1931stdcoupe
Junior Member
Has anybody successfully used a hand held non-contact laser tachometer to measure engine rpm? If so, where do you put the reflective tape?
Tachometer to measure idle rpm?
- Thread starter 1931stdcoupe
- Start date
1931stdcoupe
Junior Member
That's true Alex, but that's a good place to get your hand chopped off!
Any alternative tachs out there for checking idle speed? I dont have enough experience yet to know by ear....
Any alternative tachs out there for checking idle speed? I dont have enough experience yet to know by ear....
katy
Well-known member
Don't try and put the reflective tape on when the engine is running.
The hand held unit doesn't have to be close to the reflective tape to work. Give it tryers and you'll find out if it will work or not. Simples.
alexiskai
Well-known member
Yeah the dominant way to measure rpm is inductively, either using a mini-tach, which has a wire that wraps around the plug wire, or as one function of a digital timing light.
I've never used a laser tach for engine rpm, I've used a timing light, but the timing light also involves pointing a device at the crank pulley and I've never lost a digit doing that. I have used laser tachs for other things and you could hold it far enough away from the pulley that there's no danger (and still get an accurate reading).
I've never used a laser tach for engine rpm, I've used a timing light, but the timing light also involves pointing a device at the crank pulley and I've never lost a digit doing that. I have used laser tachs for other things and you could hold it far enough away from the pulley that there's no danger (and still get an accurate reading).
Keith True
Well-known member
I've used a laser tach with reflective tape for years.Not so much on car engines,but figuring speeds of shafts to rig up sawmills,edgers,planers,debarkers,apron chains,hydraulic pumps,chippers,grinders,etc.I used a cheapo tach,it works fine.I thought I had to buy special reflective tape,turns out plain old white tape would work.
P.S.
Well-known member
I use a tach made for measuring RPM of a model airplane propeller. Assuming you have a 2-blade fan, just hold the tach a safe distance behind the fan pointed forward toward the radiator. Tach shows fan RPM. If your fan has about the same inside diameter pulley as the crank, no math skills required. My fan pulley ID is a few % larger diameter than the crank pulley, so I add 20% and call it good.
1931stdcoupe
Junior Member
I know that it would be impossible and dangerous to try to put reflective tape on a running engine Katy! I just didn't know if you would have to get too close to the spinning fan to use a laser tach...