I am working on a new compact machine that uses a timing belt and Vee rail instead of a drive wheel. It also uses a double stack nema 24 motor (a nema 23 could be used instead but has a smaller shaft) So far the machine looks like a very reasonable design. It costs less than the current design and seems to have more than enough power using just a 5 amp 24 volt inline power supply. No need to build your own power supply. The timing belt will not allow any slipping. The inexpensive vee rail is aluminum and the vee pulleys are nylon so this model might not be as durable as the drive wheel design but the parts are inexpensive and easy to replace should they wear out. The prototype is very skeletal and will eventually be put in an enclosure. The new machine (without enclosure) weighs less than half what the drive wheel torroidal transformer model weighs.
I discovered a few things about eliminating noise and that nasty Geiger counter noise that it causes. I never had much of a problem before but the new design has more metal and some longer signal and power leads which increases the chance for picking up noise. I added ferrites to the limit switches as before but also to the signal lines to the gecko from the Shagmatic board. I also connected the metal vee rail chassis to the power supply ground. The new machine uses a 24 volt power supply so it can power the shagmatic board using a little voltage regulator board. I also added a .1 mf capacitor at the power supply connector on the Shagmatic board because of the long leads from the voltage regulator to the board. Another option would have been to place the regulator closer to the Shagmatic board but I am not sure how much difference this would make.
At some point after testing this stepper motor version I plan to substitute a servo motor. This will make an unstoppable machine that will not lose steps and will have much more power. It will require at least a 48 volt power supply so the little voltage regulator board will not work and I will need to figure out another way to provide 5 volts to the Shagmatic without requiring an expensive 48 volt to 5 volt converter. I have plenty of these for my own use but want to figure out a way for others to avoid this expense as the converters are not that easy to find as surplus.
Sounds great – cheaper always sounds great :).
It is cheaper to build but I don’t think it will be inferior in terms of capabilities. Other than the new Nema 24 motor and the Vee rail system, I built it with stuff I had on hand. The motor pulley is a little small so I am going to experiment with some firmware mods to bring the speed up. Might need to change the pulley to get the right torque/speed capabilities.
Makes sense. I just want a part list and online vendor links, lol. My current machine – wiper motor based – is so bulky. I really need something smaller with more capability. Thanks for another great post.
i plan to make a parts list pretty soon. i do want to do some testing first. the step motor is the large nema 24 from Steppersonline. i am still using a gecko driver because they are small and a lot better than the Chinese ones. The power supply is a 24 volt inline block type supply from MPJA. The vee rail stuff including the trolley plate are from http://www.inventables.com i want to do some testing before specifying details like timing pulley size. other than boring the 8 mm hole in the timing pulley, nothing requires a lathe or other fancy tools. if you can not get someone to bore a timing belt pulely to 8mm, you can use a nema 23 step motor with a 1/4″ shaft but i think it is worth getting the pulley bored as the larger shaft is really helpful. another possibility is to use a 32 tooth pulley (this is one of the thing i need to test) with a 5/16″ bore. this is just .0024″ larger than the 8 mm shaft so should not be a problem.
hello,
Do you think it can be possible to use other type of linear guide, in order to tie the shaft to the timing belt directly. Something like this:
http://image.made-in-china.com/2f0j00qyUaBZjGLMcs/Linear-Guide-Rail-for-TBR-and-SBR-Types.jpg
I mean to fix the ball bushing and move the shaft like a aquator instead of moving the ball bushing.
anything is possible. you just need to move the toy back and forth. doesn’t really matter what hardware you use. it is important to minimize the mass of components that are moving as much as possible if you want rapid acceleration.
ground rods and linear bearings should be a lot better than vee rails in terms or strength and durability. the only problem is that you want to pr3event rotation of the driving components so you might need to use two rods instead of one or provide some other key to prevent rotation.
Can you provide more detail on what you would use to prevent rotation?
First I didn’t understood how a rotation can occur, but then I think a little more and you are right.
Did you think that if I try to fix the rod straight to the belt, the belt will not stand the pressure on Y and Z axis and maybe will start to rotate? If I buy a larger belt maybe this can be avoid? I am not an engineer so forgive again if I am off the subject somehow.
i have never made a fucking machine with round rods. i have used smooth stainless steel square tube riding in reinforced fluoroelastomer (flurogold of which i have a ton in case anyone wants to do it this way) bushings. this worked quite well to make very compact machines. the “one tough fuck” machine in the banner of this blog is an example.
if you want to prevent rotation with round rods, the most common method is to use two rods. for a fucking machine you can get buy with fairly small diameter rods unless the length is extreme. a little deflection is not a problem with a fucking machine as it would be for a milling machine or router. my cnc router has 19 mm rods and is about 30 inches long. it has a little deflection at the mid point. i would guess that a fucking machine could use 12mm rods without a problem. you could even use a smaller rod just to prevent rotation and a larger one to support the carriage. the smaller rod could be in a bushing instead of a linear bearing. the main rod also could be in bushings. they are a lot quieter than linear bearings which make a lot of noise.
the belt will probably not be enough to prevent rotation unless something is done to minimize rotation. if the toy is mounted with a quick release that allows rotation this will help prevent rotation of the carriage. also if the shaft to the toy were mounted under the carriage gravity would help to prevent rotation. if the length of the rod is short enough, belt tension alone could be adequate to prevent rotation.
if you are going to experiment with a round rod system and want to try a single rod with nothing other than the belt preventing rotation i would design it so that an additional anti rotation device could be added if needed. really long machines will need something and that something needs to be sized to match the length.