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Sep 13, 2019, 03:28 PM
BOYCOTT SCAMAZON
lectroglide's Avatar
Thread OP
Discussion

Just ran across this


Have heard about these little gadgets but never used one so I took a chance and grabbed it, assuming the long end hooks on the prop and the other dial end hooks on the winder, I get what it does but don't really know how to use it
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Sep 13, 2019, 03:47 PM
Registered User
It appears to be winding torque meter. It tells you when to stop winding a particular motor when it has been wound to a specific amount of stored power. This is different than simply counting the number of winds. The meter is a reliable way to consistently wind to a specific power setting. Counting is just an educated guess. Meter can save on number and frequency of blown motors. In the throes of competition, one can forget a critical count, but the meter will tell you where you are at any given time, in the process.
Sep 13, 2019, 04:44 PM
BOYCOTT SCAMAZON
lectroglide's Avatar
Thread OP
ok great, am guessing you figure out torque readings on a test stand using a blast tube and the same motor your using in the model, hopefully that correct
Last edited by lectroglide; Sep 13, 2019 at 05:00 PM.
Sep 13, 2019, 06:02 PM
Registered User
Not quite. You are not seeking the breaking strain of a given motor but the maximum power that your model can handle.

Fly the airplane on increasing torque until you feel it is fully trimmed to maximum available power that it can handle. Note increasing torque value flight by flight until trimmed; from that time any occasion that you fly that model its behavior will be consistent at that final level.

Keep a note of maximum practical torque for every model you fly. Once used to using a meter you'll not bother with a counter again.
Sep 13, 2019, 06:56 PM
ffkiwi
These have been around for decades-and some very sophisticated units now exist-the one posted is a simple 'wire' torquemeter-which are generally homemade-but there are some commercial units available...

see: https://www.bmjrmodels.com/accessories/rubber-power


There have over the years been various articles written-along with the appropriate formulae-to allow people to build their own...basically-and its almost self evident if you examine one yourself-they rely on the twisting of a piece of music wire inside a tube-the wire size and length determines the torque range of the meter-and rather esoteric parameters such as Young's modulus determine this (for steel wire)-note that the length of the 'sensing element'-the piece of wire in question-is almost always shorter than the length of the overall unit-the rubber motor connects to the tube itself at the motor end-whilst the winder connects (sometimes via a thicker extension piece) to the sensing element-which is free to rotate at the winder end within the outer tube -the other end is firmly fixed (usually by soldering or riveting) inside the outer tube .....as turns are applied and torque builds up, the torque exerts a twisting moment on the meter-and the wire sensing element twists through a number of degrees (never more than a full turn-and usually quite a bit less)-there is a pointer attached to the sensing element-on the outside obviously-and the angular deflection is read on the scale as 'torque'.

Note that this is NOT necessarily accurate in terms of 'real' measurement units such as ounce-inches' or 'foot-pounds'-unless the meter has been calibrated against a known source. what it DOES provide though is relative comparison-and for our purposes we do not NEED the true value-what we need is the knowledge that if I trim my model to fly at a torque of 'X' deflection on this meter-on full turns or slightly less-I now have an accurate measure of the motor power the model is trimmed for-and I can now consistently wind the motor (and any replacement motors) up to this figure on the meter in the certain knowledge that the model can safely handle this power.

Note also that for best utilisation-you need multiple torque meters-unless you only fly one class of model-and use only one size of motor-this is one area where the 'one size fits all approach' simply will not work-you need a range of torque capacities to cover most model types-a peanut scale model may need a range of 0-2 oz inches, a small rubber scale-Walnut or similar-perhaps 0-10oz inches, P-30 0-20, Coupes 0-50 and things like Wakefields, Mulvi and large vintage 0-120 oz inches is a typical range. The REASON you need multiple meters is that the system relies on a linear twist-twice the torque-twice the angular deflection-so it is pointless-for example-trying to use a Coupe torque meter with a Peanut-the Peanut torque is so low there would be no deflection seen on the meter-conversely-the formulas only work for a deflection of 360 degrees or less-so if you overdrive the meter past 360 you will exceed the wire's elastic limit.

