2812 & 2822

[Erfolg]

I am considering using a 2812 on a Galaxy Me 163b

 

It would be easier to install if the motor shaft could be reversed. On most motors this is relatively simple, remove circlip, release soc head set screw and tap through. Is it the same with the 2812? has any one done it?

 

With regard the motor, I understand that they are good for 120w on a 3s Lipo. With the proviso that I am balancing weight against power, is this a good selection for a small warbird? as the originally it was intended to be used with a 480 brushed motor.

 

Me 163b link

 

 

[Tim Mackey]

I dont think that little motor is reversible. I believe the  models suggested AUW is around 2lb so for decent performance I should aim for at least 200 watts personally.

Small fast prop is surely the order of the day for this one - so maybe an inrunner would be best?

What about this type of thing ?

On a 3s lipo and maybe a 5 x 5 prop or similar, should be fast, although would need a decent throw to get her up to flying speed.

[Erfolg]

Hi Tim

 

I certainly will consider it.

 

I have a Black mantis B2846 in my 2m Sagitta, the performance is muted, so that motor which appears to interchangabel could be test run in the Sagitta Black Mantis.

 

The one thing I do not like is the weight, I have just weighed two 480 brushed @ 113g and 138 g. I do like to save weight.

[Erfolg]

Tim

 

I have just been doing a little weight estimation.

 

Partly because my small 36" Ta 152, goes like a missile on Keda A22-15m, which is to much for it.

Using Digital scales where appropriate

 

600g all kit parts

50g adhesive

20g servos

10g Rx (futaba 2.4)

130g Lipo

32g  Esc

10g propeller hub

25g Blades

 

Total 877 + 10% =964

 

Now the motor is on top so with a 2212 @ 40g = 1000grm so that is about 2.2lb or a little with a Manta.

 

 Just weighed the Ta 152H & is 548gram, with everything @ 130w.

 

I will probably decide further on, or consider if i can start of small, then remotor if beneficial, without many changes, having incorporated the necessary features whilst building.

 

At present I am undecided

[Simon Chaddock]

Erflog

A 2812 is a good 480 equivalent although it reality it is a bit more powerful and a bit more efficient however at 2.2lbs AUW 120W (55W/lb) is only going to give a rather modest performance on a scale warbird and a flying wing at that.

As Tim suggests you really need to think 200W+ i.e. rather more than a 2812 can give. 

Edited By Simon Chaddock on 01/10/2010 01:36:38

[Erfolg]

Simon & Tim

 

I suspect you are probably right.

 

The Ta 152 is being circa 260w per kg is to much, as it is faster than many jet aircraft models. Everything on launch happens in a blink.

 

So i will probably look for circa +160w - 200W, with emphasis on power to weight.

 

Motor selection is an area where I have a lot of problems. Often there is little data available on a motor, sometimes where there is, it does not always tally with personal measurements (watts).

 

In this case I do recognise that a scale affect calls for truly vertical performance, yet power of to glide, not dissimilar to a glider. Both aspects benefit from low weight.

 

 

[gary w]

The ideal motor for that would be a 2217/6 1500kv it will give you about 200watts on 3s with a 8x4 prop the motor weight is 70g.

This would give you unlimited vertical performance

I have one stuck in the front of my 2lb P51 mustang and it shift's when you need it too.  

[Erfolg]

Gary

 

It is hard to believe, but I have one mounted on my flying wing, below

 

It certainly puts out a lot of power, at one time over 330w, almost crucifying the ESC. Before repropping with a 8*4, was using a 9*5. You can just see it in the picture.

 

Unfortunately it will not fit.

 

I think Tim is correct, it will need to be an inrunner

[Steve Hargreaves - Moderator]

I have this motor in a TN Lightning (about 27oz AUW) producing 230watts on an APC 5.5x4.5E prop at about 20,000 rpm from a 3S 2200mAH Lipo......goes well!!

 

4-Max do the same motor here (at about twice the price!!) if you'd rather not buy from HK!!!

Edited By Steve Hargreaves on 01/10/2010 17:29:58

Edited By Steve Hargreaves on 01/10/2010 17:31:45

[Erfolg]

Steve

 

The Turnigy looks very interesting. Unlike some, I do like Turnigy. so far.

 

I notice that it is also available at 2200Kv, against the 2700Kv posted. Would the lower Kv be better in that I can use a larger dia propeller?

 

Does any one have an opinion.

 

Thanks Steve!

 

Erfolg

[Steve Hargreaves - Moderator]

Well, yes the 2200kv will need a bigger prop to generate the same power but as Timbo notes above a small fast prop is what is needed for this sort of model...why would you want a bigger one??

 

FYI the TN EE Lightning is a pusher design...it was a free plan in the mag a couple of years ago if that helps you place it.

 

If I remember rightly didn't Nigel Hawes review a similar Komet to yours? One from Australia if I remember rightly......I wonder what motor he used in that??

