Journal wowbagger's Journal: Good source for gears? 8
I'm looking for a good source for some gears.
Background: I have several antennas on my tower, for various purposes (wideband receive, VHF omnidirectional, VHF directional, HF, etc.). I'd like to be able to switch those onto my radio as desired. Now, there are remote controlled antenna switching boxes out there, but:
1) Most of them are for HF only - not VHF. This is because
2) Most of them use relays to do the switching, and co-axial relays to switch VHF and UHF get VERY pricy.
3) Notwithstanding the use of cheaper HF only relays, most of those switch boxes are DAMN pricey.
Now, compare that with the cost of a simple antenna switch like an MFJ-1702. Simple, relatively inexpensive, good through UHF, good isolation, and not very expensive. However, it is a manual unit, so I'd either a) have to run down to the basement where all the feedlines enter the house and switch it there or b) run all the feedlines into my operating station.
What I want to do is set up a simple gear drive on an MFJ to select the antenna - I'm thinking something like a 3 inch diameter gear on the box, a 120 RPM or so gearbox and motor combination driving the gear, a couple of optical interruptors looking through holes in the gears to provide position sensing, and I should be able to make a switchbox that would do the job. Heck, done right I don't even think it would need much more than a couple of relays and transistors to control it - no microprocessor needed.
But I am having a time finding gears that would do - again, what I'd like would be a gear, preferably metal, about 3 inches in diameter. Anybody got any good sources?
Pulleys? (Score:1)
Couldn't you use pulleys and a tight belt instead? Pulleys are much easier to find..tractor supply, graingers, etc
with that said, any generic junkyard will have old rear ends and manual transmissions. When they are officially broken, they are cheap, but usually not much is really broken in them either... Open them up, tons 0 gears/bearings/shims and whatnots...
Re: (Score:2)
I've never pulled apart a transmission or differential, but it seems to me those gears would likely be larger, heavier, and likely more coarsely toothed than I would like for this task - but I will keep it in mind.
maybe look then... (Score:1)
...where the robotics [google.com] researchers get their parts. I have no idea there, but fine tuning it down to size etc is probably easier there than the junkyard, and the precision will be better no doubt. Hmm, old VCRs have some fine toothed plastic gears in them and motors, etc. And old printers for that matter.
All Electronics (Score:2)
Has some gears and sprockets here [allelectronics.com]. Doesn't look like any metal gears at the moment.
They may not have what you are looking for now, but they get new stuff all the time. Worth checking now and again.
Re: (Score:2)
Thanks for the link - that looks to be pretty close to what I want. I'll think about it more and see about making my order.
Update: found somebody interesting (Score:2)
The bad thing about Google is that it is too easy to drown in chaff and not see the wheat.
I found another place: Servo City [servocity.com] - that looks promising.
Servo seems more like what you want... (Score:2)
I'm late to the party, but it seems like a Servo (which it looks like you've found), or a solenoid and a lever system, or a stepper motor would be better than dealing with a bunch of gears and motors.
Re: (Score:2)
For this application steppers aren't a good fit - you'd have to have the drive electronics to generate the sequencing, and the critical thing to control (position over detent) wouldn't be as easily controlled by dead reckoning as it would be by a simple optics and interrupter - which can then be used to control a simple motor more easily than a stepper.
As the switch has more than 2 positions (ant1, ground, ant2 for the model I quoted, although I'd actually use one of the 4 antenna models) a simple solenoid