Hey guys. If you saw my other recent post asking about a gearbox you would have found out I plan on making another rover. Eddie helped in making some suggestions in how to put the gear box together and a site where I found some great parts for it too. The idea is to use a lynxmotion U-channel with miter gears to transfer the power 90 degrees to the output as the motors will be parallel with the side of the bot. I have completed step one of my plan and I bought a drill press. Nothing fancy, a small 10 inch 5 speed press from Ryobi. The next step is to buy my stuff from lynxmotion. I was planning on using 4 PGHM-05s: lynxmotion.com/Product.aspx?productID=581&CategoryID=71:
Can anyone throw in some input to whether these motors will work with tracks on a 2-3 lb bot? I calculated that each motor will produce ~.689 ft-lbs (122.609 oz-in) at the outside diameter of the sprocket, I feel this is enough but not sure.
I am also ordering the U channel for the gears to sit inside of and provide a strong platform for the gear box. lynxmotion.com/Product.aspx?productID=520&CategoryID=96
I will upload a sketch of it later if people are still confused how the gearbox will look.
Well I got around to finishing the drawing of the gear box. Using the specs of the gears and the trace of a U channel I made an exact size gearbox. It’s a tight fit but it seems like everything will fit nicely. Here is the drawing:
The nice thing about this gearbox is that the motor mounting holes fit up perfectly with the SES holes on the aluminum U channel so I can simply bolt the motor onto the U channel and then bolt the U channel onto the side of the bot. I’ll be making the order sometime this week from lynxmotion. And I’ll order the gears and bearings later once I’m sure the motors will bolt up as I hope.
Jim is you could confirm that the PGHM-05 has the same mounting holes as the SES, it would be very helpful :]
Have you considered how to maintain the loading of the miter gears? One way is to use bellville (sp?) washers between the bearing and the gears. Normally you need to be able to adjust something. I’ve made differential drives for arms this way with miter gears. the gear engagement was controlled by the dimensions of a milled and bored block, the three miter gears run against three faces. Two pulleys on two of the miter gears flank the block, and the third pulley and miter gear runs in between to make up the output shaft. bellville washers load the miter gears.
You might consider making up a fixture for your drilling, which must be very accurate. And I didn’t look up the bearing OD, but I’ll bet it’ll require a rather large drill bit.
New drill press? How much time (experience) do you have on the drill press? Large bits tend to ketch on thin sheet metal. The bit grabs, and attempts to spin the stock. Dangerous! Be sure to properly clamp down the stock while machining. We want to keep you save and on this list!
For precision holes a boring tool is often used. Reamers are another solution, but here again, the bearings will probably require a large hole.
They line up somewhat, not perfectly though… You will definitely need to drill the center hole, and you will probably need to enlarge the four satellite holes.
Hmm, I will defintely look into the belleville washers, It’s to keep the gears together tightly? That’s what I gathered from my reading up on them. Assuming it would load the gear on the horizontal shaft by pushing it inwards toward the output gear of the motor?
The good thing about this gearbox is that “the gear engagement is controlled by the dimensions” of the aluminum U channel lynxmotion carries.
And I managed to find bearings that have a perfect 8 mm OD (the diameter of the large hole in the SES mounting holes) with a bore of 4 mm (the size of the output shaft) So basically all I have to do is slide the bearings into place and put the shafting on the gears and bolt the motor up. Really convinient. 8)
As to the drill press, I have plenty of time with power tools to know the dangers of them. I used a drill press in a shop class before but I never had the issue you described with a drill press, that has only happened to me with a normal cordless drill. I also bought a hefty vice for the press so I should be all set, thank you for the concern though
The reason I bought the drill press was to be able to create set screw holes in the gear hub and I was tired of drilling slightly angled holes in all my chassis and work, it’s a relief to have the right tools to get the job done right.
That’ll be amazing if you can just fit it together! That seldom happens except for a “system” like SES.
I am very impressed with SES. I’d be curious to hear the history of the SES products. Who thought 'em up? I thought Jim said he had an EE background; I could be mistaken.
I’m glad to hear you’ve had some experience! Bigger drill motors, more torque, more things to watch! As for drilling and tapping the set screw holes, I assume you know what a V-block is.
Good luck on your project! And be sure to post pix of your progress. And if you’re not already on a model machinist’s list like Sherline (on Yahoo), you might consider joining. You’ll undoubtedly find it valuable if you start doing more mechanical construction.
