OS electric motors

[Dave Hopkin]

Is there a database/public spreadsheet somewhere where we can add actual Electric Motor Performance data from bench tests under set conditions?, I would find that useful I know and I think a lot of others would too

Its one thing to work out what motor you need, another thing to claw through the claims manufacturers put out and quite often they give you only part of the data.....

[Biggles' Elder Brother - Moderator]

The simple answer Dave is "yes" thanks to Steve Hargreaves. You can find it here. But I don't know how current it is - if you'll excuse the pun!

BEB

[Dave Hopkin]

Posted by Biggles' Elder Brother - Moderator on 02/11/2014 18:22:44:

The simple answer Dave is "yes" thanks to Steve Hargreaves. You can find it here. But I don't know how current it is - if you'll excuse the pun!

BEB

Its a pity it doesn't allow searching by motor characteristics.... a bit like motorcalc does

[GrahamWh]

From what I read somewhere that I can not remember, I think the OS data uses a lab power source rather than an actual lipo, hence the voltage given as 12.6 volts on their tables, which would be a fully charged 3s lipo with no voltage drop. Official OS data here:

**LINK**

[Biggles' Elder Brother - Moderator]

Feel free to update it!

BEB

[Frank Skilbeck]

Posted by Biggles' Elder Brother - Moderator on 02/11/2014 17:48:27:

Well - I can't say I've tested all combinations Phillip - but I used the 5020-490 in a recent conversion.

OS predicted:

47A and 1.18kW with a 14x7 prop.

I actually got:

56A and 1.28kW (that's static on the ground)

So the current was a bit adrift but the power was pretty spot on. So I would hesitate to describe their figures as "fiction"!

BEB

And part of that could be down to different props, I've found different manufacturers props of the same size can have quite a difference on the power.

[Peter Beeney]

I’m sure you’re absolutely right there, Frank, but I try to find the best prop by a bit of trial and error. I’ve also noticed particularly that props of the same size but by different manufacturers can give substantially different outcomes, too. One way of checking might be a static thrust check, but I use an ammeter and a tacho; plus a handful of props and some flying tests.

Fitting a bigger prop on, either by pitch, diameter or both is always going to make the motor run slower, thus increasing the power required, but it doesn’t necessarily always make the model fly any better. I would consider that relating to electrical powered models it’s not entirely necessary to try and realise the largest amount power, it terms of watts from the battery, that gives the best result.

PB

[Philip Craig]

Posted by Biggles' Elder Brother - Moderator on 02/11/2014 17:48:27:

Well - I can't say I've tested all combinations Phillip - but I used the 5020-490 in a recent conversion.

OS predicted:

47A and 1.18kW with a 14x7 prop.

I actually got:

56A and 1.28kW (that's static on the ground)

So the current was a bit adrift but the power was pretty spot on. So I would hesitate to describe their figures as "fiction"!

BEB

Thanks. Using the data given by OS and comparing with what you got, you are right, they are pretty much spot on. Using the points and calculating the current at 1280w, you get 52A. Compared to the 56A you tested, it is pretty much the same result.

I have a 5020-490 in an aircraft and I'm really happy with it but I have no idea how it compares to anything. I am considering putting a 5025-375 into a larger aircraft and am a bit nervous. If the numbers published are spot on as they seem to be, then I have nothing to worry about.