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  #1  
Old Thu 15 May 2008, 00:36
dmoore
Just call me:
 
Mamba 6-Roller Z Slide with a gas spring not fully retracting...due to build mistakes

dmoore made some mistakes - so this thread has been closed and archived

I think there was a discussion on this subject but I can't seem to find it now...

I have built the 250mm Z-Slide with the extended 6-roller slide and the 11" rack. I've used the McMaster gas shock, part number 9416K18 which has the following specs:

18.22" fully extended length
10.35" fully compressed length
7.87" stoke
.75" OD

With the 9416K18 shock, the Z slide works fine - it retacts within about 1" of the bottom of the lowest set of rollers (the first photo). The issue is that it's about 3.5" short of rolling up to the middle set of rollers (third photo - shows the shock with nut removed allowing full positive Z).

It doesn't appear that by just using a longer shock it will work because the body would then be longer (currently ~10"), not allowing full negative Z (second photo shows at full negative Z position).

So the solution seems to either be a lengthing of the tube and a longer overall shock or a spring. Any thoughts or other solutions?
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  #2  
Old Thu 15 May 2008, 10:25
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
David,
I am in the same boat right now.
I have done a mockup that makes the top mount vertically longer (higher z than the tube will allow) for a long shock that allows for longer stroke but allows for the compression stroke to work as well.
Your assumptions seem to be in line with what I found:
- Need taller mount to tube
- need longer shock.

But for now, my usable 7" stroke is working exceptionally well on my table with 8" side channels and a 1.25" of spoilboard. (which gives a net stroke of about 6.75")

sean
  #3  
Old Fri 16 May 2008, 12:43
dmoore
Just call me:
 
Quote:
Originally Posted by smreish View Post
But for now, my usable 7" stroke is working exceptionally well on my table with 8" side channels and a 1.25" of spoilboard. (which gives a net stroke of about 6.75")
I completely agree that more nearly all situations that the ability to have the slide pull up into the middle rollers isn't neccessary. Imagine the following -

6" of stroke from the spoilboard to the bottom of the collet
3" cutter, with about 3/4" in the collet (2 1/4" sticking out)
This results in a net stroke of 3 3/4" from the spoil board to the tip of the cutter

Now, you need to cut a 3D part out of 4" tall foam and you need to reach 3 inches into the part - which it will not be able to do.

Also having the z-slide pulled up into the middle set of rollers would better protect a bit in the router while loading or unloading the table. The bit would (assuming the Z was fully retracted) also be less likely to catch you if you were grabing something off the table.

In the future I will be cutting blocks of PS foam in "slices" to build a new shell for an art car. By having the highest possible Z, I can limit the number of slices required (the total height will be about 10ft) by using the thickest section of PS foam possible.

I am going to order the McMaster-Carr 9416K2 (22.36" total length) and then extend the 1x2 support tube. I'll report back later....
  #4  
Old Sat 17 May 2008, 01:43
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
While this is being investigated, suggest that the 1x2 tube be left longer and cut to length after mounting the spring. Somebody can add a note to drawing corrections thread please. (this Norwegian keyboard is a bit difficult . . . . )
  #5  
Old Tue 20 May 2008, 00:46
dmoore
Just call me:
 
9416K2 is the magic number

I received the McMaster part number 9416K2 Gas Shock and I am happy to say that it's a nearly perfect fit. You need to move the two shock mount brackets up 7/8" of an inch (center line to center line) from their current location. The only very minor issue is that it prevents (on the 250mm slide) the Z from retracting to the absolute bottom by 1/4" (which on my machine means the collet is nearly into the spoil board). It now pulls up out of the bottom set of rollers and into the middle set of rollers.

So, I would recommend purchasing McMaster part 9416K2 if you will be using the 6-roller slide. If you are obmitting the middle rollers in the slide, the correct McMaster part number is 9416K18. Also note that the bracket will need to be moved up 7/8" - so your overall cut length of the support (1x2" rect tube - drawing 10 40 364 S) should be extended by atleast 7/8" on the top.

Here are the specs for the 6-roller shock: 9416K2
  • 22.36" fully extended length (bottom of threads to bottom of threads)
  • 12.52" fully compressed length
  • 9.84" stroke
  • .75" Body Outer Diameter

I'll see if I can get some photos later.
  #6  
Old Thu 05 June 2008, 11:46
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by Gerald D View Post
While this is being investigated, suggest that the 1x2 tube be left longer and cut to length after mounting the spring. Somebody can add a note to drawing corrections thread please. (this Norwegian keyboard is a bit difficult . . . . )
Nobody added a note to the drawings corrections thread?

Pure luck that I remembered this issue . . . . .
  #7  
Old Thu 05 June 2008, 13:11
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
David, the assembly drawing of the slide correctly says what the length of the spring should be, so I can't understand the need for most of the content of this thread. The McMaster part number 9416K2 was suggested in the relevant thread long ago.

I have a suspicion that your 7/8" tube extension might not be essential either, but I think it will be good to add notes to the tube drawings to warn future builders that they might have to adjust the top bracket location depending on their source of a suitable spring.
  #8  
Old Thu 05 June 2008, 15:20
dmoore
Just call me:
 
Quote:
Originally Posted by Gerald D View Post
Nobody added a note to the drawings corrections thread?

Pure luck that I remembered this issue . . . . .
I was going to post a photo and a little more detail once I had used the new shock before I commited to anything that might be wrong. I will take some photos and accurate measurements tonight and post them.
  #9  
Old Thu 05 June 2008, 15:38
dmoore
Just call me:
 
Quote:
Originally Posted by Gerald D View Post
David, the assembly drawing of the slide correctly says what the length of the spring should be, so I can't understand the need for most of the content of this thread. The McMaster part number 9416K2 was suggested in the relevant thread long ago.
You are correct - It appears I order from this thread which lists the invalid part number:

http://www.mechmate.com/forums/showt...18&postcount=1 (not archived)

There are references of the correct shock (9416K2) spread throughout different threads:

http://www.mechmate.com/forums/showt...7&postcount=56

http://www.mechmate.com/forums/showt...14&postcount=1

http://www.mechmate.com/forums/showt...3&postcount=11


Quote:
Originally Posted by Gerald D View Post
I have a suspicion that your 7/8" tube extension might not be essential either, but I think it will be good to add notes to the tube drawings to warn future builders that they might have to adjust the top bracket location depending on their source of a suitable spring.
Again, you are correct - it is not /essential/. Adding the 7/8" extension gives you an extra +7/8" of Z, if there isn't a need for the extra 7/8", it seems fine to use the existing mount holes (though this somewhat defeats the purpose of the second set of rollers.) I also moved it as I had already drilled the stopper bolts in the back of the Z tube at their "max" point and without extending the tube and mount, when it "topped out" on Z, it would have hit the shock, not the bolt.

Quote:
Originally Posted by Gerald D View Post
David, the assembly drawing of the slide correctly says what the length of the spring should be, so I can't understand the need for most of the content of this thread.
You are correct - this thread is redundant. It might be also good to cut down: http://www.mechmate.com/forums/showthread.php?p=4818 and just replace it with the spring and shock part numbers for the 250mm slide. I have the updated part number in my master BOM now.
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