[Erfolg]

Bigger props are more efficient that is all

 

I do realise that       P=2piNT, which suggests that if you increase the revs, the power will be greater, although it is also true that if the torque is higher then this also increases the power.

 

So at the end of the day it is a balance, of torque and revs.

 

I have always favoured large diameters, just because they are more afficient, which is the debate of another current thread for full size aircraft.

 

There is another reason in that I want to use a folding propeller, and Graupner small blades seem to finish at 5" dia.

 

I still favour one of the Turnigy's, but which one?

Edited By Erfolg on 01/10/2010 21:19:18

[Steve Hargreaves - Moderator]

This is true Erfolg but what you want (I assume) is a small model that is going to rip around the sky a bit & IMHO the best way to achieve this is with a small prop spinning very fast...yes the 7x5 (or whatever) you fit to the 2200kv motor might be more efficient but in reality who cares as long as it does the job......lets be silly & fit a 1000kv motor & a 9x6 prop....I'm sure that would be more efficient still but isn't really what we're looking for....

 

Another thought.....the ME163 is rocket propelled isn't it? It didn't have a prop at the back so a small one is easier to ignore 

 

All that said I don't have any experience with the 2200kv version so maybe I should shut up but I do know that you won't be disappointed with the thrust from the 2700kv motor on a 5.5x4.5 APC  

[Steve Hargreaves - Moderator]

PS...I dug out the review by Nigel Hawes of the EPP Komet  from Austalia (Feb 2007   pages 58-60 if you're interested!!!) as this seems a pretty similar model the one you're looking at...he used a Mega 16/15/3 in one & a JP EnErG 2815/1400 in the other but doesn't say which prop he used.....Nige got 250watts for an AUW of 24oz.....

 

I can't find the EnErG motor but would guess at it have a kv value of 1400 (all the 2815s on the Perkins website seem to have much higher kvs) so you'd need a pretty big prop on that...8x4 or something...

 

The Mega is a 3000kv motor according to Puffin & can be used in EDF so a pretty small prop on this one a 4.7 x 4.2 according to Mr Emms

 

HTH...

[Erfolg]

After a lot of deliberation, I came to a conclusion.

 

I have purchased the following HXT 2835 s. The one with the heat sink. I have studied the kit, and the motor seems to fit easily into the space, available. An unexpected benefit is that it is cheaper than the non heatsink version. It is also slightly lighter.

 

I have decided on a heat sink +ducting from recent experience. I Was testing a repaired crashed model, whilst doing a long motor run and stick waggling, the reason is boring and a sad tale. When I realised that the motor was overheating. I have now provided ventilation to this motor.

 

So it seems prudent to start from the begin with the intention of managing heat.

 

[Steve Hargreaves - Moderator]

Should go well Erfolg....

 

Certainly cooling on a pusher motor can be an issue as it doesn't have the full prop blast that it would get if it were in a tractor position....I've not found a problem on my Lightning as the motor is fully exposed......!!

[Erfolg]

Steve

 

The kit is arranged for a tractor propeller.

 

The back is quite refined, leaving no room for a motor of any size.

 

I have a 36" Dornier 335, which uses two 2812 motors. This model is very fast on its full throttle 220 w. Yet looks most impressive at slower speeds. On this basis yourself and Timbo are right to recommend a more powerful motor.

 

I am only concerned with cooling now, since realising that even a full power climb out of a glider lasts for less than 30s, so little heat is generated. Yet even a sports plane on half throttle generates a lot of heat after 6-7 minutes.

 

Maybe the 163 is more akin to a glider, we will see.

Edited By Erfolg on 06/10/2010 10:31:09

[Steve Hargreaves - Moderator]

Ah, my mistake....I assumed the Me163 would use a pusher arrangement!!!

 

If my memory serves me the Me163 was designed for a rocket motor to get it up to speed/height quickly to shoot down the Allied bombers (it would get to 39,000ft in about 3 minutes!!!)......after the rocket motor cut it glided back to its airfield....it was by all accounts a superb glider & the problem was in getting it onto the ground again

[Tim Mackey]

I suspect that the main parameter for your cooling issue may be the design and quality of the motor itself. Most of my inrunners get pretty darn hot - yet I have only ever cooked one to failure - a really cheapo job of dubious origin. Good quality motors will have properly bound wiring, solid magnet fixings and case material made of something better than chinese monkey metal.

Shouldnt be too hard to arrange few cooling slots around the area?

[Erfolg]

Ohhh Timbo!

 

How could you upset me so? Yes, I am the one who managed to cook his Tornado Inrunner.

 

In respect to the Me 163,  it is relatively easy to arrange an internal cooling duct, out through the faux rocket tailpipe. Most of the inrunners I have, have a series of cooling holes arranged on the front cover. Does any one have any indication if this will be sufficient to cool the motor, given that there will be a full width spinner?

 

Point of interest, the burnt out Tornado had no such cooling, partly out of necessity that an epicyclic gearbox was screwed onto the front end. 

 

Weather looks good and batteries are on charge.