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Metal Top Pantograph kit available


#1

moving over from Throwing my hat in the sled modification ring to try and keep things a little closer to sane there :slight_smile:

This is a kit of stainless steel pantograph arms to implement the triangular kinematics.

each kit includes:
2 vertical arms
2 #25 roller chain master links
2 #25 roller chain half links
4 horizontal arms
4 1/4" x 1.5" bolts
4 1/4" nylock nuts
2 1/4" x 3" lag screws
25 1/4" washers

I will be shipping priority mail.

$40 for the US
$55 for Canada/Mexico
$35+ shipping elsewhere

send the payment to david@lang.hm and be sure to include the address to ship the kit to in the comment on the payment or via a PM

The cad model for these is at https://cad.onshape.com/documents/e635c24e358635f51da4b399/w/5a63b67113542f248fbe6d7b/e/417e2805b04e08dc2064872c

I exported the dxf from sketch 2 and 4 and sent them to a lasercutting shop

I have made a template to help position this top pantograph - alignment drawing.zip (2.8 KB) that should simplify installation (the basic instructions below assume you do not have the paper template)

to use this kit, take one of the long arms and clamp it to the edge of a 7+inch piece of 2x4 (or 2x3 if that’s the right spacing for your weights). You want one hole close to the end, but it needs to still have strength, so ~1/2" from the end of the 2x4. The closer these holes are to the center line of the wood, the more accurate the next step will be. Then drill 1/4" holes through the metal about a 1/2" into the wood, and switch to a 5/32 or 3/16" drill and drill down as far as your drill will go to make the pilot hole for the lag screws.

Bolt the long arm onto the wood and flip it over so the metal is next to the sled. Put a pointed bit in the router (or a very small bit) and center that bit in the small hole in the arm. Mark where the wood attaches to the sled.

unbolt the metal arm and assemble the pantograph.

At this point there are two ways to do this.

The easy way is to position a long arm like a J and attach two short arms to the top of the long arm. Stack washer, long arm, washer, short arm, washer (and add a second washer if needed), nylock nut. You want things snug enough to not rattle, but loose enough to move freely.

Assemble a second set, but with the bolts facing down.

now assemble the center, arrange the to assemblies with the bolts facing towrds you and the Js facing out. using the lag screws, assemble washer, right horizontal arm, washer, left horizontal arm, washer onto the lag screw and attach into the wood.

Once you have done this for both horizontal arms, attach the hunk of 2x4 to the sled. If everything was centered on the 2x4 edge, you should be able to just attach it at the marks you made earlier (if the holes weren’t centered on the wood flipping it over will create some errors)

attach the chains to the tips of the Js with the included master links

The result should look like this (note the stacking order of the parts)


or

This has an offset of one chain from the other of 3/16"

If this bothers you, you can add additional washers and stack it differently. One one side make the end horizontal bar above the vertical and the middle one below, and on the other side reverse these. In the center, add washers to put 3/16 (+1 washer) between the horizontal arms that are on one lag screw. This will put the chains at exactly the same distance from the sled.


What is the plan for the new ring kits for existing users?
Linkage kits (enable triangular kinematics)
Questions for a potential buyer
Possible "Table Round" Sled
Alguien en España
#2

kits sent to
@Rafi
@bar
Scott Smith
@pillageTHENburn
Jason Frazier
@MeticulousMaynard

Interestingly, according to the USPS tracking,the first one to arrive will be the one that has to cross to the east coast.

I just put all the items into the box and used the default sealing,please let me know if this results in washers or anything else falling out of the boxes.


#3

Did you get my order?


#4

not in time to get it out earlier, but I did get it.


#5

by the way, this is exactly why I listed what I had sent out :slight_smile:


#6

No problem. For a nearly retired guy I spend way too much time working. :frowning:


#7

Kirk, your kit is on the way


#8

Well you weren’t kidding about the shipping time. My kit showed up today here in Boston, MA. I guess we both live close to USPS distribution centers or something.

