E props

[Fly Boy 3]

Hi all, after 35 years of ic flying I am slowly getting into electrics. Wondered if I really need E props as I have literally dozens of ic props.  Are all my ic props redundant ?  Cheers

[Dickw]

No, IC props are fine on electrics and I often use them as they don't break so easily. They are probably just a bit less efficient.

You can't use e props on IC though.

 

Dick

[Tom Gaskin 1]

Use them if you have the right size. E props are lighter as they don't have to put up with the power pulses of IC, certainly I use what I have in stock, whether IC or E.

 

 

Tom

[Geoff S]

The only problem with using IC props on an electric motor is that the hole size is sometimes too big, otherwise they're fine.

[Chris Walby]

5 hours ago, Dickw said:

No, IC props are fine on electrics and I often use them as they don't break so easily. They are probably just a bit less efficient.

You can't use e props on IC though.

 

Dick

Not sure why IC props are less efficient, but would say if its a hand launch or nose over with power on then more likely to bend the motor shaft if using an IC prop.

 

[Dickw]

3 hours ago, Chris Walby said:

Not sure why IC props are less efficient, but would say if its a hand launch or nose over with power on then more likely to bend the motor shaft if using an IC prop.

 

IC props usually have thicker blades and are heavier to cope with the power pulses of the IC motor. E props don’t have that problem so are made thinner and lighter for a reason.

You can bend a shaft with an e prop (done it!) which is why prop savers were invented, but I only use IC props on suitable motors so have never bent a shaft with one.

 

Dick

[Fly Boy 3]

Thanks all, apologies wrong thread. agree with Geoff regarding hole diams in props. Can you tell me if washers are available to adapt the diameters, an where can I 

purchase them. . Thanks

[SIMON CRAGG]

I personally would never use an IC prop on an electric motor, and sold all mine as a job lot many years ago.

 

They are heavier and the mounting boss is much wider.

 

I had one (balanced), vibrate so badly, it ripped the mount and cowl out of the model and destroyed the front.

 

I did several experiments, and found the e props much better all round, confirmed by the watt meter.

 

As an aside, I always use metal backed spinners, as the normal plastic items can also cause bad vibration even on an e prop!.

 

 

[EvilC57]

2 hours ago, Fly Boy 3 said:

Thanks all, apologies wrong thread. agree with Geoff regarding hole diams in props. Can you tell me if washers are available to adapt the diameters, an where can I 

purchase them. . Thanks

When you buy APC propellers they come with a a number of adapters of different sizes in the packet.

[leccyflyer]

One of my adages is never say never. Despite having dozens and dozens of e props in a vast range of sizes I've still found some of my IC props to be very usable and efficient props for electric. One example would be my lovely wee Robbe Dynamic 7" x 4" props which are still in use on a couple of sports models giving exactly the 25amp current draw that I was looking for. Still in use more than 20 years later and tough as old boots. Similarly the JP bendy props that I have on my BC Bearcat stands up to the rigours of belly landing with little protection on dodgy fields much better than brittle APC-E props of equivalent size and pulls the Bearcat around with aplomb. Finally my venerable Top Flite 12" x 6" wooden props do a grand job on my Magnatilla and look the part into the bargain. I still keep a collection of such wooden props, which are used when they suit.

[PatMc]

2 hours ago, SIMON CRAGG said:

...I did several experiments, and found the e props much better all round, confirmed by the watt meter.

 

 

The wattmeter only measures the power input. I fail to see how it could confirm the difference in performance or efficiency of diferent props.

[leccyflyer]

Good point Pat - I was describing this in a discussion about using the WattsMeter  at the field a couple of weeks ago. Many years ago I was running a series of motor tests from my Balsacraft Hurricane - brushed sp600 sized motors at the time - and the results were interesting. If taken at face value one motor and prop combination would have really stood out above the others as indicating it would produce the most power, given that it was pulling the most amps and generating the most watts. That was entirely misleading since the highly inefficient grotty old sp600 motor was just an amp hog, without producing any more waft compared to the other equivalent motors, with much lower prop RPM. The light show of sparks at the brushes and smell of burning were other pointers to how well the motor wasn't doing.  My notes at the time were two words - Bin It!

[Andy Stephenson]

1 hour ago, EvilC57 said:

When you buy APC propellers they come with a a number of adapters of different sizes in the packet.

Only APCE props come with spacers, you don't get them with IC props.

Providing you can get a prop to centre correctly using a piece of fuel tube or tape as a spacer, if you tighten the nut sufficiently it will stay centred.   

