Single cylinder tacho???

Submitted: Monday, Mar 27, 2006 at 22:43
ThreadID: 32236 Views:4415 Replies:8 FollowUps:7
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Hi all, I'm building a generator/ compressor combo and I am using a single cylinder stationary engine of about 4HP to run it. I would like to hook up a tacho to it but where do I find one for a single cylinder engine?
That's my question now here are the details: We occasionally need compressed air and/or a 12volt generator on trips. I have used an air conditioning compressor as an air compressor for many years on my old truck but on my new one I don't have diff locks ect so it's use is more limited and I would prefer to have something that is not in the engine bay. I have an electric compressor but nothing pumps like the air con pumps. The 12 volt generator will simply be a Bosch altenator and will be used for those times when a drive of an hour or two is needed to top up the batteries or some one gets caught with a flat battery but won't be for direct jump starting. The tacho would help optimise setting the revs for each application. The whole lot sits on two small air cylinders under the motor ect. It is reasonable in size measuring L500mm X W250 X H 450. The idea behind this project is to use it as a back up unit. It will cost me virtually nothing as I have a great little 4 stroke motor, altenators and compressors, most of the gauges and bits 'n' pieces I need and a lathe for the machining so it's a project come something to tinker with in the garrage. I have also made a very good (read quiet) muffler for it. I have geared the altenator up about 5 to 1 and the comp down about 3 to 1. I haven't run it yet as I still need another day or 2 to finish machining up the pullies. Any CONSTUCTIVE ideas would be most welcome. Cheers.
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Reply By: V8 Troopie - Monday, Mar 27, 2006 at 23:50

Monday, Mar 27, 2006 at 23:50
Well Stuart, it looks like you are a bit of a tinkerer, like myself LOL.
That tacho request has me intrigued, you really don't 'need' a permanently hooked up one for the gadgets you are hooking up to the motor. So I guess you would like to use it just for setting up purposes as you mentioned. In that case you could use an optical tacho on the flywheel. These are quite useful for other whirring wheels as well. Where to get one? Try the modelling shops, optical tacho's are used on the little model IC engines. I believe they are not too expensive these days with the price of electronics going down all the time. All you need to do is stick a strip of white tape to the flywheel to use these tacho's.
Be warned though, fast running machinery appears standing still under the strobe light - keep the fingers away.
good luck,
Klaus
AnswerID: 163335

Follow Up By: Stuart - Tuesday, Mar 28, 2006 at 00:31

Tuesday, Mar 28, 2006 at 00:31
Hi Klaus, Point taken about being permanently hooked up and I had thought about one of those but even wholesale they are about $55-60. I was hoping I could modify/ trick an existing one. However like you say, it could come in hand for other stuff.
Will probably go that way if I get no other ideas. The handbrake wouldn't be to keen as I always seem to be spending money on some sort of tool and she still remembers how much I spent on the lathe even if it was a bargin. A tinkerer's life is never easy but it is fun.
Cheers and thanks.
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FollowupID: 418079

Reply By: Richard Kovac - Tuesday, Mar 28, 2006 at 00:18

Tuesday, Mar 28, 2006 at 00:18
Stuart

Use the "w" terminal on the Bosch alternator it sends out hz any electronic tacho should run on it

I think

Richard

No thats what the "w" does
AnswerID: 163340

Follow Up By: Stuart - Tuesday, Mar 28, 2006 at 00:38

Tuesday, Mar 28, 2006 at 00:38
Thanks Richard, that's something I had no idea about but I will have a tinker with it. You realise now of course that in solving? that problem you have created another. For that to work I will have to sit and work out exactly how far I have geared up the altenator. Like I said above, a tinkerer's life is never easy but it is fun.
Cheers Stuart.
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FollowupID: 418080

Reply By: Bob Y. - Qld - Tuesday, Mar 28, 2006 at 05:40

Tuesday, Mar 28, 2006 at 05:40
Stuart,

Small tachos/hourmeters are available for motorbikes etc. Have a LCD readout, and are run by a button cell. Get their pick-up from a wire wrapped around HT lead to plug. We've had some here, but no longer fit them, bit small to read easily, bouncing across the downs on a motorbike.