I’ve been spending tonight trying to figure out how I want my sled to look with this new improvement. I’m aiming to cut an entirely new sled for this version, since I’ve been using the first sled I cut with the temporary version. Looking forward to a more final design. I’m also very curious to see the improvement in accuracy. Even in limited amount of time cutting I can see how this will help.

Question, if I wanted to replace the center washers with bronze ones to act as some sort of bushing, do Oilite bushing make any sense or are they simply overkill for this application?


#9

Well you weren’t kidding about the shipping time. My kit showed up today here
in Boston, MA. I guess we both live close to USPS distribution centers or
something.

I’ve been spending tonight trying to figure out how I want my sled to look
with this new improvement. I’m aiming to cut an entirely new sled for this
version, since I’ve been using the first sled I cut with the temporary
version. Looking forward to a more final design. I’m also very curious to see
the improvement in accuracy. Even in limited amount of time cutting I can see
how this will help.

if you are cutting a new sled, don’t cut the center hole out until after you
have everything else measured. you can put a nail through the small hole of the
arm to position things instead of the trick I described with a v-grouve bit.

Question, if I wanted to replace the center washers with bronze ones to act as
some sort of bushing, do Oilite bushing make any sense or are they simply
overkill for this application?

if it’s worth doing, it’s worth overdoing :slight_smile:

it won’t hurt.


#10

this morning I shipped out kits to Kirk and Justin Herman.

I have payments from
Matt Remine aka @Rancher (but no address that can find)
Michael Piechowski
Clint Loggins
I’ll try to get these out in the morning on my way to the train.


#11

@dlang, have you determined the calibration number for these linkages?


#12

it should be either 5.25" or 5.375" (133.35mm or 136.525mm)

David Lang


Is there a kinematics calibration guide?
Is there a kinematics calibration guide?
#13

Great, thanks :slightly_smiling_face:. The kit just arrived this afternoon, I’m cutting a sled for it now.


#14

pictures please (since I haven’t had a chance to do so. I’m in a meeting from 9am to 8pm tomorrow after 10-6 meetings today…


#15

I’m very interested in finding what the new calibration routine decides the
distance is :slight_smile:


#16

@dlang The kits in this batch are not per the modified design, correct? (i.e. hole is 0.26" not 0.25", etc…)?


#17

That is correct. I am running a drill through the small hole, so things fit
there (that may be a matter of the bur causing it to seem too small), but the
holes have a smidge of slop to them.

I think they are still far more accurate than stock, and I think it would be a
hard thing to determine the difference in accuracy between these and the wood
ones (especially after some time and wear), but the next batch (after I sell the
last half dozen) will be marginally better.


#18

I would describe the hole clearance as “Close”. There isn’t a lot of room for things to shift, which I honestly think is a good thing in this case.

Got mine installed last night on the machine. I haven’t cut anything yet, but just in moving the sled around I can see how this is going to improve my setup :smiley:

I’ll post a build log in the near future. @dlang Mayhaps I could supply some pictures for your build guide?

Short video showing my movement tests:

Yes, I did notice in reviewing the video that the left chain is twisted. I will be fixing that tonight.


#19

I welcome any pictures of the build process.

you used layers of plywood for the support instead of the edge of a 2x material, how high did you make your mount?

it looks like the master link is not pivoting cleanly on the left side, you may need to enlarge the hole slightly, or hit it with a file/sandpaper to make it just a smidge thiner. (or it could be the results of the chain twist)

is the right side doing the same thing?

while pivoting doesn’t matter most of the time, when you get into the bottom corners, there isn’t a lot of clearance between the chain and the metal, if they hit you will get a slight distortion, so it would probably be good to move the weights lower on the sled (just leave room for the dust hose)

what did you use for your bolts? (since you didn’t use what was in the kit)


#20

Mine came in the mail yesterday while I was at work (left at 5a, got home at 9p), haven’t yet had time to open and inventory it.

Ominously there’s a resealed by post office stamp on the box. Is the box supposed to rattle?