[RottenRow]

40 minutes ago, PatMc said:

The wattmeter only measures the power input. I fail to see how it could confirm the difference in performance or efficiency of diferent props.

Exactly. Put a lump of 2”x1” on the motor. It’ll pull plenty of amps. The model won’t fly very well though.

 

Brian.

[GaryW]

23 minutes ago, Andy Stephenson said:

Only APCE props come with spacers, you don't get them with IC props.

Providing you can get a prop to centre correctly using a piece of fuel tube or tape as a spacer, if you tighten the nut sufficiently it will stay centred.   

 

Actually Master Airscrew Electric Props come with spacers as well

[GrumpyGnome]

Several brands come with spacers................ I think the point was that not all APC props come with spacers, only the electric ones.

[Cuban8]

I think you've just got to suck it and see.....I'm sure someone far more cleverer than myself could produce a thesis based on fluid dynamics, aerodynamics, Reynolds Numbers etc etc and come up with a definitive answer. Personally, I've never tried an IC prop on any of my electrics, but I'm sure it'd work just fine particularly in smaller sizes (say below 10" diameter) where the smaller mass compared to larger IC props will have a reduced effect on loading an electric motor during quick acceleration. Whether it's significant or relevant I really couldn't say.

Edited March 13 by Cuban8

[SIMON CRAGG]

Whatt meter = my bad!

[EvilC57]

57 minutes ago, GrumpyGnome said:

Several brands come with spacers................ I think the point was that not all APC props come with spacers, only the electric ones.

I must admit when I wrote my original reply to FB3 I couldn't remember whether APC glow props come with spacers, as it's several years since I've bought any. I know their E props come with spacers though, as I've bought them more recently.

[Martin Harris - Moderator]

6 hours ago, SIMON CRAGG said:

Whatt meter = my bad!

What?  What's a whatt? What's bad in your earlier post?  The unit being measured is the watt (note the lack of capitalisation) abbreviated to W (note the capitalisation).

 

Unless you're referring to a trade name, I think you could argue that wattmeter without the space would be the correct spelling for the power measuring equivalent of the voltage measuring voltmeter.  An ammeter rather messes up the pattern...

[leccyflyer]

The original wattmeter, before any of the knock-offs were a glint in their daddy's diodes was the Astro Flight 101 Super Whattmeter.

 

[PeterF]

One model I use an APC IC prop on is my Ripmax Rapier which runs a 9x7 at >16,000rpm in a full power dive as the motor unloads. This is on the APC limit for E props (150,000/9 = 16,700rpm) but IC at this diameter is good to higher rpm (190,000/9 = 21,100rpm).

 

In terms of relative performance of IC and E props, APC publish information on each prop for thrust and power at APC Performance Data.

 

 

[Geoff S]

15 hours ago, leccyflyer said:

The original wattmeter, before any of the knock-offs were a glint in their daddy's diodes was the Astro Flight 101 Super Whattmeter.

 

 

They cost a fortune as well!  I've had mine for years (at least 10) and, IIRC, cost £50.  No LiPo checking facility either.  I use mine as a standard to check the cheaper alternatives.  I don't know why they're called Wattmeters because the main purpose is to measure current, I find.  OK, they measure voltage as well, so power consumption (watts) follows.  Nevertheless, an indispensable piece of kit for any who use electrical propulsion.

 

PS Just had a look at mine, and you're right, they are called Whattmeters, with an added, and unnecessary, 'h'.

Edited March 14 by Geoff S

[leccyflyer]

22 minutes ago, Geoff S said:

 

They cost a fortune as well!  I've had mine for years (at least 10) and, IIRC, cost £50.  No LiPo checking facility either.  I use mine as a standard to check the cheaper alternatives.  I don't know why they're called Wattmeters because the main purpose is to measure current, I find.  OK, they measure voltage as well, so power consumption (watts) follows.  Nevertheless, an indispensable piece of kit for any who use electrical propulsion.

 

PS Just had a look at mine, and you're right, they are called Whattmeters, with an added, and unnecessary, 'h'.

They are called Wattmeters presumably because they measure the watts, at least mine does?

 

No additional calculation required. The readout gives watts, amps, voltage and aH consumed. Together with an optical tachometer that was the standard kit for the measurements you needed to work with your power train, before Lipos were ever even a thing. Later on I added a Graupner clamp meter, just for convenience sake as being much more rapid in use at the field, without having to make any additional connections. The Whattmeter remains a quality piece of kit.

 

[Simon Chaddock]

Remember if you refer to a Wattmeter it is the trade name not the correct technical description. A company can call its product what it likes. Hoover, vacuum cleaner, Biro and ballpoint pen come to mind.