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Topic: how do i make a gear box? (Read 3529 times) previous topic - next topic

twirap

I have never done this before...I know what gears I need and I have some aluminum plating but I dont know how to put the gears on the aluminum...Any ideas?

Also, I am kinda noobie to batteries so all batteries seem same to me except their voltage and current output so how do i know which battery i need for long lasting or which battery can provide me with more voltage and current with minimal weight?

woody_unreal

Im by no means a expert on any of those subjects but, gears are a bit tuff to just make from scratch, and as far as the batteries, alot depends on what your doing, current draw,time total time, things of the nature . So there realy isnt going to be a straight foward answer. So maybe a little insight into your project may inlighten us :)

twirap

ive got a wall climbing robot and i need power source for it and so i need some light weight batteries that dont weight so much and arent super expensive..How do people normally make gearboxes? If ive got gears how do I put them together to make a gear box im having trouble figuring out how to get those pin thingies and then how to connect the pin thingies to the surface as well as gears..

Grumpy_Mike

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i need power source for it and so i need some light weight batteries that dont weight so much and arent super expensive.

Yes and the rest of the world wants that as well. Try a polymer film, not cheap but fits the bill for the other things.

Gears can be laser cut, water jet cut, or cut on a lathe depending on the sort. They are not normally hand cut. It depends on what the gear is connected to but normally a solid axle is used either side of a bearing to get the power in and out.

twirap

I will look into polymer film. I dont mean create gears myself. Say I have 5 gears but now I need to put them together to make a gear box...these gears are just parts how do i put them together?

marzetti

Building gear trains can be quite difficult if you don't have machining capabilities. I would look around for existing gear modules which can be found in any number of cast-off electromechanical devices such as printers, optical drives, copiers, etc. There are also a number of small gearboxes available from various robot parts vendors on the web that are designed for attaching to small motors. Another option that is much easier for DIY fabrication is using timing belts. The belts and pulleys can also be salvaged from printers, scanners, etc.

retrolefty

#6
Mar 24, 2012, 07:14 pm Last Edit: Mar 24, 2012, 07:17 pm by retrolefty Reason: 1
Both designing and building a gear box and selecting the optimum battery is best done by starting with applying the proper mathematics to determine the specifications required to perform the stated task. Lots of rework will result in just guessing at what the results might be for a given random design. It should first start out as an engineering effort and only when that is completed does it phase into a construction effort.

Lefty


DuaneB

Hi,
   For lightweight batteries I would suggest LIPO batteries, lots of power in a small and light package. Its what we use in RC Race cars, boats and aircraft, lots of power, good run time, reasonable price and lightweight.

For gearboxes, it depends on your load, but as others have pointed out, the robot shops will have a wide choice of gearboxes that can often be built in different configurations to suit different applications. Belts are also a good suggestion, most competition orientated on road RC Race cars are belt driven these days so there are a wide range of belts and pulleys available in the model industry, these will support moderate loads. If you really want to 'roll your own' gearbox, belts will be so much easier as you just need a single pulley or roller to set the belt tension rather than having to deal with precise gear mesh on multiple axles.

Duane B

rcarduino.blogspot.com

Read this
http://rcarduino.blogspot.com/2012/04/servo-problems-with-arduino-part-1.html
then watch this
http://rcarduino.blogspot.com/2012/04/servo-problems-part-2-demonstration.html

Rcarduino.blogspot.com

twirap

Thank you all! Thank you for the LIPO batteries. Also, I have access to university student machine shop so I can use that. I should probably get me a thick sheet of aluminum and stick the gear on there and pin a needle or such through it to keep it in place.

twirap

One last question...I know you can put a circuit in series and the currents add up, if you put circuit in parallel the voltages are same...


If I have say a battery pack which gives 3.2 volts and 1.5A and 5 servos, how can I make it so that all the servos share the same battery pack GIVEN that I will not be using more than 1 of the servo/motor at 1 time? I just learned in one of my classes about Tri-state buffers and that seems like it would be useful here but what is a simple solution to this?

Grumpy_Mike

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how can I make it so that all the servos share the same battery pack

Just wire them up to the same power and ground.

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GIVEN that I will not be using more than 1 of the servo/motor at 1 time?

If you don't power a servo it can be moved so even if the motor is not turning it needs to be powered.

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I know you can put a circuit in series and the currents add up,

No with components in series the current through each component is the same.

twirap



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GIVEN that I will not be using more than 1 of the servo/motor at 1 time?

If you don't power a servo it can be moved so even if the motor is not turning it needs to be powered.

