Author Topic: Tractor PTO rev counter  (Read 2859 times)

Offline pycoed

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Tractor PTO rev counter
« on: October 20, 2020, 09:05:58 AM »
Main rev counter on my Zetor 7045 is a bit temperamental & sometimes on a cold morning doesn't register for a half hour or so. This is not usually a problem , but I've recently resurrected a Japa 100 buzz saw which needs to run at a specified PTO speed (400 rpm). 
  Mindful of flying tungsten carbide inserts from the saw  :bugeye: , I thought I'd better try to get a better rev readout.

You can buy digital rev counters complete with a magnetic pickup sensor & neodymium magnet for around 8 online. I'd previously used one on my Kubota engined Cushman Truckster which didn't have a rev counter cable. Rev counter worked fine, but I found that 400RPM on the PTO was less than 1000 rpm on the engine, at which speed the Kubota produced about 4 hp & the saw could be stalled on a toothpick :bang:, hence the decision to use the tractor, at least until I can find/make/bodge a reducer box for the Cushman PTO.

Found a bit of ally plate about 3/8" thick & turned a hub out of some ally bar & pressed the two together, drilled & filed to fit over PTO splines ( a complete waste of time actually - if I do this again, I'd just make it a slide fit over the splines), drilled & tapped for a couple of grub screws to hold in place & drilled & tapped for the magnet in the outside edge. Bent up a bit of steel strap to hold the pickup & fitted to one of the PTO guard bolts. 

I had a plastic knockout box lying around , so fitted the Digital revcounter to that along with a switch & mounted on inner wing. There was a convenient permanent 12v feed just near the handbrake so I used that with a switch to energise the setup, rather than run an ignition feed back from the dash .

Wiring these is dead simple - it's just +12v, earth & the sensor feed to the readout. Sensor pickup comes with three wire leads , again +12v , earth & the sense wire (these are brown, blue & black for the line, earth & sense respectively on the the two sets I've used.
Now I have a buzz saw & also still my front teeth