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Author Topic: Scale working crane: Flexi cable to mimic hydraulic ram?  (Read 1850 times)

npomeroy

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Scale working crane: Flexi cable to mimic hydraulic ram?
« on: December 02, 2020, 01:19:19 am »

I'm considering making a 1/32 scale tug with a working crane.
The  robotic cranes I see are quite bulky and not at all scale-like.  I'm wondering if one could make functioning rams that use flexible cable sliding in a tube.  Such cables are used sometimes in model aircraft where solid rods won't fit around curves.  The trouble is they are fine at pulling, but when pushing they tend to buckle the casing.  But consider a crane with "dummy" hydraulic rams: perhaps the ram rod could be pushed out by a flexible cable that went down into the hull where it was moved by a conventional servo.  The casing could be rigidly supported so shouldn't buckle.  As for managing the coordination, I'm happy with Arduino programming and I'm sure an interface could be worked out.


Has anyone seen or know of such a mechanism?


Cheers,
Nelson
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kinmel

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #1 on: December 02, 2020, 08:38:27 am »

This video shows home made working hydraulic rams.............    https://www.youtube.com/watch?v=klLI5skuwj4
Also search " micro hydraulic cylinders " for ready made rams
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warspite

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #2 on: December 02, 2020, 11:49:48 am »

Thats a great animation, its real micro rams thats needed, so what does the model excavator / truck community do at 1/24th scale.


I did think that the same idea as bicycle brake cable in a tube would do the same, though as it enters the hyraulic tube it would as suggested buckle under pushing as mentioned by npomeroy, but what if the hydraulic tube had a spring to keep the push rod out and the action of the brake cable was to pull the push rod into the cylinder, thereby when released the spring returns the push rod to where it started, no buckling in the hydraulic cylinder.


just a thought - maybe someone has built a working Hiab that could be eluded to how it was done.
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barriew

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #3 on: December 02, 2020, 01:15:24 pm »

It depends on relative sizes of cable and tube of course, but I successfully used this idea to simulate the ram on the ramp of my car ferry.





In this case the ram is purely a dummy, but the cable does exert its force through the tube with no buckling.


Barrie




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grendel

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #4 on: December 02, 2020, 05:29:02 pm »

in the meccano world a threaded inner is rotated by a small but powerful motor on the end of the ram extending and retracting the ram
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npomeroy

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #5 on: December 02, 2020, 10:44:11 pm »

Thanks for the various comments.  Is that video just an animation?  I couldn't follow all the explanation below. 
This video  https://www.youtube.com/watch?v=QRg0ZAvxVFk&ab_channel=TinC33 shows a working miniature hydraulic ram but it doesn't talk about the oil pump, which looks as though it would be too large/heavy to be practical inside a model boat.
If the Hydraulic cylinder was "solid" (i.e. so that the piston shaft was a snug fit) there shouldn't be much lateral space for a stranded wire cable to buckle.
The motive force for the cable could be a conventional servo like Barrie's example or a linear servo.  There are little ones made for Blade brand helicopters and these bigger more powerful ones  https://www.actuonix.com/L12-R-Linear-Servo-For-Radio-Control-p/l12-r.htm.  For a large scale crane these servos could possibly sit in place of a hydraulic ram.


I'm just speculating at the moment - no specific plan.  There would be multiple issues around ducting the cable if the crane also could rotate on a vertical axis as of course would be needed for any sort of practical realism.


PS - I see there are full scale model systems like this 1/14 scale buldozer https://www.rcnz.com/categories/construction-and-farming-rc/rc4wd-114-dxr2-hydraulic-rc-bulldozer/  so it may be possible provided it was a a large scale boat and one didn't skimp on the $$.


PPS - and here are the parts https://www.aliexpress.com/i/4001101569178.html?spm=2114.12057483.0.0.622a3c480fy9PI


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warspite

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #6 on: December 03, 2020, 10:08:46 am »

What I eluded to was as shown below - i was going to try and make two of these to pass through the deck of HMS Victory to operate the sails but the weight of all the bits and bobs would have made it top heavy (also I found an easier more hidden way).


As I first proposed, a cylinder inside of which is the pull rod connected eventually to one piece of the crane, the cylinder it sits in is attached to the other crane part, the rod has a bulge along its diameter - like you find on a ball point pen ink tube (it's where the idea came from), the spring is sat in the bottom of the cylinder and the cord or fishing line exits through the bottom say through a micro bore tube fitted to the end of the cylinder and the cord etc is attached to the end of the pull rod, as the cord is pulled out of the cylinder the pull rod is pulled into the cylinder, compressing the spring which cannot get past the bulge in the rod when the spring is completely compressed that's the end of travel, when the cord is released the spring returns the rod to the initial position, thereby there is no need to push the cable into the cylinder and it bunch up, the issue would be the pulling action on the cord transferring through the tubing to the servo, would it give - and just like on the real things some of the tubing could be small bore brass pipe to stop this happening, with hidden bends like shown below to the servo, after seeing the Type 42 parts made in 3D, could the bits be made in a printer with just the thread being added afterwards , just a thought
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npomeroy

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #7 on: January 14, 2021, 07:45:01 pm »

OK.  Belated thanks for that explanation.  Sorry I'm new to this forum and was accustomed to email notifications of replies, so overlooked the last post.
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Mike61

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #8 on: February 04, 2021, 08:56:05 pm »

Hi Guys
I'm a bit late to this party but I've been making a 1:32 pusher tug called Euro girl and I bought a 1:32 Atlas 5ton plastic non moving crane model non moving crane. I wanted to make it operate using a 2.4gHz transmitter/receiver via a couple of Picaxes & drivers. I also wanted the crane to look the same but was prepared to modify a bit - which I had to.

