What are "Gas springs" for grinders?

chknifemaker

chknifemaker

Joined
Jun 30, 2013
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207
I have been hearing about the "gas springs"(they mite be air-not sure) like on the Uber grinder. I was wondering two thing:
-is this better than conventional stuff in practice?(I'm not talking about cost just performance, though cost comes into every decision)
-how do they work?
(I did look around on this forum and on Google but didn't find what I want)
Thanks
 
Yes, some folks are using the gas springs instead of a conventional spring to apply tension to the belt. I've been meaning to adapt my KMG to this but haven't gotten around to ordering the parts. McMaster-Carr carries everything you would need and the cost is about $15 for the parts. Basically all you need is the gas spring, 2 brackets, and 2 eyelets that match the threading of the spring. It works similar to a gas shock on vehicles. The spring can be bought in different lbs. of force applied. For my KMG, I'm going to order the 40 lbs and go from there. I've read that tracking can be greatly improved with this mod.

http://www.mcmaster.com/#gas-springs/=s74li6

Here is a thread on the topic

http://www.bladeforums.com/forums/showthread.php/949335-How-to-make-a-KMG-better-(GIB-content-also)
 
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Do you have a Beaumont KMG or a clone?

I have a NIB Beaumont 2hp variable speed, just curious if it will work with simple modifications

It's not out of the box yet . .

Steve
 
sdemars said:
Do you have a Beaumont KMG or a clone?
Click to expand...

Who me? Yes, I have a KMG from Beaumont. If you look at David's KMG in the link I posted, you'll see he has the older version. The attachment of the tracking wheel arm to the main socket body is different than the newer version. I have the newest version and you should as well. The newer version uses three pieces instead of one. Two "triangles" and a hard mount. Basically my goal is to get the correct length gas spring that will allow me to add new "triangles" to increase the distance/height away from the socket body. Then I can just drill and tap into the existing tracking wheel arm without having to add the extra arm extension like David did on his grinder. It will raise the height of the tracking wheel some of course, and in doing so I will have to make sure none of the attachments are brought in too far as to bump into the socket body, but I'm thinking it will work. The mod itself should be easy enough.
 
p9aKF6w.jpg
The gas piston and two brackets are from McMasters Carr parts # 9416k29 , 9416k11 , 9416k84. The new lever is 1/2 x 2 inch aluminum bar which has been milled down by half where it contacts the original arm. A roll, pin keeps the lever from rotating. I first saw this modification on David Sharps website and made my similar set up with the same piston parts. I used a 30 ib. piston the same as David and it works fine. Larry
 
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I don't know if the gas piston will last longer but I was on my second stock KMG spring when I heard about the gas piston mod. The stock coil spring did not seem to compress to the same poundage each time I pushed down on the arm and locked it. The new spring is 30 pounds which IMHO is the right amount of pressure to put on the belts but you can certainly try the 40 pound model. The new set up is smoother and always the same tension. Does it improve the tracking???? I am not certain because I tightened the tracking mount after installing the piston and the belt tracks like perfect...It could just be all in my mind but the piston is much easier to use and may out last the coil spring. Others have agreed that it is superior to the stock spring and I would do it again if I buy another grinder. We are only talking about 15 bucks and some drilling and tapping. ( I only have 3 taps because I buy them one at a time when needed) The pistons can be replaced cheaply and quickly once you set it up. Just my opinion...let's hear from some others. One other mod that is easy is to switch the stock 1 inch tracking knob to a 1 1/2 inch zinc plated knurled knob which is much easier to adjust. This is a real improvement to me. Larry
 
As I understand it, at any given position/tension, a gas spring doesn't do a significantly better job as a spring than a correctly-adjusted conventional coil spring. It will not inherently provide better tracking, nor will it cook your meals or improve your sex life.

The advantages it has are twofold.

First is that, unlike a coil spring, the gas spring rate changes very little over the stroke length, resulting in very little change in belt tension when the belt length changes (for instance when you replace an old belt with a new one). There is therefore much less need for frequent adjustment (Larry's point).

Second is that the gas spring provides both the springing and a significant amount of damping in a single package, and damping is something that is difficult for the average guy with a home shop to achieve by other means. I suspect this is the improved smoothness some have reported.

The result is more constant tension and less transmitted vibration.

Not having to deal with varying tension and vibration will give the tracking system an easier time and allow it to work as intended.

I'm fairly sure gas springs will not make a bad grinder good, but they can make a good grinder slightly nicer to live with.
 
You can use clamps to play around with the best positioning of the gas spring before you permanently install.
 
Gas shocks look cool I'll give you that, but the Manufacturers only guarantee 250 000 thousand cycles, I have had 3 cars that the gas springs failed on the trunk lid, and they don't fail all at once like a spring breaking they fail over a few months losing pressure, figure out how many times a day you change your belts divided by 250 000 and that will give you the minimum lifespan of the spring

Even though these springs have relatively short lifespans I plan to use one on my next grinder just for the cool factor ;0)
 
Interesting accessory .................... my wife hates anything I own that has available "accessories" ;) However, in this case, I like the adjustable belt tension that the conventional spring provides. I don't necessarily use the same belt tension for my contact wheels as I do for slack belt or roller platen use. For instance, when my roller platen belt is set loose I'll adjust my belt tension to conform to that loose roller belt setting. Same goes for slack belt grinding. YMMV


:thumbup:
 
Air cylinders are also an option. They have a shraeder valve so that the air pressure can be change if needed. Don't know what sizes they come it.

What amount of travel is really needed! If properly positioned, I would guess as little as 2-3" of travel would be ok.
 
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