to live long enough to finish the model!

Mike
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Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #34 on: October 07, 2009, 11:42:43 AM »

Derek

Thanks for your suggestion. The model comes with a white metal cradle for the boom, which sits on the edge of the deckhouse. I'm not sure I quite follow you on the "spring loaded" bit.

Mike
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Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #35 on: October 07, 2009, 11:59:41 AM »

Tigertiger

Your box is obviously a source of really useful thoughts! I was hoping someone would suggest something better than "Mercerised" cotton - "Dynema" or "Dacron" would appear to be just what I'm looking for.

Your thought about tensioning has made me realize I went off on the wrong track with my arrangement, so many thanks for that - a major re-think on the way!

Mike
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HS93 (RIP)

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #36 on: October 07, 2009, 12:00:54 PM »

it was for the secondry line   very rough sketch

peter
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Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #37 on: October 07, 2009, 12:11:01 PM »

Peter

Your suggestion (like that of Tigertiger) has shown me the benefit of posting ones faltering attempts on this forum! The puffer is my first build, so I'm on a steep learning curve. I should have paid more attention to the sailing fraternity!

Many thanks,
                  Mike
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Martin [Admin]

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #38 on: October 07, 2009, 12:30:38 PM »

Topic name changed....  :-)
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Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #39 on: October 07, 2009, 01:57:29 PM »

Peter

Re: your "secondary line" drawing. If the boom is lowered from nearly vertical, almost 30cm of the secondary line has to be "lost" below deck. I found it impossible to maintain a gentle enough tension on the thread within the available space. Thanks for your deliberation!

Mike
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Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #40 on: October 07, 2009, 02:10:59 PM »

Tigertiger

I've been exercising my limited number of little grey cells and my memory has clicked in. I did, in fact, start along the lines of your sail winch principle. My assumption was that the loop of thread for the lateral movement lines would be almost constant in length - which would have meant that your idea would work. This held true until I started to raise the boom! The loop then varies in length by a lot - hence the ungainly arrangement below deck.

Mike
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HS93 (RIP)

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #41 on: October 07, 2009, 02:21:30 PM »

you could do this and even use another spring on the single pully they only have to be very very light or elastic.

Peter
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tigertiger

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #42 on: October 07, 2009, 02:41:37 PM »

I believe Dyneema (aka Spectra) is used for fishing line. So you should be able to get some very small diameters.
I know that 30kg Dyneema is about 0.5mm diameter. This may be a bit big for you.

But I have googled spectra down to about 10lbs BS and 0.02"
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Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #43 on: October 07, 2009, 02:59:07 PM »

Peter

I'll give it a whirl! Thanks for not giving up on me!

Mike
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Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #44 on: October 07, 2009, 03:01:27 PM »

Tigertiger

Thanks for the info - I'll have scout around.

Mike
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Ron1

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #45 on: October 07, 2009, 11:12:09 PM »

Heres the mast and working winch on my son,s Moonlight,
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Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #46 on: October 08, 2009, 10:34:36 AM »

Ron

What a brilliant model - something for me to aim at! In my (very feeble!) defence, I am working at 1:32 scale rather than 1:24 and raising and lowering the boom.

If anyone wants to see how to do the job properly, have a look at www.north-cheshire-marine.org.uk/mn.htm

Many thanks for that,
                              Mike
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Corposant

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #47 on: October 10, 2009, 06:06:33 PM »

Peter (HS93)

It works! O me of little faith! Many thanks for your wisdom (and Tigertiger's "box").

As can be seen from the pictures and video, the experiment was very much a "lash up".







The weight on the boom weighed 9g.

By the way, is this picture any help?!



The plastic gears were a fortuitous find in Maplins (who no stock them - but they can be obtained from Como Drills www.mfacomodrills.com - who also supplied the motor).

Mike
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HS93 (RIP)

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #48 on: October 10, 2009, 08:35:39 PM »

glad t worked , if you make a double block two sheaves( think thats what they are called ) it may make it a bit smaller and simpler.

Peter
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HS93 (RIP)

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Re: Working Puffer Derrick crane anyone?!?!?
« Reply #49 on: October 10, 2009, 10:50:03 PM »

if you did it this way with a double version of your blocks.

peter
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