Arduino is a good controller and has come on very well in the world but I'm over 60 and feel its too late for me to learn C+.


Anyway as you have discussed its the small size, weight and motor torque that's the problem however, I've done it. It's a bit shakey and needs tweeking to rotate a full 180 degrees.

I used a 4 wire micro bi-polar stepper diameter 8mm length about 10mm for the end ram to extend/retract about 30mm, same motor to pivot the arm up /down.
A 12mm linear geared motor is used in the main arm ram to extend/retract about 50mm.
A continuous uni-polar servo motor to raise and lower the whole beams and another stepper motor (28BYJ-48).

I attached the motor shafts to a 2.5mm threaded rod which I embedded into a rectangle dowel piece with a hollow inside and nut glued inside them. The rod can't rotate so the 2.5mm rod simply rotates and pushes the dowel up and down the arms.

Was all this fiddly - you betcha! not to mention the software I had to learn and right.
It's fitted to a removable rear decking piece so I can swap it if its raining or rough water - its not water proof.

If anyone would like more info please let me know on this thread.
Regards
Mike
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npomeroy

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #9 on: February 04, 2021, 10:08:43 pm »

Thanks for that Mike.
Yes Arduino is a step up in complexity - I'm in the same age range and was using Picaxe for years but fortunately I had some direct help learning Arduino.
I'd be interested in seeing any photos or diagrams, although your explanation makes sense.  Also, any links or part numbers for the motors. 
Cheers
Nelson
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Mike61

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #10 on: February 06, 2021, 12:26:40 pm »

Thanks Nelson
Yes I'll send some data hopefully later today or tomorrow. Well done for getting practical support it helps you get up the ladder.
Mike
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Mike61

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #11 on: February 06, 2021, 09:30:36 pm »

Hi Nelson
Tonight I typed some info for you then when I attached some files and sent I lost the whole page so I'll send some tomorrow. just a case of getting to grips with mayhems site
regards
mike
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derekwarner

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #12 on: February 06, 2021, 10:12:42 pm »

Sometimes Mike, anything longer than haff a dozen lines, type it out on Word or Outlook, O0  then save & copy & paste back into MBM


We've all been there.......typed a page & a bit only to have a Server timer or whatever drop out & the content lost {:-{


Derek
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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #13 on: February 07, 2021, 01:45:08 pm »

Hi Nelson and Derek
Here is some info. I've put it into word then also saved a pdf to reduce memory size. It's three files - here goes.
Mike
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Mike61

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #14 on: February 07, 2021, 01:46:05 pm »

only one tx'd
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Mike61

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #15 on: February 07, 2021, 01:47:10 pm »

Hi last one
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npomeroy

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #16 on: February 07, 2021, 06:41:52 pm »

Many thanks Mike for the comprehensive report/data!
cheers
Nelson
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derekwarner

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #17 on: February 07, 2021, 10:26:28 pm »

Wow Mike ... a model within a model...... :-))


I think I understand the various motions, but unsure of the 4th motion as shown here


From the pedestal
1. = Slew
2. = Luff
3. = Extend/retract Box Arm 1
4. = ?? as shown in the image with the RED arrow...[it's opening and closing an Arc of motion but unsure of the Term]
5. = Extend /retract Box Arm 2


...and is that a wire hoist/lower drum located just below the Extend/retract 1 first Box Arm casing?


Derek
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david48

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #18 on: February 08, 2021, 12:35:21 am »

Action 4  is Dipper arm  with telly in or out action just same as hydraulic excavator
David
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derekwarner

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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #19 on: February 08, 2021, 06:52:33 am »

OK & thanks David...........'Dipper'

So Mike, .......

1 = semi rotary linear [stepper motor]
2, 3 & 5 = purely linear [extend/retract]
4 = semi rotary linear, but how is this Dipper driven?


Derek



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Re: Scale working crane: Flexi cable to mimic hydraulic ram?
« Reply #20 on: July 06, 2021, 10:07:35 pm »

Hi Derek
So sorry not to reply to your question, drifted off mayhem somewhat.
To move the dipper there is a micro stepper in the end of the first ram held in place with a wire twisted around the stepper. The two wire ends poke through holes in the plastic so that the stepper can tilt on this axis. The stepper shaft is connected by a 2mm sleeve to 2.5 threaded rod. Sleeve is tight enough and bends as the dipper dips up & down.


It has been very tricky at 1.32 scale, 1.16th, 1.12th would make life easier.
I now use a larger stepper under at the base of the crane to rotate it about 180 degrees. Being a plastic model it does shake a bit, I'll need to beef this up a bit.
Regards and apologies for very late reply.
Mike
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