mini mill gas strut

[Brass_Machine]

Swede,
Maybe I wasn't clear. That is not my website. I copied the cable lift from RysiuM. I'm sure he would be flattered by your compliments.
Alan

Hey Alan...

Do you have pictures of your version? I am curious to know how it works as well? Did you use the same gas springs?

Eric

 

[miner49r]

Eric,
Pictures are forthcoming. I have the mill torn down for mantenance. Should be back together tonight. Tram .
tomorrow.
Alan

As Promissed. My clone of the Rysium Compound Cable Lift.

 

[miner49r]

Two more.

 

[Brass_Machine]

Thanks!

I like that design. I think I am going to try to imitate it? I saw that rysium used gas springs with six inches of travel. Is that what you used? Do you find it limiting? Also, did you make your pulleys?

Eric

 

[tomrux]

two ropes holding the weight means 6 inches of ram travel will be doubled to 12 inches of head travel.

Tom R

 

[Brass_Machine]

two ropes holding the weight means 6 inches of ram travel will be doubled to 12 inches of head travel.

Tom R

Derp! You are correct. Wasn't thinking about that.

 

[techonehundred]

Your installation is looking really good. To me this brings up a question, So if you have two struts @ 55 #'s, even with the weight cut in half by the travel, will that be too much for the head since it only weighs 30#s? I am asking because I found a 50# strut with a 14" strokeat a local surplus store and was wondering if it was too much.
I also mounted my rack so that it sticks up about 3" above the column. It really does make a difference when trying to install 1/2" drill bits above the vice and work.

 

[miner49r]

Eric,
With the Z-rack extended above the column the head has a full 12" of travel. The gas springs I used have a seven inch travel allowing me to be preload them. You can see the 3/8" eye bolt and threaded coupler I used for loading the springs.
My original thoughts were to use to dual rate springs when RysiuM showed me his setup. The gas springs made it a "no brainer". As RysiuM mentioned in his notes, there is a slight delay in the gas springs where the cable goes slack. (it is slight, yet noticeable) Maybe a combination of springs and gas springs would overcome this.
Alan

 

[miner49r]

Tech100,
There is quite a bit of lifting force. The #55 struts were salvaged from an old truck tool box and were my favorite price. Is a positive lift better than a floating balanced head? I don't have the answer to that. At this point "head drop" is no longer a worry. Your milage may vary.
Alan

 

[petertha]

I was wondering the same thing. I suspect part of the issue is how they rate them. Is it's analagous to a spring, one would think it must be a function of their compressed % or position? Maybe maximum?

I would thing you would want the head it 'almost balanced' so it still wants to come down on its own but still makes for easy up-cranking assist within the typical range of the head, no? Floating up like a balloon after releasing the locks would be weird.

Here is some sizing/terminology info I found, maybe helpful.

http://www.mcmaster.com/#about-gas-struts/=guo2ju

 

[Ken I]

The rate of pressure rise is proportional to the square of the diameter ratios (for a quick and dirty calculation).

For a 10mm rod, 22mm bore gas strut this wil be (10/22)^2 = 0.206

or a 20% increace in force over its stroke (guestimate).

More correctly for a proper V1 / V2 calculation if you start with a volume of 1.00 then less the 0.206 rod volume entering = 0.794

1 / 0.794 = 1.259 or 26% increace in pressure

ie :- 1 / ( 1 - {[d/D]^2})

Normally there is a small quantity of oil for wetting and lubrication which will not significantly affect this - but some applications contain a lot of oil either as an end of stroke damper or to deliberately ramp up this rate.
Some are made with a large redundant volume (the rod is a lot shorter than the tube) to reduce the rate.

Ken

 

[Blue_Rock]

Very nice mod Alan.

 

[miner49r]

Thanks Simon,
The credit really goes to RysiuM at the GrizHFMininill group. If I had to change anything I would put #40 struts instead of the #55 ones. I would have to buy them.
Alan

 

[Max762]

I just received my air spring kit from LMS and am about to install. I read somewhere while researching this mod that the LMS instructions where incorrect as far as where to drill the hole for the lower end of the strut. But, now I can not find that post again.
Can anybody shed any light on this before I go ahead and drill the hole?

 

[rleete]

That was my post over on Machinistblog.com. http://www.machinistblog.com/forum/mini-lathes-mini-mills/lms-gas-spring-conversion/#p311

 

[Max762]

That's the one I was looking for, thank you.
Good news is that they must have updated the instructions. The ones I received say to place the hole 15" down from the top, which is much closer to your number than the 12" figure they gave You.

Thanks again for your reply.

 

[rleete]

I had emailed them back when I made that post. Nice to see they are paying attention. That kind of customer service is what keeps me buying from them.

 

[ZipSnipe]

I know this post is old but I would like to ask Alan if he finds the stronger springs better for drilling operations?

 

[zoltan]

I installed my gas spring not too long ago, but instead of drilling another hole in my column, I made a mount for the bottom which allows it to rest on the base. It seems to work fine:
http://benchtopmachineshop.blogspot.com/2013/06/mill-gas-spring-installation.html