I know that because you need to provide the power to maintain its position

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I know you can put a circuit in series and the currents add up,

No with components in series the current through each component is the same.
[/quote]

I am sorry I really suck at expressing my thoughts...what I mean was if you have a bunch of current generators the current through the whole circuit is the super position..


since the servo uses power to hold its position cant I block the power for some time and provide power to the other servo (I dont care whether the unpowered servo holds position or not)

Grumpy_Mike

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cant I block the power for some time and provide power to the other servo (I dont care whether the unpowered servo holds position or not)

Well you could remove the power with a top switch like a p-channel FET but you then have the problem of being in the situation of applying an input to an un powered device. This might cause latch up, damage, or be perfectly fine depending on the electronic design of the servo. I suppose you could always switch the output driving the servo to an input just before you removed the power but that might cause it to twitch.

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what I mean was if you have a bunch of current generators the current through the whole circuit is the super position..

of a number of circuits where all but one current generator is replaced by a resistor of the same value as the generators impedance, yes, but that same current goes through all the devices.

keeper63


Also, I have access to university student machine shop so I can use that.


If you go the route of using the machine shop, please, for the love of mike, take a class on using the machine shop (if the shop is smart, they will -require- this). Machine shops, machines, and tooling is not something you "play" with. You can't just go in and expect to easily figure it out. It can be dangerous; you need to understand and respect what you are doing. One slip-up, and you can lose a finger or worse.


I should probably get me a thick sheet of aluminum and stick the gear on there and pin a needle or such through it to keep it in place.


You probably don't really need that thick of aluminum; you could even build your gearbox with acrylic or other lightweight plastic (like sheet styrene or sheet ABS). Have you ever taken apart a cheap toy with a sheet metal gearbox (maybe they don't make 'em that way today much; probably all molded plastic nowadays). Anyhow, thick aluminum is not needed, unless you expect to put a lot of strain on your gears (and if the gears are plastic, they'll fail long before the frame of the gearbox).

Your idea, though, to prototype the gearbox is a good one, though - especially if your gears are "random ad-hoc" piece where you don't know important things like pitch-circle sizes and whatnot...

So - get some cardboard, or sheet styrofoam, or even foam-core board; use wood dowels the size of the shafting for the gears, and poke the dowels into the board where you need the gears. Use pieces of cardboard, etc to act as "spacers" if you need to "stack" the gears. You might want to rough out placement and such on some graph-paper first (or paste graph-paper over the top of the prototyping substrate you are using - you might even consider printing something like this up, at a known DPI spacing, for later measurement purposes). You want your gears to mesh tightly, but not so tight that they will bind, and not so loose that they will slip under stress, which will just wear the teeth. Mounting the motor with it's pinion gear will be trickier, but doable (maybe a drop of ink or something on the end of the shaft, and press it on the paper to make a mark?)...

Once you have your prototype laid out, you can transfer the measurements/positions to another template paper or something, or scan it in at a known DPI and clean it up to a template to paste onto your sheet metal. Then mark the locations for shaft holes and such on the sheet metal with scribes/punches, then use a drill press or such to drill it out for the shafts (make sure you clamp the metal when doing this - DO NOT TRY TO HOLD IT WITH YOUR HANDS). Mount the shafts with solder (steel or brass shafting only) or epoxy. Or, if the shafting it long enough, use a die to cut threads and mount using nuts on either side.

That's the real basics. This isn't to say it will be easy, or it will work correctly the first time out. If this is your first time doing anything like this, it will probably be better if you looked for an off-the-shelf gearmotor solution first.
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

jwatte

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You want your gears to mesh tightly, but not so tight that they will bind, and not so loose that they will slip under stress, which will just wear the teeth.


Generally, you want to mount gears so that the center distance is exactly the sum of the pitch distance of the two gears. (This may be modified if you do profile shifting in your gears, but that typically only happens if you custom design the gears for special use cases)

Drill presses and slit shears and lathes and vertical mills are all nice tools to know how to use -- but if you want the simplest option to get your machine working, I hope your shop has a CNC mill. Once you draw out the various pieces (axles for gears, mounting frame for motor, etc,) then you can transfer the exact measurements to a plan that you can save out as instructions for the mill.  Don't forget to make room for bearings or bushings for your axles. The mill will then make the appropriate holes in your metal (or plastic) with very tight tolerances (usually better than 1/1000th inch.)

You will still need to learn the basics of machining -- feeds and speeds, material properties, end mill types, etc -- as well as safety! But at least the CNC will do the "touchy feely" parts of getting exact measurements right, rather than you trying to hit the spot with a drill press and a wobbly drill bit.

Or just find a laser cutter and cut out the pieces you want out of acrylic or acetal or something. Easier to work with, but doesn't do metal :-) (Well, unless your cutter measures in the kilowatts... ;-)

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