Try a good bike place, for starters.

Hooroo...
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AnswerID: 163362

Reply By: Ray Bates - Tuesday, Mar 28, 2006 at 10:30

Tuesday, Mar 28, 2006 at 10:30
Yes I remember that when I worked on large static diesel generators I used a strobascope to get the revs right. It was a very usefull tool and enabled me to get all things at the right revs. If I didn't the engine would either have been motoring (being driven by the other engines) or it was impossible to sinkranize the engine on the "board" with the other engines.
Just my two pennerth
AnswerID: 163400

Reply By: Ray Bates - Tuesday, Mar 28, 2006 at 10:31

Tuesday, Mar 28, 2006 at 10:31
Could a motorcycle manufacturer help you?
AnswerID: 163402

Reply By: traveller2 - Tuesday, Mar 28, 2006 at 14:02

Tuesday, Mar 28, 2006 at 14:02
Get a Tiny Tach from www.tinytach.com they will sell direct if paying with a credit card. I got one for my V8 diesel and also have one on a single cylinder GMC genny.
AnswerID: 163443

Follow Up By: Stuart - Tuesday, Mar 28, 2006 at 20:41

Tuesday, Mar 28, 2006 at 20:41
Thanks Traveller2 I will give them a try. I have also been told that a tacho off an old single cylinder motor cycle should do the trick as they work like an induction timming light off the magneto. Also the people above have given me the same path to try.
Thanks everyone for your help.
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FollowupID: 418231

Reply By: bombsquad - Wednesday, Mar 29, 2006 at 15:48

Wednesday, Mar 29, 2006 at 15:48
Doing something similar myself. what rev range should the alternator spin at??? (bosch self regulating out of an old holden)

Cheers Andrew
AnswerID: 163663

Follow Up By: Stuart - Friday, Mar 31, 2006 at 10:35

Friday, Mar 31, 2006 at 10:35
Hi Andrew, I received this response from Collyn but I couldn't see it on the thread. Hope this helps. Alternators are designed to give about 70% of their output at 4000-5000 (alternator) rpm. Safe to run most of them as high as 15,000 - but there's not much increase beyond 8000.

If you need more specific data contact me directly.
Collyn Rivers
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FollowupID: 418879

Follow Up By: Stuart - Friday, Mar 31, 2006 at 10:40

Friday, Mar 31, 2006 at 10:40
Hey Andrew I forgot to ask, what are you driving the altenator with and are you setting up a compressor as well.
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FollowupID: 418880

Follow Up By: bombsquad - Monday, Apr 03, 2006 at 16:03

Monday, Apr 03, 2006 at 16:03
Its a small 2 stroke motor that pulls around 9500rpm with no load. I will have to come up with some form of direct coupling that can handle that rpm, probably one off a hydraulic motor. It will be noisy, but will only be used as an emergency, or set it up with an hour or so's fuel in it & go fishing etc - only on secluded campsites as not to annoy anyone! Its not something I don't really need, but it is a really neat little engine I picked up at a clearance sale at a property for $5.00, and had an old alternator lying around anyway.

Cheer Andrew

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FollowupID: 419470

Follow Up By: Stuart - Monday, Apr 03, 2006 at 21:08

Monday, Apr 03, 2006 at 21:08
Hi Andrew, let me know how you get on. On my first attempt I used a 26cc wipper snipper motor and had it direct coupled. It spun the altenator OK but when I applied a load to it the motor would stall. Not enough grunt. That's why Christie Engineering use a 50cc 4 stroke I guess. It made a hell of a racket as well.
Cheers.
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FollowupID: 419531

Reply By: bob&loz - Monday, Apr 03, 2006 at 21:45

Monday, Apr 03, 2006 at 21:45
go karts use small tachos the real cheap ones just run of the ht lead. you might pick one up on ebay or trading post
bob
AnswerID: 164632

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