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Got a new toy

1176 Views 7 Replies 4 Participants Last post by  Saviour
I have gone out a bought a 'DPT' for them that do not know what they are. It's 'DIGITAL PHOTO TACHOMETER'.
Been looking for one for some time now, but just got around to buying one.
As with most things of this nature, we first need to know if it is accurate. So a quick test against a known 100% good one will give us that answer. Off to play with M97. She will know, 'SHE' is always right ;-) @ 1000 RPM on M97, I get 1000 RPM on the DPT, on to 2000, again, DPT reads 2000. @ 3K, DPT reads 3k and so on up to 6,000 RPM and DPT reads 6,000. Cannot go higher than that. M97 only revs to 6,500 RPM. So I think the DPT is good for go. (Could be way off at 20,000, but don't tell him).
I have done this sort of testing before. AC 16V PSU, connected to LED's to get a strobe effect. DISCO time again Folks. Black and White disc. Disc should stop at 3,600 then again at 7,200. at which point you take a voltage reading. lets us say 3.7V at 7,200RPM = 12/3.7*7200=22918rpm. You get the idea.
Most motors you have the reading printed on them. MABUCHI, please take note, and others.
Now onto the DPT, AC reading in RED.

So, there you have it. Some not far out, others way off.
Comment, Please.
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QUOTE (TR7_Driver @ 5 Jun 2011, 18:10) <{POST_SNAPBACK}>Have you got a picture of the DPT in use, also if you don't mind me asking where did you source it from.

The Bay of pigs. I'll PM you with details. he has dropped the price since I bought it.
QUOTE (Screwneck @ 5 Jun 2011, 18:27) <{POST_SNAPBACK}>Eh?

Red means one thing, so what's the black mean?

Does the Taco come with sour cream and refried beans?

As it happens, YES. we had that for dinner last evening, with a few 49ers.
The Black means another thing, as opposed to one thing. Or, the black number to the right are from the Tacho, and to the left from the motor. the dif is from motor - Tacho, or it could be the other way around. Tacho - Motor. Hope that helps.
And more advice, then please see my Psychiatrist.
QUOTE (300SLR @ 5 Jun 2011, 19:48) <{POST_SNAPBACK}>One figure that looks a bit strange
the 4th motor down seems to be a 18k "Hornby2" pulling over 56k at 12 volts
or have I got the wrong end of the stick somewhere?

Yes, very. The 56K was done with the AC strobe and calculating as above. The Tach shows a whopping 38,557 though.
There is another motor that's way over odds.
9072 in a T260, (10th down) cals with AC gave 45k, I could not keep the disc on for the Tach test, so left it at 30k. Bought the motor off the bay of pigs for a £1. Does seem to run more like 40K than 30K. Fitted to a VMG T260 just for the hell of it and are next meet has a CanAm race. Just hope the car is not to wide for the track.
The one motor that stays true to form. The Fly F40 Scorpion. only 84RPM off the makers figures. All of you that have this motor will know what I mean. I would like to get my hands on a few more for scratch building.
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