Hey guys. On much thought and thinking I am going to make a 4 motor rover. 2 in front and 2 in back. With this design I would like to keep the motors parallel to the sides of the rover. This is going to require a 90 degree gearbox. Does anyone know where I can get a gearbox that will handle the stresses of this and accepts a 4 mm input shaft? (Planning on using the PGHM-05) I have looked many places but can’t seem to find any.
On top of that for a custom gearbox many of the miter/bevel gears i have looked at have a larger bore than the output shaft. Can anyone offer a decent place to find miter gears to build this?
Also if I went the cumstom built gearbox I was wondering if anybody would be willing to offer thair services to cut and drill the metal that I would be using to mount the motor on the gearbox and frame. preferably somone who has the proper tools for this. Any services would be paid for after later discussion.
If anyone feels I could make this power transfer in a better way please let me know.
Hope to become re-involved in robotics since I fell out of it. It’s good to be back. 8)
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I found a site with some decent looking gear boxes. What do you guys think? I emailed them asking about prices and if they allow orders in quantitites of <10
looks like the PGHM can output about 6W around 100rpm tops so then looking at the teausa site the low cost gearbox that could work with that is the PV 15. two issues there, you’ll need a shaft coupler betwen the two different size shafts, and the gearbox comes right out and says zero axial load which suggests (to me anyway) you will need to couple to a bearing supported shaft for your output. doesn’t seem like a very straight forward solution honestly.
I think ideally you would mount a bevel gear to your motor shaft and use a bracket of some sort to support your output shaft with the other bevel gear. what about a piece of tube or u-channel aluminum? mount the motor to the bottom of the channel and put a flanged bearing in each side wall for the output shaft. making something like that depends heavily on your ability to machine the aluminum with precision…
Thanks for that site eddie. Really a wide selection I can choose from. Is there any real difference/advantage between miter and bevel gears? Then look almost the same. Also as far as the gears go I found some with the 4 mm bore like i’m looking for here
They are miter gears, but they seem to fit what i’m looking to do better. It seems that these do not have a set screw which isn’t too much of a big deal, just drill a hole and tap it. How ever this does seem to be exactly what I need. Jim has 4mm pillow blocks on the site which I hope he is still selling…lynxmotion.com/Product.aspx?productID=228&CategoryID=6 which would be perfect for this set up.
However, if I Jim is no longer selling those I was wondering if someone would be able to machine them for me or help me get them machined through a company (recommendation, help in designing)
The only drawback to buying these miters gears is that 8 of them for the bot will run me $130 . ah well. I also plan on picking the shafts I need there. Depending on my next pay check I should have the gears within a couple weeks
miter vs bevel I can’t say for sure… I’m ee not me… but ifI were to guess it would be something to do with rotational direction and efficiency.
I’m not sure where you are going with pillow blocks. I seriously doubt you can get the kind of mechanically solid alignment you need between the gears using pillow blocks and a mounting bracket for the motor. most any r/a gearbox you see is cast and machined for alignment or just right out machined from solid “something”. remember there is significant force pushing the gears apart when you are applying torque to the output shaft.
here’s some ascii art of the idea
a a
a a
ba g ab
--wba---g--------abw----
ba ggggg ab
a | a
aaaaaaaaaaaaaa
mmmmmmmmm
mmmmmmmmm
mmmmmmmmm
a is aluminum U channel
b is a flanged bearing
is your output shaft
g are the gears
m is the motor
| is the motor output shaft
w is a wheel collar to keep the bearings held in place
now a trick here is you can fix the aluminum on a drill press and drill both bearing holes in a single pass. first you need to score a centerline so you can put the motor on the same center as the shaft. then drill the holes for the bearings slightly undersize and use a reamer to open the holes to a real snug fit on the bearings. now print the mounting pattern for the motor on some paper and use it as a template with a centerpunch to mark where to drill the mounting holes for the motor. make the holes just large enough to clear the threads of the motor mounting hardware. install the motor to the bracket, put te pinion gear on it but leave it loose, press a bearing onto the shaft leaving 3/8" or so on the flange side, put the flange+shaft assembly into the bracket putting it through the other bevel gear in the middle, press the other bearing on the shaft (support the shaft not the bracket), add your wheel collars, align the bevel gear and pinion and tighten them up, voila r/a gear drive on the cheap… well cheap not considering the parts came from sdp-si… but you got the idea.
hopefully that made enough sense to follow it. I’ve got a hot date with some tax forms at the moment though so I’ll let ya ponder it and check back later.
After much debating (20 seconds) I have decided to go with your idea. I was gonna do something like this
p p
bp g pb
wbp-----g-------- pbw---
bp ggggg pb
p | p
mmmmmm
momomo
momomo
momomo
momomo
p = pillow block
mo = motor
m = mount
everything esle corresponds with your drawing
I was going to mount all that on a single plate to make it 1 piece, but you’re idea is 1) cheaper. 2) Much simpler
I just happen to have some aluminum channel from my canabalised BRAT and some 4 mm bearings from my track kit. The bearings fit perfectly, and if I am right, the motor sctually lines up perfectly with the SES holes (1 big hole with 4 smaller orbital holes) lynxmotion.com/images/data/pghm05.pdf (the motor mounting holes)
the only issue I have with the aluminum channel is the fact that it might be hard mounting it to the bot unless I squished a motor mount between the channel and the face plate of the motor and also latched the side of the channel onto the side of the bot, who seems like it would be a fair hold, assuming the motor shaft is long enough to reach that far.
So right now here are the plans:
Order gears and aluminum channels.
Make sure everything fits.
Buy drill press. underlinesImportant
Think 4 of the PGHM-05 motors will pull a 4-6 lb treaded bot around? I think they will…
PS. Apparently I can’t draw for crap. You can put it together yourself. You build robots.
Assuming that all goes to plan with those gear boxes I went ahead and did some doodles in school today. I have been thinking of how I can put a suspension system on it after I can get the rover moving with just normal direct drives. Here’s a quick sketch of what I want to do eventually.
Basically I ripped the design off of an RC car suspension arm. With a few modifications to that design and a couple dogbones with couplers I think it’s be possible. Each track ywould be in it’s own contained pod so there would be no issue of holding them together. The only problem I have really seen so far is the fact that the whole track will move up and down as one, rather than have a twisting effect where the front and back can move without having a huge effect on the other. If you guys think the design will work so far let me know. I want to be able to further this design and get some real measurements and figures going.
Another drawback is how far the power has to go, whether or not that will have a truly noticiable effect on the power I’m not sure, but I think with 2 of those motors on each track it should have plenty of power.
. ah well. I also plan on picking the shafts I need there. Depending on my next pay check I should have the gears within a couple weeks
