Author Topic: Tachometer design for small engines?  (Read 1754 times)

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Offline larryblTopic starter

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Tachometer design for small engines?
« on: July 17, 2016, 01:23:58 am »
This may be a simple matter-or not, but I have not found a good solution to a problem I have, and as a member of several Tractor sites no one there has a good solution either. The machines that I restore run optimally at 3600 rpm, and setting the rpm is challenging. What I need is a Tachometer that can be installed on the dash and 1. Looks good in/on the dash (dash pictures attached), and is weather proof. 2. Simple to hook up. 3. Works off 12-14 vdc WITHOUT an internal battery. 4. Will need some sort of mechanical or spark pickup as some machines are twin cylinders, some single, Also some use points and coil, and others use electronic ignitions.

I have looked at the tinytach and it seems the internal battery is less than desired.

I use this to set the initial Governed setting at 3600 rpm, but there is no way to monitor actual rpm when the machine is in use.

I am capable of assembling discrete components. I guess I am looking for a display that can be stuck to the dash, some sort on counter that can display revolutions, and some sort of mechanical / optical pickup that can be added to the flywheel or drive pulley on these machines.

I am not against some sort of “spark sensor” as the tinytach uses.

I have some electronic experience and can assemble discrete components. I have converted several of these machines to use LED lamps, Including one that requires 28 vdc which I taped the 30 vac stator to obtain.

Just looking for options or suggestions.

Pictures of the machines that I am talking about.
1978 Roper 20T
1988 Craftsman II
1990 Craftsman
198? John Deer (In the works)
Any suggestions?

Offline tautech

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Re: Tachometer design for small engines?
« Reply #1 on: July 17, 2016, 02:13:42 am »
In another life I serviced small motors and tachos ever since have been of interest. AFAIK currently the best portable unit for use as service/tuning/setting max revs aid is the Husqvarna digital RF unit, but oh the price.

For setting max revs something that is fast to give a reading is best, and a non-contact RF or inductive pickup is best.
There are a few on Aliexpress, some quite well priced that might be worthy of consideration however a different brand that I got was very slow to measure max revs in chainsaws that run to 13K RPM.

This seller has a good range and models for 2 & 4 stroke, 1 & 2 cyl engines
« Last Edit: July 17, 2016, 02:23:14 am by tautech »
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Offline Seekonk

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Re: Tachometer design for small engines?
« Reply #2 on: July 17, 2016, 11:32:51 am »
I got a friend a couple $12 US ship ones that look the same as the Tiny for his gocarts.  He loves them.

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