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Metal Top Pantograph kit available


#101

David, I made an alternate version of the Fusion 360 model of the top mount system based on your onshape model:

http://a360.co/2CQXNQu

Is this the linkage kit you’re sending Gero? The horizontal arms look quite a bit larger than the one I have on my machine.

Gero is getting a kit like you have, just with 7" (hole-to-hole) horizontal arms
instead of 5" arms.

looking at the pricing, if I can get someone to cut this properly, it is close
enough to the same price to have longer arms that it’s not worth making two
versions of the kits.

I really like that center support. I may try to machine one of those myself,
it seems like it would make the assembly much stronger! :smiley:

As long as both sets of horizontal arms are anchored to the same piece of wood
(as opposed to pillars like your model showed), it’s pleanty strong enough and
the metal doesn’t improve it any.

But the pre-cut metal makes it so that there is no possibility of the holes
being in the wrong place (which would make the geometry of the arms not work),
and potentially simplifying the mounting.

If I do make these (and they continue to sell after the 'official ring mount’
becomes available), there will be extra center supports, so I will look at
sending them out to people who have the older version of the kit.

David Lang


#102

I think that this is a really really cool idea, and possibly will always be a better solution for large routers than the ring. Having the ring be small makes a big difference to how smoothly it rotates and if your kit can acomidate a large router easily and is simple to install it may always have an edge there.


#103

see logans post on why linkages should move smoother than rings (differences in
how the forces are applied to the joints vs the bearings)

can you PM me with who your metal fabricator is? I’d like to see if they can cut
this out (and at what cost). I suspect that the laser-cut metal can get down to
~$20/kit. Cutting them from aluminum and anodizing them would save considerably
on the cutting costs, and I think would end up with a smoother and harder
surface. In small quantities like I’ve been doing, it’s not cost effective, but
for a larger quantity, it could drive the cost down another $5 or so.

The special chain links can be eliminated if you can punch out one pin
on the chain [1](leaving the side plates rather than the center link at the end)
and use a smaller version of the spring pin that you already ship to go through
the holes on these side plates and the metal of the arms. This saves about
$4/kit compared to my costs.

This just leaves the washers and bolts, which get much cheaper in bulk (as
opposed to the local hardware store that I’ve been using :slight_smile: )

I’ve been using 1 1/4" bolts to give me sufficient smooth shoulder to have
things run on. Ideally, a 3/4" bolt with 3/8 smooth and 3/8 thread would be
cleaner. you could cut down the bolts, but that’s labor.

David Lang

[1] a manual tool to do this is something like
https://www.amazon.com/Koch-7725010-Roller-Chain-Breaker/dp/B004HKIU4C/ but it
should be trival to rig up a hydrolic tool (and your chain supplier may be able
to do this for you)


#104

The geometry of the end of the arm causes the pin to push the first link out of line at the extremes of range. I abandoned the ones I bought and made pins with more space between the ‘arms’ to solve this, along the lines of horse blanket pins.


#105

I was looking at that and wondering how much of problem this would really be in
practice.

if this is really a problem, we can create a notch on the back of the arm for
the pin to sit in so that it doesn’t get in the way of the chain.


#106

Something like that would be necessary if a different pin isn’t available.


#107

Hey Folks, I received the new top panto kit and would like to cut a new sled. I see that MeticulousMaynard has posted a .nc back in october. Has the dimensions changed since then or am I ok to use that? There so many sled files in circulation its hard to keep the versions strait.

Thanks!


#108

Hi @dlang,
Since I can not yet send PMs I am using this channel.
I have sent you an email regarding an order, have you received it?

Kind regards, Jeroen


#109

Welcome @jeecee!
A little reading, posting and likes will get you over that in a day, I guess.


#110

Yes the kits are available, I hadn’t had a chance to check shipping to Germany,
but it looks like it’s $35 (so a total kit price of $70)

As for time, the post office claims 6 days, but I’ve had customs take two weeks
before it left the US, so it could be a month or so.

I posted a topic a couple weeks ago about finding someone in the EU to put the
kits together, I need to dig up that topic and see if anyone is still working on
that.


