Sprung Kato GG1 pantographs

[rtroop]

Bryan, perhaps I’m misinterpreting something, but it looks as if in the design you are proposing the spring tension is applied between hooks formed by the extensions to the stop tab.  Since the spring tension is applied below the pivot holes it will have the effect of pulling the upper part of the arms apart which will lower the pantograph, not raise it.  Also I believe that for the equalizer bars to work they must be attached above the pivot holes on one arm and an equal amount below the pivot on the opposing arm. This is the arrangement used on all of the models I’ve looked at that are equalized.

[bbussey]

Bob,

Once the part is folded everywhere, the spring hooks are indeed above the pivot holes. 

Also, the mounting points for the equalizer bars are on opposing sides of the pivot (albeit barely) once the part is folded properly.  It's just difficult to see with the part flattened and the fold lines not identified.

[bbussey]

Here's the new panto with the equalizer holes moved a little farther out from the pivot center and diametrically opposed at nearly 45 degrees.  The fold lines have been added for clarification.  All folds are up.  The image on the left is the stock part.

[peteski]

Bryan,
I think that you still don't have the equalizers correct.  Study Bob's diagram from his earlier post. I'm also even more confused by the fact that your equalizer arms are to be bent - twice! They should be on the same plane as the arms.  Here is my take on the equalizer arms:



As you can see, no bends are needed. One is above and one below the bottom pivot. Only one etching is needed as the equalizers on each side are always opposite.  Without bends, the assembly is also stronger.

Looks like you are seriously considering making this a reality!  If you don't have one, I can send you one of my Arnold pantographs so you can  see first hand how the equalizers function.

[bbussey]

Your equalizer bar holes don't take into account the lack of clearance between the body and panto, so that's an issue.  The equalizer holes don't have to be on the same plane as the pivot hole, thus the double fold.  My equalizer holes also are opposing in relation to the pivot hole, just not as great a distance as yours.  The distance shouldn't matter, as long as the equalizer holes are opposing with the center of the pivot being the origin, and the distance of the equalizer hole centers and pivot hole center are greater than the radius of the pivot hole .  Regarding the double bends - they are necessary to avoid having to modify whatever host body the panto is installed on for additional clearance, in this case the GG1.  By etching out of stainless steel and matching the .30mm thickness of the brass original, it will be more than strong enough.

My goal is to have a functional panto that can be added to the host body without doing any work to the host body, thus the need for some creativity in the design.  The reason that Kato has the curved edges around the pivot holes is so the panto clears both the panto base and the host body while pivoting.

[peteski]

Bryan,
I have to admit that I have not actually looked at the Kato pantograph (I have to dig out my GG1 to get a better look).  As far as the distance between the pivot and the equalizer holes goes, it matters quite a bit how far they are from the pivot!  If they are too close the tolerances get critical. The further they are from the pivot, them more stable the arms will be and even little slop in the linkages will not throw things off.

I guess that without actually looking at the pantograph I can't visualize your design.  But just at looking how close the equalizer holes are to the pivot holes, it will not be a very stable design (unless there is no slop at the linkages at all, which would be pretty hard to achieve).  I also encountered another pantograph with no equalizer linkage. Well, it uses linkage-less equalizer. I'll have to see if I can find the loco that had it.  But it might have been a Japanese-prototype H0 pantograph which I sold on eBay.

[bbussey]

I realize that, but there isn't a lot of room to play with.  The idea is to have the revised panto be a drop-in replacement without modifying the host model.  So tight tolerances it will be, with .010" diameter steel wire needed for the equalizer rods.  That's the way I design the freight cars, with tight tolerances, so no reason to stop now.   
 

[peteski]

Ok Bryan,  I guess I'll have to wait and see the results.  If it works - great!  If it doesn't - don't say that I didn't warn you that the equalizer holes were too close to the pivot points. 

I'm also curious how you will retain the 0.010" linkage rods. On factory made pantographs ends of those linkages are normally flattened by some sort of machine.  I also think that 0.010" wire is a bit too thin. But then again, I shall wait and see.  If I were in your position, I would not commit to production until I had a working proof of concept first, but again, you own a model manufacturing company while I just sit on my behind making comments (based on my experience and on "Peteski's logic"). 

[bbussey]

Ok Bryan,  I guess I'll have to wait and see the results.  If it works - great!  If it doesn't - don't say that I didn't warn you that the equalizer holes were too close to the pivot points. 

I'm also curious how you will retain the 0.010" linkage rods. On factory made pantographs ends of those linkages are normally flattened by some sort of machine.  I also think that 0.010" wire is a bit too thin. But then again, I shall wait and see.  If I were in your position, I would not commit to production until I had a working proof of concept first, but again, you own a model manufacturing company while I just sit on my behind making comments (based on my experience and on "Peteski's logic"). 

There's no room to move the equalizer holes outward without compromising the body (and the visuals),  so either they will work or they won't.  The equalizer rods would fit inside of the "U", which is what will hold them in.  Currently the plastic pivot post does not extend past the thickness of the etched metal, so that shouldn't interfere with having the equalizer rods inside.  Stainless steel wire of .010" diameter is very strong, especially at that short a distance.

Who said anything about production?  This will be one of those pet projects, of which the fabricated components will be made available to others if they desire.  But there's no way these could be manufactured and marketed at a price where they would sell and cover costs, let alone generate a profit.  The current non-operating pantos MSRP at $12 a pair currently.  If this could be marketed at $12 each, I'd be surprised.

[Chris333]

Can you get sheets pre-blackened at PPD? Or would you do that yourself.

[bbussey]

I'm not sure they do it on the stainless.  I'll have to check.

[sizemore]

You could "blue" it like a fire arm. Same process as blackening.

The S.

[peteski]

Looks like Bryan wants to re-do  the bottom arms of that pantograph. If he uses blue finish, it won't match the top pieces (which have brown/black finish).

[nkalanaga]

The best pans I've seen, and what I'm using, are from Overland, and a pair of them about doubled the value of a Kato electric.  Even those don't pick up power, but they do work mechanically, and could be used for pickup if they didn't have paint in all of the joints.  So, no, I doubt that a good looking, scale, operating pan could be sold for $12.  Ncat used to sell some that worked very nicely, for those who want to use them for pickup, but they looked clunky.  They cost more than $12 years ago.

[TrainCat2]

Bryan,

I am working on a MILW project that could benefit from these. I can throw these onto the thick brass side frame sheet for you if you don't mind a little wait while the rest of the project catches up.