CH Ignitions

My Feedback: (11)

Hello everyone, I need your help to locate a small thrust/dyno stand.
I found it like a month ago and I thought that I saved the link.
Stand is made/sold in USA and outfit is located north-east USA. VT,MA,CT; in one of this states.
They have two versions price between $150-$190.
Stand is made of wood, it has a custom digital "scale" that if I remember correctly it display HP or thrust can't recall correctly.
The engine has a wood mount and is mounted on a round ...."stick" that goes on the back where the scale is.
Also on the back it has a half cerc that has a scale engraved on to it . When engine is running it pulls on the digital scale and if you pull the tab...on the back it unlooks the round shaft and let it to rotate on it's axis and gives you the the second reading on the wood half for torque.

I am hoping that any one else seen it/have it and can provide some info.

Thank You
Adrian

Lnewqban

Not what you are asking, but good related reading:

http://modelenginenews.org/techniques/testing.html

CH Ignitions

My Feedback: (11)

Thank You,
I still not find it, I can not accept the fact that I seen it and now I cant find it anymore. Drive nuts( not that I was diffrent before).
Istill hope that someone has one, seen one.

Adrian

JohnBuckner

My Feedback: (1)

Well I do not have one but there have been a few different ones over the years and most do not last long in the market place.

The most recent seemed to be about ten years ago and there were two different units. One was an actual dyno that measured torque and the other was a sliding spring affair that read direct thrust.

If I am correct both were well made and were constructed mostly of hard wood.

I too would love to pick up a pair of these nifty tools.

John

CH Ignitions

My Feedback: (11)

Yes John,

that is what I seen, most wood from what I seen in to the picture, But this unit had both in one, Thrusthad digital display and Torque a ...needle type scale.Seen it less than a month and was around $180 I think.
Hope some one has a link for the site.

Thanks
Adrian

airbusdrvr

After reading this thread, I have a question. Of what practical use is knowing the torque value of an engine? It would be fairly easy to make a motor test stand with a roller/track mount and attach a scale to see static thrust. Were I able to ascertain the torque value, what would I do with this info?

bogbeagle

You can use the torque value, coupled with the rpm to derive horse-power. That's handy to know, especially when it bears no relation to the manufacturer's quoted figures!

Lnewqban

What about this one, Adrian?

AMERICAN HOBBY PRODUCTS
12 West Hill Circle, Reading, MA 01867
Dyna Torque Test Stands to measure torque and HP on engines from .049 to .90 - $129.95
Thrust Finder to measure propeller thrust in pounds and ounces up to 15# for engines from .10 to .90 $124.00 Phone: 781-944-8316 Fax: 781 944-3585

http://www.clcombat.info/dyno.html


Regarding the measurement of Horsepower and Torque of engines and its practical use:

"These two concepts are interrelated but distinct. One horsepower is the force required to lift 550 pounds 1 foot in 1 second. Note that horsepower refers to work done over time. A 10 hp chain saw should be able to do more work than one which only develops 5 hp. Torque, on the other hand, refers to the twisting motion on the crankshaft. It is measured in foot-pounds; one foot-pound is a force of one pound exerted on a one-foot lever. Torque, therefore, is a measurement of instantaneous force and does not contain any concept of time. You can understand the distinction between these two terms with the following example: two vehicles weigh the same and have identical horsepower and gearing. Both ought to reach the same top speed. But the one which develops greater torque will reach that speed sooner. In industrial applications, torque shows up in the ability of the engine to accept loads without bogging down and losing rpm.

Torque can be related to horsepower by assuming that the twisting force acts on the end of a one-foot crank. The force would act over a distance of 6.28 feet—the circumference of a circle with a radius of one foot—with each revolution of the shaft. If you know the load, and the rpm, you can easily calculate the foot-pounds of work per second. To get the horsepower, multiply the rpm by the torque and divide by the constant 5252.

Slide rule calculations enable engineers to estimate horsepower with some accuracy, but the test is to mount the engine on a dynamometer, a device which can accurately load the engine. The load may be a friction brake, a generator, or a water turbine. The latter two are most commonly used because of their precision. Normally, the engine is mounted in a flexible cradle connected to a spring scale. As the crankshaft turns, it will exert an equal and opposite force, twisting the cradle in ‘the direction that is counter to the direction of crankshaft rotation. Torque is then read directly from the scale.

The load is adjusted to hold the engine at a given rpm with the throttle open. Then the load is reduced and the engine speed is increased to the next test point. Fifteen or twenty tests across the rpm scale provide enough data to plot torque and horsepower on graph paper as a curve."

Copied from
http://www.house-projects.us/small-g...eration-0.html

JohnBuckner

My Feedback: (1)

Outstanding Lnewqban, Those are definately the two units I recall most recently and here is the current web site for American Hobby Products:

http://bj-model-engines.com/American...ustfinder.html

I hope they are still operating and will call them when I wake up this morning.

To answer the question someone asked "what practical use is knowing the torque value of an engine" And "what would I do with this information" is simply who cares? and I would probably use it to settle some old some old bets with my buds about which of our pet engine were the most powerful.

This hobby is all about the learning and when the learning stops you are dead in the water and so far its kept me going since the fifties with always something new to learn. Thats why I am sorry I did not order these when I first became aware of them.

John

airbusdrvr

The torque/horsepower is all "nice to know," but still not all that useful. When we build a plane, it is usually designed for a certain size motor. We then take that size motor and try several different props to see which gives us the best thrust or rpm and go with that prop. It is "nice to know" the torque but I still don't see how this info is really useful.

airbusdrvr

JohnBuckner, now that is the type info that would be useful. Thrust is, afterall, what we are looking to optimize with the prop selection.

airbusdrvr

JohnBuckner, on the same website you listed above is a link to a dynamometer for small engine, http://bj-model-engines.com/AmericanHobby/Dyna.html . That would give the info the i7x58 was asking for.

JohnBuckner

My Feedback: (1)

Like I said I don,t care if any of it is useful to anyones else's standard. It is useful to me in keeping the learning and me alive.

Yes I think the original posters question was well answered (thanks Lnewqban for the link)

And yes those are the units that were mentioned in my first post, The Dyna Torque and the Thrustfinder.

John

CH Ignitions

My Feedback: (11)

It is a such beautiful day when you wake up and find your answers. I can not thank you guys enought for all the feedback.
John that is exactly what I seen close to amonth ago and I could not find it any more. I did several conversion on saito engines from glow to gas and I wanted to check the output power. glow vs gas. I was thinking to build one but ...if the wheel is invented ...why should I reinvented.
Now that is been found ...I seen that they are out of it. I will call after the holiday to see when will be available, if will be to much time...then second option will be to build one and use a ...fishing scale, that will do the job, I use it before.

Or.... let's try to come up with one . Ihave couple ideas, need to put them on the paper and build a test unit. Let's make couple designs and post them up and try them. let's make one unit that will do both....with 2 fishing scales, seen them on ebay for less than $8.


Thank you all
Adrian