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Homemade Arm...For all who said it couldn't be done...


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#1 Charles King

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Posted 27 October 2004 - 01:24 PM

check out this homebuilt stabilizer arm out. It was built by Andreas a member on the HBS website. Congrats to him for proving it is possible with determination:

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#2 AndreasKielb

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Posted 28 October 2004 - 04:53 PM

Thanks for the the nice words about my arm but most of all for putting the HBS site up :) ! The forum is a bunch of information and there are damn fine contributors with very nice rigs and ideas. Definitely worth a look in my humble opinion.

What makes homebuilding (or better custom building) difficult is that some high-tech materials are hard to find, especially in odd lots. That's why I'm using steel springs at the moment. But if anybody here has a set of titanium beta-c springs in the garage or knows a good place to buy them that would be great :D .

cheers,
Andreas Kielb
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#3 RobVanGelder

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Posted 28 October 2004 - 08:29 PM

Andreas, congratulations!

You must be a very good machinist and have the tools and machines available as it looks really well finished.

It could be a serious offer in the light-weight (DV-video) market.... :)
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#4 Charles King

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Posted 28 October 2004 - 11:47 PM

It could be a serious offer in the light-weight (DV-video) market.... :)

<{POST_SNAPBACK}>


Lightweight?! You can put a 16mm camera on that think, even a 35mm. Don't underestimate just by looking :)
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#5 AndreasKielb

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Posted 29 October 2004 - 12:06 AM

Thanks Rob, all the parts are machined from scratch and for little money by a CNC workshop. But I've a desktop mill and lathe at home that helped very well to reduce the costs additionally. The materials (titanium and 7075 alloy) where quite expensive though.

The weight range of the arm is supposed to be in the provid or efp area but I need to make plugs for the stronger spring set before I know exactly.

Andreas
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#6 Brad Grimmett

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Posted 29 October 2004 - 12:58 AM

How much did you spend building that arm?
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#7 AndreasKielb

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Posted 29 October 2004 - 04:06 AM

I spent almost 1500 Euros on material and labour, of course without calculating my own time, but I think it was worth the investment.

Andreas
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#8 RobVanGelder

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Posted 29 October 2004 - 11:06 AM

Lightweight?! You can put a 16mm camera on that think, even a 35mm. Don't underestimate just by looking :)

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Charles, I am sure that this arm is initially strong enough, but on the long run too?

There is one concern here, if I look at the hinges and their connection to the spring-elements: they are probably not strong enough in a real working situation.
Why? The way the arm in displayed right now is perfect for all parts, strong enough when they all line up straight.. But that´s not the working situation. Than the arm sections will be angled towards eachother in the range of 90 to 15 degrees, so you fold them together.
And this causes the greatest stress in all hinges, axles and their bearings.
It´s precisely for this that the professional manufactures have a triangle-like shape at the end of each spring-section, that is much stronger and divides the forces.
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#9 Charles King

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Posted 29 October 2004 - 11:40 AM

Charles, I am sure that this arm is initially strong enough, but on the long run too?
And this causes the greatest stress in all hinges, axles and their bearings.
It´s precisely for this that the professional manufactures have a triangle-like shape at the end of each spring-section, that is much stronger and divides the forces.


I understand what you mean. Now, are you reffering to the scissor-like brackets that connect both fore and aft arms together? If you mean this than it can't be because not even the steadicam systems have this. If not further explain. Better yet a pic will suffice. Thank you.
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#10 AndreasKielb

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Posted 30 October 2004 - 08:59 AM

Hi Rob, I think I know what you are referring to. The shape of my bones' squared-off ends are not as triangle-like as for example the Baer-bel arm.

Baer-bel arm picture on steadicenter

Compared with this arm my end parts seem quite short - somehow compressed. For my feeling this compact structure is especially well prepared for high torsion forces because the lever is lower. Of course that might be wrong but at least the walls are thick as hell and the axial bearings are very strong. They have dyn. load capacity of 3,32 kN.

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However, I ain't gonna fly a 35mm camera. My sled is a used SK2 so I'll stick around lightweight video or 16mm cameras like I would do with a provid.

Andreas
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#11 RobVanGelder

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Posted 30 October 2004 - 10:28 AM

Andreas, once again, congratulations on the fine workmanship! The detail picture shows that very well.

Yes, most manufacturers choose to have the spring elements inside the hinges, while you have made the hinge inside the spring element. Now you have one, problably wide bearing or 2 smaller close to each other and the professional arms have them spaced out more, on either side of the spring and that could be a stronger solution with side forces that can twist and torque the whole arm.

But your construction seems very strong, indeed. Put it through a test, we could all be surprised.

What does your arm weight at this moment?
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#12 AndreasKielb

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Posted 31 October 2004 - 05:23 AM

Now you have one, problably wide bearing or 2 smaller close to each other and the professional arms have them spaced out more, on either side of the spring and that could be a stronger solution with side forces that can twist and torque the whole arm.



Actually there are four bearings per axle. Two needle roller bearings for radial and two axial bearings especially for torque forces. AFAIK this is the common solution for arms which have the hinges inside the spring elements like GPI, Baer-Bel or ProGear.

The arm weights 6 kg but doesn't feel too heavy using it. Since it is finished I practice as often as I can with my small DV-Cam and a 7kg steel plate to increase inertia. I can try to make a small clip the next days :).

Thanks,
Andreas
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#13 Charles King

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Posted 31 October 2004 - 05:52 AM

Again Adreas, I'm proud of your work. :D


Now you have one, problably wide bearing or 2 smaller close to each other and the professional arms have them spaced out more, on either side of the spring and that could be a stronger solution with side forces that can twist and torque the whole arm.


Actually there are four bearings per axle. Two needle roller bearings for radial and two axial bearings especially for torque forces. AFAIK this is the common solution for arms which have the hinges inside the spring elements like GPI, Baer-Bel or ProGear.

The arm weights 6 kg but doesn't feel too heavy using it. Since it is finished I practice as often as I can with my small DV-Cam and a 7kg steel plate to increase inertia. I can try to make a small clip the next days :).

Thanks,
Andreas

<{POST_SNAPBACK}>


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#14 Marc_Abernathy

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Posted 31 October 2004 - 01:40 PM

beautiful arm!
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#15 AndreasKielb

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Posted 07 November 2004 - 08:48 AM

Thank you very much for the kind comments! In the meantime I finished and tested the stronger springs. With them the arm can handle an overall weight of 19kg very smooth and without any signs of deflection. If I use my sled with two batteries it'll possible to fly cameras up to 13 kg which is definitely enough for me :).

cheers,
Andreas
(... who continues walking the line now :D )
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