rolamite machine

[Art]

Got the Joe's CNC 4 by 4 Hybrid running and it is a nice hobby machine but needs more beef. Great learning experience but not a MM. I am going to start on a MM 4 by 4 but instead of lead screw or R&P I am going to try rolamite. Not any machines of any type on the web that I can find that use the rolamite. Should be interesting. Since I have the router I winn make the Y plateform from 1/2" al plate. Apparently the DXF files are no longer on site so I guess that I will have to draw them from scratch which is a PITA!

[MetalHead]

Art I sent you a PM - I have sets available for sale in my store.

[Art]

I just wanted the DXF files because I need to make changes to original design. In rolamite version only 1 motor used on long axis though gantry is still driven/pulled from both sides. Also will use lead screw on Z.

[KenC]

This will be interesting! will keep my keen eye on this project!

[liaoh75]

I'll Second that on Ken's statement! Looking forward to pictures!!!

[Art]

Here is an article on the rolamite published in 1968 by Popular Science. http://www.rexresearch.com/wilkes/1wilkes.htm#pm Other than a component of nuculear weapons trigger, air bag deceleration detection and a commercial postal scale i haven't found any uses. Reliability is EXTREMLY !! important is 2 of the uses. The big question is will it scale up!
First step is to build a 4by4 frame and and load the gantry with about 60 lbs of weigh and do a series of hundreds of rapids to see if slippage will be a problem. What wories me is that such a clean design is not in commom usage.
Weird that that bussiness has been in the crapper for the last 5 months while I have been going through cancer surgery/radation/cemo. Orders have matched my ability to spend time in shop so it hasn't been a bad thing. Build will take back seat to bussiness and learning Aspire so will probably be several months before tests can start.
First big step is to decide in band material. Metal would be nice but I don't know any thing about the stress/flex infolved. Anyone that has any experience in this area please share your knowledge. I would prefer 1/2" wide belt but 1" is not a problem.

[KenC]

No experience what so ever....BUT I'll participate base on what I read from the article.
I recon it requires a belt that doesn't stretch that much... Metal band would be a better bet.

[TheDave]

I don't know if this will work, but...
http://www.fennerdrives.com/high_performance_composite_vbelts/powertwist_home.aspx?gclid=CO6gk667oaQCFQHW5wodxyk b4g

I've replaced every single v-belt in my shop with this and I love it!

[Art]

I had one suggestion of .003" metal band from McMaster Carr. It has the strength but number of flex cycles before failure is unknown. As I see it there are 2 options. Using a flat belt of composite material that has almost no strech and probably 1" wide. Second is a metal band that will have to last several million cycles of flex. The load on the band will be 60 pounds at speeds up to 300 IPM. The strech factor is critical as the band on a 4' machine will be about 8' in length. My Shade Tree University degree in Southern Engineering says that metal would be the best way to go. If anyone knows of a vendor that migh have what I need please send me their contact info.
I am going to cut all metal parts from plate AL and bolt the assemblies togeather because with care the JoeCNC will mill the AL and I don't have capability to mill steel.

[KenC]

I would recon the strip need some spring quality too. and SS stretch a lot more then most ferros material.
I can think of band made out of shim sheet/strips. or those holding strips (still don't know what they are call correctly) use on good-old magnetized drafting table to hold the paper down.

[Art]

How about wire rope? 1/8" has 1200 lb breaking strength and also it is used in plotters with 2 or 3 wraps around the powered shaft. Initialy Iwouls think that it would take 1000 or so high speed rapids to eleminate any internal slack and tighten the rope.

[TheDave]

The article you linked to mentions what they use...

"But, I wondered, doesn't all that flexing of the band cause it to wear out eventually? Doesn't metal fatigue cause it to break? Those were questions that bothered Sandia engineers too, at the beginning. Now they've quit worrying. The beryllium copper bands used in Rolamite have proved to be so sturdy that they show no sign of metal fatigue after 1,000,000 flexures. At that rate, the engineers figure, the band in a Rolamited home light switch operated 10 times a day would last 300 years. A Rolamited bathroom scale used five times a day would not wear out in 600 years."