Please forgive the short distraction… I do have an EE degree from ITT Technical Institute. I graduated in 82, so it was thick with transistor theory, RF communications, book heavy math formulas, etc. Computers were as big as a fridge and made by a company called DEC. It would be 12 years later before I built my first robot. In the October 1994 issue of Circuit Cellar I read an article from Scott Edwards where he made a simple pic based servo controller. I was selling the Lynx5 robot arm within a year using his servo controller. These arm parts were machined from Foam PVC. As time and resources allowed I designed all kinds of custom parts. Some were injection molded, some were machined, some where stamped, etc. I made all parts I designed available separately for those who wanted to DIY their own robotics. The list of parts grew and grew to the point we just started calling it the Servo Erector Set. Wow it’s really been 15 years since I read Scott’s article…
And along the way you have obviously developed many ME skills as well! Again, congratulations on your success.
Please tolerate another diversion; I’m curious about the SES 2DOF legs development. I found two leg builds, but only one is currently offered. Possibly because everyone wants 3DOF legs?
I ask because both builds look interesting, and I’m considering a build with minimal material costs. I’m sure 2DOF legs have limited moves compared to 3DOF, and probably preclude the motion translation needed for omni-directional moves. What other limitations might hinder or preclude their use? (new thread optional)
The best 2DOF leg is one that implements a mechanical advantage when in the down position. I have implemented many styles of this with SES parts, but they often exceed the price of another servo. I have been wanting to make the following into a kit.
But it’s expensive to build compared to a 3DOF hexapod. The SES needs more 2DOF leg options. I will eventually make it happen. So anyway, 2DOF if done right can hold more weight with less power, but it can only be controlled like a tank, no crab walking.
That confirms my suspicions. Still of interest, and for the purposes of the project I have in mind, “tank” drive will suffice.
Very interesting mechanical linkage! And I can see why it would be light weight.
I’m still interested in the 2DOF leg, I see that the 2DOF leg kit that you sell is not the one with the pantograph (?) linkage. Build80 DOES have a parts list, which is great, are all the parts available?
You might also consider a 4DOF leg! I know, it’s in the other direction of thinking, but could be very useful for more bio-inspired quads (think cat)!
I know of a build 79b, and just visited again to find a few more legs, 81, 84. I’d like to temporarily convert an 82a 2DOF leg build to a 79, which should be simple.
I didn’t see much left-right axis difference in the 82a legs I’ve built, is it necessary? How much offset is there? Good mental (metal?) exercise to reverse a leg from right to left!
OK, 80 is 080. I can see some difference.
I think some builds might have been in PDF (convenient). Do you choose to just host HTMs at this time?
Two hours at work and I get ripped out my thread and rolled in the mud…
I have got a couple questions.
How does a V-block help in getting the set screw holes? Looks like it is for pure cylyndrical objects like piping, unless I would rest the hub of the gear in the top of the block instead of putting the whole thing in there…
What is the difference between a normal drill bit and a boring bit? Where can I pick up some boring bits?
Alan I will definitely keep you guys posted on progress. However I may need to go pick up a digital camera…
<<<<<<<<<<<>>>>>>>>>>>>>
How do you guys recommend I keep the shafting and gears in place? I was thinking either normal collars with set screws or E-clips on the ends. The internal gears I could always keep in line with spacers and washers…
You set up your stock on the v-block(s), clamp it, accurately align to perpendicular and on a diagonal, then drill and tap. This process insures that the hole is in the right place, and the stock (gear) doesn’t move on you while you drill/tap.
It’s a boring tool, which is a ground tool bit similar to a lathe bit, except that it’s held in a rotating boring head. It “flies around in a circle” inside the desired bore, to make a very true hole.
Drill and tap the gears, be sure to put flats on the shafts. Otherwise, the setscrew (grubscrew) will leave marks, and if the gear spins, you’ll be hard pressed to remove it later.
You have external gears as well? Flats and setscrews are still acceptable, you’ll need some tooling to cut the slots for the E-clips.
Oh ok, Thanks for that clearing up Alan. Boring tool. I’ll look that up later
As to putting flats on the shaft,I assume I can buy a bit/tool compatible with the press that will put a flat on the shaft. I have seen some flat bits in the machine shop I work at used with CNC mills. Will those work? Sorry for all the questions, really a learning experience for me.
Normally endmills are used to make flats on shafts. You hold the shaft in your v-block(s), and make a few passes on the stock until you have maybe an .080" deep flat (depends on shaft size).
I have seen this done in a drill/mill, or drill press with a “compound vise” (?), a vise with X and/or Y feed screws. You’ll need an end-cutting endmill. Try MSC. Now you’re talking about machining forces, so you MUST have the stock securely clamped down; and FEED the stock with a leadscrew to gain the necessary cutting forces.
Of course, a bench grinder or Dremel tool has been put to the task occasionally!
I think you’re describing an endmill. yeah, they work!
I also bought a hefty vice for the press so I should be all set, thank you for the concern though 
