Cable drive

I just wanted to quickly let you know a little more about the cable drive. I know some people are unsure of its abilities so let me put those worries to rest.

The reason I went this route was to create a system that does not require special belts that are unavailable in the retail world for the most part. I also wanted to eliminate the problems found with belt driven systems like backlash from the rubber compressing or bumps from the teeth going over the idler pulley. This lead me to a cable drive system like found on a plotter or scanner. Growing up in the marine world I was familiar with roll-on roll-off winches and hoists so I knew the system could apply a lot of force and would not slip.

A lot of people have asked how it works and I have tried to explain in the instructions on Tantillus.org but it will only be clear once I make the videos during the assembly of the machines from the Indiegogo campaign. I will try and explain it here as well.

The two rods with the drive gears on them have holes drilled at each end to allow the cable to pass through them. The cable is then wrapped 5 times on either side of the hole in opposite directions to allow it to roll-on and roll-off but only up until the fixed point where the hole is drilled. This fixed point is what makes the system solid and prevents any slippage. We are only actually un-wrapping the cable 2 wraps in either direction and the other three on each side are to further give traction to the cable and creates an offset in the two lines that allow the cable to pass by the X/Y end. We then need to wrap the cable around the rod on the opposite side (idler side) 7-10 times to get the offset on that side as well so it lines up correctly. Then one of the cables goes through the X/Y end and through a loop in the other end of the cable and back through the X/Y end. This allows you to simply pull the end of the cable and it cinches tight. You only have to tighten the one bolt in the X/Y end to secure it. This makes it easy to align the bars as you just undo the one bolt and move the X/Y end which has the cable running through it and then re-tighten the bolt when square.

The cable I have chosen to supply with the kits on Idiegogo is a braided high test fishing line from "Power Pro" and is made of 100% spectra fibre. I did some testing with wire rope and it should work but I have not done enough testing to make any solid conclusions as it may fatigue over time. But for those of you wishing to try it is usually called stainless leader line and is sold in some fishing stores.

The spectra fibre is incredibly strong, but why should you believe me. This is what the manufacture Honeywell says about the fibre.

"Pound-for-pound, it is 15 times stronger than steel, more durable than polyester and has a specific strength that is 40 percent greater than aramid fiber. Polyethylene is a remarkably durable plastic, and scientists at Honeywell have captured the tremendous natural strength in the molecular backbone of this everyday plastic to create one of the world's strongest and lightest fibers.

It also exhibits high resistance to chemicals, water, and ultraviolet light. It has excellent vibration damping, flex fatigue and internal fiber-friction characteristics, and Spectra fiber's low dielectric constant makes it virtually transparent to radar.

Spectra fiber is used in numerous high-performance applications, including police and military ballistic-resistant vests, helmets and armored vehicles, as well as sailcloth, fishing lines, marine cordage, lifting slings, and cut-resistant gloves and apparel. Honeywell also converts Spectra fiber into the Spectra Shield family of specialty composites for armor and other applications."

These properties have lead to Tantillus having no detectable backlash and very accurate steps per mm. Giving Tantillus amazing layer alignment as seen here.

Note:These photos were taken with a microscope and are of 0.2mm layers and 0.25mm.

 
All of this results in a system that has surpassed my own expectations and hopefully yours.