There are basically two types of cylinder, hydraulic or electric. With hydraulic, you would require a motor driven hydraulic pump and distribution valve set to provide and control oil flow. It is more complicated, expensive and suitable for metal models. You would not able to make them for yourself without a CNC machining lathe but can be purchased from suppliers such as Manolo Gomez.
On the other hand, the electric type is easier to handle and you can make them for yourself using hand tools. One example is to use the hand drill bit driven by a motor with the nut fixed inside the tube. When the shaft is turning, the tube will slide in and out of the cylinder simulating the linear action. You can also purchase them from supplier such as CTI-Modellbau.
After considering different options, I decided to go for electric type and make by myself using the original plastic cylinders as the body. From the information of various conversion projects or part suppliers, I understand that the linear speed and stroke of the cylinders as below:
Liner speed: 10mm/s
Stroke: 40mm for bucket, 80mm for stick and 70mm for boom
A M4 threaded shaft is used as the driving shaft which is turning in a M4 stand-off to cause the cylinder rod moving in a linear direction. Every turn of the shaft will cause the stand-off to move 0.7mm. Therefore, you would need a motor of 900rpm to achieve a 10mm/s speed.
Step 1:
The geared motor has a 10 x 12mm cross-section area. You would need to round off the edge enabling the motor to be fixed inside the original cylinder body of 10mm diameter.
Step 2
Cut the threaded shaft to appropriate length and connected to the motor via a light hub. The light hub is made of plastic material with copper collar for set-screw. The tube of the light hub is accommodated for M3 but there is no problem to screw the M4 shaft into it, providing enough strength to hold the shaft. The shaft end is fixed with a screw nut as stopper.
Step 3
The M4 stand-off is fixed to the tube of the rod, you would need to grind-off a little bit of the edges. Then put the cylinder body and rod together. Fix the motor with plastic straps into position.
Step 4
Connect the motor with power to see if the rod slides in and out of the cylinder smoothly.
I admit that this is not a good looking option for such modification. However, if you do not want to spend money on expensive electric linear cylinders, it is the easier and economical way to achieve with only hand tools.
Parts used are:
4 x FingerTech geared motor US$63.80
2 x 300mm M4 threaded shaft US$8.00
4 x M4 stand-off US$3.00
4 x screw nut US$1.00
4 x FingerTech light hub US$9.90
Total cost: US$85.70 + shipping
沒有留言:
張貼留言