#111

@dlang,

Have you been able to come up with a better connection/linkage method than the takeapart-chain link? I spent a good 45mins and lost 2-3 extra link parts just trying to dis-reconnect my sled this afternoon, it was a bit of a shitshow.

Admittedly I have giant fingers, but it seems like the metal linkage pantograph needs some quick connect/disconnect capability. I’ve experimented with various pins to but haven’t found anything that works particularly well yet.

if anyone has a solution for either a quick dis/re-connection of the chain to the metal pantograph or the pantograph to the sled, please share.

cheers.


#112

@mrfugu

I’ll start working on that soonish. Looking at how we might do quick connect / disconnect or part capture. I appreciate your candor.

@dlang
We should discuss this off line sometime soonish. Maybe if we both are at the meeting this weekend.

Thank you


#113

I’m going to attempt a ‘quick disconnect’ that leaves the pantograph on the chains but allows the sled to be detached while maintinaing tolerances on spacing. I’ve got some aluminum extrusions on the way and various connectors, hopefully i can get something together that’s relatively easy to use and make up a parts list from mcmaster-carr…

more as I have it.

(I swear the second any one of those chain link bits hit the ground in my garage they bounce into an alternate universe, gone forever!)


#114

Here’s my approach to a quik-release, a piece of 2mm music wire from the hardware store bent into a rudimentary safety pin.


It replaces the normal pin in the half-link. The picture angle is deceptive, the gap is just enough to slip past the linkage arm. Music wire is stiff stuff, too stiff to work like a real ‘safety-pin’.


#115

with the latest kits I’ve been sending out, there is a half link

that is drilled out to accept a hairpin like the ones used to hold the chain in
the original maslow (but slightly thinner)

that way you don’t have to mess with the clip of the master link after you have
it all assembled.

If you have a chain breaker, you can also punch out the pin from both sides to
leave the side plates attached, then drill that out to fit a pin.

David Lang


#116

Hi:

Just wondering if any of the metal pantograph’s are still available? I’d like to purchase one.

Thanks!
James


#117

are these better than the metal ring piece? sorry I forgot what it is officially called haha


#118

@thorne Please reach-out to @dlang , Yes they are available.

Thank you


#119

This is an opinion from someone who has not used either–I am using pillageTHENburn’s wooden linkage, and software issues have kept me from my first cut–but I think yes. The metal ring adjusts proportional to the cosine of the error angle, I haven’t worked out the math on the pantograph, but I’m sure it’s a stronger function of the angle, so it should adjust “better”.


#120

Seems like it would be much easier and cheaper for those in Europe to just use 1/2x3/16" metal bar. I have not done the math, but I’m pretty sure if one cuts the 4 horizontal pieces and drills them all together so the holes are in the same spot, (stacking the bars on a drill press vice would work) and does the same for the 3 vertical pieces then the resulting geometry will work fine. (Shorter vertical piece shifted to one end) after all all you are doing is making two identical rectangles. Even if your chain mounting hole if off a hole half inch you just move the mounting point to compensate.

so if the accuracy of a laser cutter is not needed (only the repeatability of drilling a few holes in same spot) and you take a few minutes to paint them you can use plain cheap carbon steel and drill one yourself for a few dollars.
And if you really want stainless steel you can do that too, the material will just cost 4x more. Nickel plated bar is also available but is probabaly hard to find for most. Any hardware store carries chain link fencing stiffness made of galvanized metal those are thinner but I’m guessing will work

Which brings up the last hurdle and that is the angled cut that is needed on the vertical bars so the chains can clear the bar when the sled is in the bottom corners. One can either make a short linkage piece 2.2" long in the drawing OR make the top motor mount bar 12’ long so the angle is not as severe.

It might even be cheaper to get these cnc machined than laser cut?. I’ve had bars cut and tapped before and it was not that expensive if done in bulk.

above drawing shows the blue outline of the standard bars over the laser cut bars. if one wants the file, pm me. they can pirnt this out to scale and just put paper over the bar and use a metal punch to get the holes drilled very precisely.

I would add unhealthy washers to keep friction very low on the joints as well