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Z Axis-Support

RF-45 Clone Head support

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Neil Lickfold22/04/2019 10:56:34
556 forum posts
102 photos

So I added a 850N Gas strut to the left hand side of the X45 clone Z axis to make it easier to wind the head up and down.

Made a couple of brackets to attach the end of the strut. The Strut is just one from an Auto parts store. It is 10mm shaft and 765 mm long with a 480 mm compressed length. So is 285mm max stroke. I set the strut when the top of the casting was 10mm above column . Max I could easily wind the head to.

When I made the plates to hold the strut ends, I drilled the holes 5mm the tapping diameter of the M6 for the casting. Then used the plate as a pattern to drill and then tap the casting. Later drilled to 6mm on the drill press. To hold the strut, I tapped M6 and counter sunk the holes for the M6 screws to be flush on the under side of the plate. These were done up tight to create a stud for the strut to be attached to.

Neil

gas-strut.jpg

850n-gas-strut.jpg

lower-mount.jpg

pattern-drilling-for-m6tap.jpg

lower-plate-drilled-5mm.jpg

lower-bracket-fitted.jpg

Neil Lickfold22/04/2019 11:42:47
556 forum posts
102 photos

I just checked the spindle to table max height, and it is at the max the manual says it should be. So I am happy that I have not lost any height in the addition of the strut. It is no issue to wind up and down the head assembly now. It used to be a lothesome job by hand. May get all enthusiastic and add an electrical power feed to it next.

Neil

HOWARDT22/04/2019 13:19:24
426 forum posts
14 photos

It looks as you have the cylinder mounted with the rod up. Manufacturers recommend rod down so that the rod seal remains lubrcated.

Brian G22/04/2019 14:10:58
513 forum posts
11 photos
Posted by HOWARDT on 22/04/2019 13:19:24:

It looks as you have the cylinder mounted with the rod up. Manufacturers recommend rod down so that the rod seal remains lubrcated.

First thought was "But tailgate struts always have the cylinder down." followed a little later by the realisation that I only look in the tailgate when it is open enlightened

Brian

Jon22/04/2019 16:31:14
988 forum posts
46 photos

Good idea but i havent any room to do that on mine. Cables and Z axis dro in the way.
Its been 9 years since the transfer box broke on Super Lux and not paying £244 back then for the privilege minus motor.

Simon Williams 322/04/2019 17:05:10
399 forum posts
65 photos

I don't understand the force indicated on what I take to be the plastic wrapping for the strut in Nm? Am I missing something?

Rgds Simon

SillyOldDuffer22/04/2019 18:08:25
4536 forum posts
971 photos
Posted by Simon Williams 3 on 22/04/2019 17:05:10:

I don't understand the force indicated on what I take to be the plastic wrapping for the strut in Nm? Am I missing something?

Rgds Simon

Offered as a suggestion!

I think the force needed to operate the strut is given as a torque measurement because they're most commonly sold to support car tail-gates or boot lids.

gasstrut.jpg

The diagram shows a tail-gate applying a weight to a gas strut. More force would be applied to a strut mounted in the blue position than one mounted in the red position. So choosing the right strut depends on the weight of the tailgate and the struts position along its length. As the tail-gate is hinged, a turning force is applied to the strut and, like a torque wrench, it's expressed in Newton metres.

I won't attempt the maths needed to translate 850Nm torque into the equivalent weight of an up down milling head. My maths is terrible at the best of times and I've got hay fever. 85 Newtons is roughly 85kgf, or 190lbf.

Dave

Simon Williams 322/04/2019 20:29:33
399 forum posts
65 photos

SOD - Dave - thanks for the explanation, but it still doesn't wash. There is no torque applied to the strut, only a force acting to compress it. The strut of course provides a force reaction to this compression; the magnitude of this force can be measured in Newtons, lbf, Kg (wrongly, but at least it's understood), poundals (if we must) etc. etc. All are dimensions of force, not torque.

Maybe it's just a typo. (Occam's razor!)

Thanks as always

Simon

Neil Lickfold22/04/2019 22:22:22
556 forum posts
102 photos
Posted by HOWARDT on 22/04/2019 13:19:24:

It looks as you have the cylinder mounted with the rod up. Manufacturers recommend rod down so that the rod seal remains lubrcated.

Thanks Howardt, Ill change it then. It's no deal to wind to the free length and to remove the Strut. I did not think about the oil inside keeping the seal wet/lubricated.

Neil Lickfold22/04/2019 22:27:37
556 forum posts
102 photos

The photo of the tag is for the part number reference if any one else would like t make a similar support.

I think the people in China who made the strut used Nm instead of N for the strength of the gas spring. Not sure if that is the max strength it has or the force required to move it. I weigh 74 kg and that was not enough to make it move.

Frances IoM22/04/2019 23:01:00
623 forum posts
22 photos
I recall an earlier thread about using a 120N gas strut for a X1 Mill head - that head weighs something around 12kg I think.thus an 850N strut would appear to support 80kg - a rather heavy head?
I have a small collection of these struts as they come up for ?1 or so for 2 at a local auction, sometimes even less - those over 400N I can't push in by hand - would be good if there was some way of reducing the pressure as the length would fit my X1 mill
Neil Lickfold23/04/2019 03:17:15
556 forum posts
102 photos

Some struts are adjustable in their pressure, and have a pressure bleed off screw at the fixed end of the cylinder. It is about a M3 or M4 set screw.

I changed mine around and now have it correctly mounted. Also made 3/8 hex adapter to use with my battery drill or the 3/8 ring spanner. No need for the really long handle that can sometimes get in the way when the table is close to the column.

3-8-adapter.jpg

SillyOldDuffer23/04/2019 09:53:18
4536 forum posts
971 photos

Further to Simon's query about Nm, I did a bit of internet searching last night whilst watching telly and found a mix of struts being sold in Newtons (which I understand) and Nm (which I don't). If Nm is a typo, lots of people are doing it! No explanation for Nm as applied to struts, nor a clue by finding an example measured in both N and Nm.

Nm sort of makes sense as a measure of torque force, but as Simon said, the theory doesn't wash. In the non-torque sense a Newton Metre is a measure of work - a Joule - but that makes no sense at all. It's a mystery...

Dave

Neil Lickfold23/04/2019 11:10:16
556 forum posts
102 photos

Dave, here is a link to info about gas struts, **LINK**

Anyway, it does appear that there is no Logic to Nm on the labelling. The strut is pressurised and that is measured in N force , or KG force or Lbs force.

Nm is a torque measurement, like ft lbs is a torque measurement as well.

Hope this helps people in the future.

Nick Hulme27/04/2019 22:12:43
694 forum posts
37 photos

I use a length of thin walled plastic tube over the strut on my benchtop CNC mill, it's just a bit longer than the rod and is a sliding fit over the housing so it drops into position to keep the strut clean but can easily be lifted to check everything is still spotless underneath.

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