Hi,
I’m not sure if something like this has been posted before, but I thought I would share a spacing calculator that I made. It calculates the correct spacing using vex spacers and washers to three decimals places of accuracy, or the closest possible one, with the minimum possible number of spacers. It isn’t useful for most things, but some situations call for stange spacings and this can fill the gap accurately. Unfortunately due to some rounding issues some possible spacing configurations get changed, but most are unaffected. After worlds I’ll try to fix that and add some features.
http://www.dvhsrobotics.com/Resources/designtools
Adding in options (checkboxes I assume) for using only one kind of spacer (ie, white ones or black ones, only washers, no washers etc) could be useful
The vex community is so cool.
person 1: “What spacers do we need.”
person 2: “I can write a java script thing to find it for you.”
person 1: “Or you could do it manually.”
person 2: “but that is not any fun now is it.”
This is amazing.
If you made this an app, I would buy it. Just putting that out there.
I second what 400x said. I would certainly buy it as well. Great job and thanks for sharing.
I like it. It’s a very clever idea. 
ditto. make it an app 
if this came out at the beginning of this year, it would have saved my robot from being imbalanced, seriously, i wasn’t able to balance my robot without programming until February before provincials.
Thanks for the feedback!
Just curious, is there any specific reason why you’d like me to make an app? I could, but the site formats relatively well on mobile, and its much more time consuming to make a nice app. After I find some time I will definitely add some features like selecting what spacers you have, how many you have, pictures, etc.
I would suggest first fixing the spacer sizes. Namely the black spacers. Although they are given in millimeter measurements by VEX, looking at the CAD gives a greater accuracy as to their sizes. The “4.6mm” spacer would be ~0.181" doing simple conversion, however the CAD file of the part reveals that it is 0.187". Similarly, the “8mm” spacer would be ~0.315", but is actually 0.328". Also, at some point VEX changed their steel washers, and so their thickness changed too. The new ones appear to be much thinner, but I haven’t done any measurements so I cannot help you out there.
Either way, this is a great idea, and if the previously mentioned size changes for black spacers are made, I’d use this tool rather than having to do the math myself. Thanks for making this!
Huh, thanks for the information. We haven’t done large scale checks, but we did check a few 4.6mm spacers to be approximately accurate on a pair or capilars. I shall double check with larger samples to verify. It may be possible the CAD is inaccurate? I’ll check washers and 8mm spacers as well. At some point I doubt these parts are manufactured with such low tolerances, but 0.01" is rather large.
Nice job.
What is the priority of pieces? We tend to like white nylon spacers above black ones as they hold closer to 1/8" increments Vex likes so much.
- Black spacers over bigger OD white ones
- teflon spacers vs steel washers? (reduce friction)
Wish list:
- incorporate a choice of wheel, gear, shaft collar, and bearing block? - that could complicate things as you need almost a 1/8" space from the bearing block to clear the heads of the screws on the bearing block.
Thanks for the feedback! As for the priority, there really isn’t one, the alogirthm just tries to minimize the total number of spacers needed to make the spacing requested. The reason why you may see some strangely inserted washers and black spacers is that they have spacings which aren’t a multiple of 1/8 " which allow for fun combination optimization allowing it to find spacings you wouldn’t think are possible without lots of washers.
Today I got a team member to measure some of the black spacers and got that the 4.6mm spacers to be 0.18" flat and the 8mm to be 0.319". Error can be attributed to manufacturing and measurement deviation. As such, I will leave the numbers for the spacers as is. As for washers, I’ll try to get some tests on them later.
I think it would be really cool if you could essentially put the width of the tower or drive base, either in inches, or in holes apart, and I think adding wheels and gears, along with spacers and washers would be great.
On my robot, I tend to use these things called collars. They posted provide some different options for spacing that I have found useful.
On my robot, i tend to use these things called spacers. They are a lot lighter and you can space any size, even smaller spaces that collars cant space. You should try them sometime.
I think he means that collars should be added to the calculator, because you often need one or two of them on an axle in addition to spacers.
I think it would also be cool to be able to select what needs to be put on the axle, such as a wheel and 2 collars, and then calculate the spacers needed based on the total length.
I agree.
My team also does not have any of the white nylon washers, so we have to improvise, or is it engineer?
The regular shaft collars are .25" wide. I also agree that it would be useful to have the ability to select certain parts you will have taking up some space as well, though you could just subtract their size from the value you enter. Overall though, this is a very helpful calculator that would have made my life a lot easier a few months ago.