Identifying COG On Sled

I have a Bosch EVS router that is HEAVY and I see the parallelogram linkages on 2x4’s to raise them off the sled.

How do I figure out how far off the sled my linkages should be?

I believe the short answer is:

The goal is to have the chains from the motor to the sled parallel to the working surface.

The goal of the sled as I understand it is to be able to hold it in front of you and have it hang balanced.

FYI - My machine is working great but I ignored the norm and have my router ejecting dust at a 30 degree angle so my octagon shaped sled needed more weight on the left side. I did choose a 2x4 riser for a top pantograph kit from @dlang.

I believe @Gero might be able to chime in on heavy sleds.

Thank you

I believe the short answer is:

The goal is to have the chains from the motor to the sled parallel to the working surface.

The goal of the sled as I understand it is to be able to hold it in front of you and have it hang balanced.

re-order these two, first get the sled balanced, then make the chains parallel

I believe @Gero might be able to chime in on heavy sleds.

If the sled is too heavy, you will have trouble cutting along the top

How important is this? Should you set it up so that the cog never passes the connection points, or do you just make sure it’s balanced when the z-axis is in the middle?

With the bosch pof 1200 routers, there is significant weight moving up and down depending on where the z-axis is.

This post might be of interest:

As @dlang said, first you balance the sled, then adjust the motor mounts to keep the chains parallel to the sheet.

Ways to balance in order of how much the impact is on the sled tilt:

  1. hight of the mounting for your triangular kit
  2. weight below the router
  3. with the top mount kit you can mount the arms the chains attach to, either on top or down and with washers (spacers) you can fine tune in both directions.

My example for the approach (likely not the best way to do it):
Fist was A, a rock solid hardwood with screws, dowels and glue.
Screw and dowel holes in the sled an through the hardwood drilled with the same g-code on my desktop-cnc.

Second I used ‘wheels’ leftover from a lighting project to stack until I thought I have the height.

With this measurement I cut block B and again used the cnc to drill dowel and screw holes so it would fit on A. Maintaining the correct distance to the bit is crucial.
I ended up to high :frowning: so until I find a way to bring B down evenly, I mounted the ‘chain-armes’ from down and added bearings as spacers to lower more.

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My bosch 1615evs router might not work at all then, its HUGE and my chains would need to be over 11in off the plate for balance…

I have been trying to sell it and get the dewalt but not exactly the router market season yet.

That seems too high. Is that with bricks and the router at a depth assuming a bit to be halfway in the material? From pictures it does not seem bigger (more about similar) then my bosch GOF 2000 CE.

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Yours is the newer version of mine. The used a very heavy motor to get the 3.5HP rating. Maybe I need heavier bricks.

I found when the base moved the top edge of the base would bounce up and off the work surface.

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Replacing it is then the better option. It’s just a feeling, but I believe that I have explored the upper weight limits already and going more heavy will give issues at the top of the sheet trying to achieve acceptable feed-rates. Also the risk of burning the chips.
Neither your 3.5 nor my 2.7HP is needed (unless your planning to rip 2 sheets at the same time in one go). With a new sled 2.0 I will go the other extreme and go light. The Makita RT0701(1-1/4HP) will be on it.

Replacing it is then the better option. It’s just a feeling, but I believe that I have explored the upper weight limits already and going more heavy will give issues at the top of the sheet trying to achieve acceptable feed-rates. Also the risk of burning the chips.
Neither your 3.5 nor my 2.7HP is needed (unless your planning to rip 2 sheets at the same time in one go). With a new sled 2.0 I will go the other extreme and go light. The Makita RT0701(1-1/4HP) will be on it.

How important is this? Should you set it up so that the cog never passes the
connection points, or do you just make sure it’s balanced when the z-axis is
in the middle?

experimentation needed :slight_smile:

but people have been working with the COG wildly wrong without major problems,
so it’s probably not critical until you get near the edge.

I would err in having the chains on the high side

as long as your top beam moves out far enough to be balanced and your supports
are solid, there’s nothing wrong with the chains being high off the sled.

But once you factor the weight of the sled (and whatever bricks you have on it)
into it, I don’t think you will be that high. With the rigid 2.5HP router the
balance point is about 3" off the sled, I wouldn’t be surprised to see you get
to 6" or so, but 11" seems wrong.

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@dlang, from what I have seen I still believe the CGZ shifts depending how high the sled is on the sheet. At the top, the line drawn between the chain-mount-points is closer to the bit, giving a sled a more top-tilt.
If the sled is at the bottom, the chain-mount-points are near the top of the sled pushing the down part more to the sheet. This effect increases with rotation radius and with how heigh you need to mount your kit. I think @bar mentioned not so pretty results with a bigger ring.
With L-brackets we had a fixed point on the sled, so once balanced it would work everywhere on the sheet. With triangular you can only balance for one point, preferably the centre, to keep the opposite tilts equal to on up or down position.
I have tried heavy and high on Z and am determined to go as flat as possible for my sled 2.0

@dlang, from what I have seen I still believe the CGZ shifts depending how high the sled is on the sheet. At the top, the line drawn between the chain-mount-points is closer to the bit, giving a sled a more top-tilt.
If the sled is at the bottom, the chain-mount-points are near the top of the sled pushing the down part more to the sheet. This effect increases with rotation radius and with how heigh you need to mount your kit. I think @bar mentioned not so pretty results with a bigger ring.

If the chains are attached near the CGZ of the sled, there is almost no Z force
applied by the chains. can you please draw what you are talking aobut

With L-brackets we had a fixed point on the sled, so once balanced it would
work everywhere on the sheet. With triangular you can only balance for one
point, preferably the centre, to keep the opposite tilts equal to on up or
down position.

I don’t understand what you are talking about. The triangular kits keep the ends
of the chain at the same distance from the bit at all times, and with the forces
from the chain always directed at the bit. This is going to be far more stable
than the L brackets where the forces applied by the chains are in very different
directions depending on where you are on the workspace

I have tried heavy and high on Z and am determined to go as flat as possible for my sled 2.0

Heavy is bad, we know that. As long as the sled is balanced, the height of the
chain from the sled does not matter.

sorry for the late reply, got stuck on the method to make it more clear where I am drifting.

Sadly failed on the search for a fast tutorial using Blender Physics to create a sled with a tower sticking out of the middle hanging on ropes and changing the attachment of the rope in Y on the side view of the sled to find a difference in tilt.

Hope to follow up soon with an attempt in inkscape. At all times I do consider to be wrong.

The second option I will try is to cut two 2x4 in length to put under both chains so the sled does not touch the sheet. This I will do once with the sled at the top and again with the sled at the bottom (both cases X0). For L-brackets it will not change the tilt. With triangular I have doubts that I need to prove.

It took a moment, CGZ can’t be balanced for both (unachievable extreme) pictures of chain angles.

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CGZ would be in and out of the picture you just posted.I still don’t see ho the angle of the chains affects this.

as far as the forces of the chain in XY plane go, the force of the chain is directed at the bit, that is the effective point of support. and the point it pivots around.I don’t think that the bricks below the bit will cause it to pivot more when the chains are high than when they are low on the sled

I think he is trying to say the angle of the chains affects how easy the sled tips. chains at top more stable than chains at sides. for example lets say chains are attached below COG by mistake. top chains will work, side chains will cause tilt.

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