Brushed 400 replacement with brushless

[CW]

I would like to replace the brushed400 running on 2s lipos & 6x3 folder in a 620 grm 1.5mtr  glider. I'm not looking for exceptional performance just an improvement over the rather poor 400.

Ideally a straight swap mounting wise would be useful which may mean an inrunner but could  possibly modify the nose to take an outrunner. I would like to use the 7.4 lipos if possible.

Suggestions on motor/ folding prop combos particularly from Hobby City or other reasonable cost suppliers welcome. Thanks

[Tim Mackey]

http://www.brchobbies.co.uk/?page=shop&item=233

 

You may want to use a slightly larger prop ( maybe up to 10" ) on a 2s Lipo, but for glider, i reckon that is a good thing anyway - more thrust, less pitch speed.

[CW]

Thanks Timbo, that looks a very reasonable solution. Just for interest; what's your take on the inrunner option ?

[Tim Mackey]

Most inrunners tend to be a bit high Kv for your needs IMO - easier to fit maybe yes, but then modelling is so often about adapting and changing things to suit. Inrunners also tend to be more expensive, and you did stae you wanted low budget stuff

[hotspur]

I want to convert too.

What would do for a power train for a 400 can motor 1.5m glider ?  (ie Cherub). Lipo; Sc, outrunner motor, props, etc.

 

Similarly,  for a 600 can motor  glider,  just to get a decent launch, rather than swooping earthwards, with a load of NiCd up front.

 

As I have only ever used Ni batteries and SCs, I suppose I am letting myself in for new chargers, balancers, motors , SCs  etc.

Where is a decent source for this kit ?

 

 

[Tim Mackey]

Well the link above should do you for the 1.5metre jobby - if you want more oomph, just use a 3s lipo instead of a 2s. What weight is the 600 brushed job? Stick to an outrunner, with low to medium Kv so that you can swing a biggish prop ( more thrust and less speed ) and get a wattmeter to ensure you stay within component limits.

Decent source ( info and materials ) ?

BRC hobbies

GiantCod

Flying Wings.co.uk

Puffin Models

and so on...there are loads around these days.

[Erfolg]

In general I think I agree with Timbo.

 

I personally have one thing to add. Go for a low Kv motor, why because you want to swing the biggest propeller possible, without drawing a high current. As a principal a bigger dia.propeller is generally more efficient.

 

Ohh one other thing, if you swing a large diameter propeller with a brushless, the stresses at the hub will be a lot higher than are possible with a brushed motor. Make sure the propeller is a Graupner or Aeronauht carbon. As some of the non branded props, do not take the stresses. Some do, as used by Multiplex models, but many do not. You may wonder how I can be so adamant. I have had a number of failures and witnessed others, the motor is torn completely out, if lucky hanging by the wires.

 

Going brushless is the right thing to do, by far. It turns the equivalent of a Reliant Robin into Porsche. That is controllable fluid power.

 

Erfolg 

[Tim Mackey]

Beware going too low in Kv rating of your motor - when you are only using a low cell count battery like a 2s or 3s the revs will be proprtionally lower, and you may end up simply revving too low to produce the thrust you desire...and of course overall power will also be lower with a low Kv motor. The principle is sound, but just be aware that in order to get decent power outputs from low Kv motors, you generally need very large diameter props and certain models will of course prohibit this.

 

[CW]

Posted by Timbo - Moderator on 16/08/2009 11:04:26:

http://www.brchobbies.co.uk/?page=shop&item=233

 

You may want to use a slightly larger prop ( maybe up to 10" ) on a 2s Lipo, but for glider, i reckon that is a good thing anyway - more thrust, less pitch speed.

 

 Timbo, have ordered the suggested motor from BRC thanks.

Regarding props : you suggest up to 10" dia : what sort of pitch do you recommend for this (assume it's a folder) ? Thanks

[Erfolg]

I have no proof, yet I suspect that the improvement in propeller efficinecy will more than offset the drop in power.

Given that P =2(Pi)nt the whole relationship is quite linear, where as propeller efficiency has a ^2 some where in it. Sometimes, I think I should rush for some text books. Then i think why bother, does it really matter?

 

What may be a useful comparison, is I vaguely remember, the Wakefields argument. Was it better to have a small toothpick propeller, revving. Or a large diameter propeller turning slowly. We now know with that particular debate the large diameter won.

 

Of course, the issue was about getting a model as high as possible, on limited power. For a glider the comparison may be valid. However if speed is the name of the game, I certainly do not know.

 

Yet power duration is just about revs, lots of them. So may be there is more to the argument, where time is limited.

 

I do suspect though there is a trade of between revs and prop dia. The question is who knows or can be bothered to think of the answer. Maybe these electro slot type models, I guess with this 200m cut of device, overall efficiency will not be a concern, as on the 30s rule.

 

Erfolg

[Tim Mackey]

Posted by CW on 17/08/2009 16:04:59:

Posted by Timbo - Moderator on 16/08/2009 11:04:26:

http://www.brchobbies.co.uk/?page=shop&item=233

 

You may want to use a slightly larger prop ( maybe up to 10" ) on a 2s Lipo, but for glider, i reckon that is a good thing anyway - more thrust, less pitch speed.

 

 Timbo, have ordered the suggested motor from BRC thanks.