The length of the unit is often determined not by the sensing element-which may only be a couple of inches long in some cases (like the 0-120 oz in unit) but by the length needed to accommodate the winding tube when withdrawing it after the motor is wound-and before the prop is connected. The attached photos show some of my own units....Coupe, Indoor Open rubber scale and Peanut, ...to put things in perspective-the coupe unit covers 0-50 oz inches, the sensing element is about 12" in length-but the overall unit length is about 15 inches-to allow for the winding tube to slip out over the torque meter barrel-and still have sufficient room to access the winding hook end to fit the hold pin when reattaching the prop assembly.

ChrisM
'ffkiwi'
Sep 14, 2019, 01:59 PM
B for Bruce
BMatthews's Avatar
If you watch videos on long joiner rods used in connection with blast tubes that slide over the motor and into the model a number of times the makers of these torque meters will make them long enough that they double as the extension rod for the blast tube. This isn't so great on models with longer fuselages but on smaller stuff it can work like a treat.

And yeah, the meter spins with the winding. So you need to stop and check the torque. But when I used such a meter back when I was flying Coupe d'Hiver models I would stretch out the motor and put in roughly half the winds at full stretch until the meter came up close to the maximum torque for that size of motor and rubber. I'd then start moving back in to the model while stopping to check that I was holding the motor at around the same torque level. I'd adjust my winding or moving in as I went to hold it near the peak torque. And when I got to where the motor's Crocket hook was right by the nose I'd be at 99% of the breaking torque... ideally....

For sport flying it would be more useful as a power gauge since for sport flying to get a long useful life from the motor we only want to hit around 80% of maximum power.

This also assumes that the meter you have is able to work through the right range of torque for your motors. If this is a meter for a style of model with very light or very heavy motors it won't be useful for what you're doing with mid size models using mid size motors.

If you want to check the graduations and calibration of the meter you can do so easily enough. Use a stick or rod that fits through the loop at the face and extends out 10 inches and hang known weights at that distance. With the weight on the cross stick you'll need to twist the meter until the stick is back to horizontal. At that point it will be reading 10 times the weight in inch-ounces. So a 4 oz weight on a 10 inch arm will show where the 40 in-oz graduation should be on the dial face.

Alternately you could rig the 10 inch arm so it presses against a round wire on a digital scale and "wind" the outer tube around to get specific readings and check the graduations.
Sep 14, 2019, 02:45 PM
BOYCOTT SCAMAZON
lectroglide's Avatar
Thread OP
looks like the brass rod is too short for my application so will stick to a blast tube for now or till I can get some "one on one hands on assistance so I can actually see whats going on
Sep 14, 2019, 03:54 PM
Power Upward
GeorgeG97322's Avatar
My name is George Gilbert (RCG as georgeg97322), I live in Albany Oregon where the Willamette Modelers Club has been located and flying both indoor and outdoor free flight sense 1961. There are a few people still flying FF in the Seattle area. Most fly outdoor, but are knowledgeable about indoor as well. If you are interested, email me at [email protected] and I can send you their contact info. The Willamette modelers club hosts three full outdoor contests each year August, Sept., and October(ish) and 5 indoor contests December thru April.
Sep 14, 2019, 04:49 PM
ffkiwi
Quote:
Originally Posted by lectroglide
looks like the brass rod is too short for my application so will stick to a blast tube for now or till I can get some "one on one hands on assistance so I can actually see whats going on
You can still use it-but you'll need to make up an extension out of wire to make up the extra length you need-plus a bit more-to manipulate the blast tube. With care (and suitable pliers to bend a small diameter coil at the winder end (ie the end you'd put on the torque meter hook)-you can get by without too much loss of accuracy...and this presumes the extension is made out of sufficiently thick wire to be essentially rigid in comparison to the torque meter wire element. You see this done quite often when people don't want to be carrying around multiple torque meter to suit similar size models with different fuselage lengths.....and as BMatthews notes above -a torque meter with a 3 foot long shaft-such as might be required for a Mulvihill or Unlimited or large vintage model fuselage length -can get a bit unwieldy....

ChrisM
'ffkiwi'


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