Regarding props : you suggest up to 10" dia : what sort of pitch do you recommend for this (assume it's a folder) ? Thanks

 Not sure it would be available as a folder in 10" diameter ( but may well be ) but perhaps around 5" pitch or so.

If you struggle to find one, then a 9 X6 may be useable, and these are certainly available as folders.

[IanN]

What about the emax 2812 - the one Nigel Hawes used for both Flingwing and the more recent Hepcat reviews?

 

Would that be a good choice for this type of model?

[Tim Mackey]

Not IMO as its too high a Kv at 1500+ which makes it suitable for smaller faster propellors and models.

[Erfolg]

There is a version, which is a lower Kv, using the same frame,armature. I have one, which I used on aTomboy. Works well for its size and price. I use it with a 3s.

 

The main reservation I have is its largish diameter, on a typical slim nosed glider.

 

I am away from home so can not get the model out or data sheet.

 

Erfolg

[Tim Mackey]

duhhhh, this is the one I have already linked to erfolg

[Erfolg]

If it is the 2822, I apolgise. In mittigation I did not have access to my file.

[hotspur]

Thanks for all that. I will go to BRC for motor/sc. deal.

 

What about charging Lipo batts. ? Is a built-in balancer needed ?

Or can I start off with a simple one ?

[hotspur]

Oh, what motor etc for a 600 glider of just over 1 kg.

[Tim Mackey]

I would not recommend a non balancer charger - the price difference is marginal, but the lifespan of your batteries will be greatly increased.

 

Tell you what hotspur... I have given some clues, there are LOADS of relevant threads on here, so why not try to figure the 600 glider out yourself. Look at BRC, Puffin, Giant Cod etc, and see if you can find the motor that would do the job....

Then, post back here with your findings, and we can say yeh /nay before you spend your money 

[Erfolg]

Hotspur

 

Electrics, in this present era, using contemporary equipment, are not a "Black Art".

 

Budget charger/balancers, budget outrunner motors, and cheap Lipos such as Loong Max, Zippy,  Flightmax are all perfectly serviceable. The same goes for most other bits.

 

If you buy a Shultze charger, yep, you will have a quality product, also if you buy an Axi, Hacker motor, it will be amongst the very best, the same goes for all the other components. Yet unless you intended entering competitions, or must have the equivalent a Bentley or Maybach, the Ford Mondeo that these other products often represent, will suffice. To the extent, if your selection is not quite to your liking, you will be able to afford to remedy the situation.

[Boots]

I purchased an EMAX 2812 outrunner to replace a graupner speed 400 so I took a short length of 25mm round wooden dowel (broom handle) and screwed the radial mount to that. The advantage to this is no mod to original motor mount, can swap back to speed 400 at any time

[Romeo Whisky]

Just a thought - a 400 can motor has a Kv of around 2200.

 

You can indeed get inrunners at this Kv and they're a lot easier to fit to a model designed for a 400 than trying to put an outrunner in there.

 

For my Mini-Mag I put in a Tornado BM400 1800Kv and it has proved a great upgrade which I've used for years.  Overlander don't do these any more, but I've seen them advertised more recently by Gliders (UK) in RCME, and several sources (eg. Giant Cod) do 2200Kv inrunners.  You can also get 2700Kv inrunners (equivalent of 480 motor) which might be even better on 7.4V.

 

Hotspur - you can also get 600BM inrunners at anything from 850Kv to 1500Kv.  

 

I inrunners - they're so smooth-running too.

[Tim Mackey]

Indeed, but then I feel many people are missing out on the benefit of using an outrunner ( even in a model "designed" around a 400 can) and that is - the ability to swing a larger prop. This results in much greater effiicency, leading to longer flights, less noise, and lets not forget that most models designed for speed 400s etc were only designed that particular way because there were simply not any other electric motors around in those days!

Finally, most Inrunners tend to be more expensive than outrunners, and outrunners come in more flavours - they are not restricted to just low Kvs - if wound correctly they perform admirably as high revving fan drivers etc.

Not withstanding all that, I accept that mounting them can be a little more difficult in some models.

[Erfolg]

Timbo

 

I certainly agree, with all your comments.

 

I have a Tornado 3618 inrunner, I do agree that it rectro fits well into older models, in this case a 3m Algebra. Yet it came at a cost, if I rember +£60. I have seen Overlander Thumpers, which beay iy hands down for Watts/£. Although not so well suited to the miniscule open class glider noses of yore,

 

Erfolg 

 

 

[CW]

Posted by Timbo - Moderator on 16/08/2009 11:04:26:

http://www.brchobbies.co.uk/?page=shop&item=233

 

You may want to use a slightly larger prop ( maybe up to 10" ) on a 2s Lipo, but for glider, i reckon that is a good thing anyway - more thrust, less pitch speed.

 As a follow up to the original query I can report the following which may be of use to others : I replaced the speed 400 with the above motor/esc combo as recommended by Timbo . I ended up with using a 3s 2200 Zippy lipo and 8x4 folding prop with ali spinner (3mm shaft size) from Hobby City.  The performance of the model (Cherub) was completely transformed : there is more than enough power for rapid climb and half throttle sees it cruising around for 25minutes plus. I highly recommend this combo.