Ripmax Wot 4 ARTF on Electric

[Mitchell Howard]

Apologies if this is a topic done to death. Following on from previous threads (**LINK**), I've laid my hands on a Wot 4 ARTF balsa and need to buy the power system.

 

1. Ripmax say ESC 60A, LiPo 4S1P 4500mAh, Motor QuantumII 40 800KV but no prop suggestion.
2. Ripmax also say .40 2-Stroke Equivalent Setup, 4S 4500mAh, 60A ESC, 12x9W" Prop.
3. 4-max say PO-5055-595 (595KV, 58A max 10s), 4S 4500mAh, 60A ESC, Prop APCE 13x8.
   1. Edit - I've just noticed this motor is what 4max consider their equivalent to the QuantumII 55, also suggesting it needs a 70A ESC and 14x7 prop on 4S.
4. Chris Foss site says very little other than .30 for docile 'advanced trainer' and .60 for a vertical climbing animal.

 

I've already got some 3700mAh 4S (Zeee) and 5000mAh 4S packs (Radient) that I'd like to re-use, preferably the Zeee ones as they're rather affordable. I'm sure I've got a 12x8 prop somewhere too. I've also got a ZTW Beatles 80A ESC unopened.

 

Can anyone provide any useful recommendations before I commit?

Edited May 22, 2021 by Mitchell Howard

[dan h]

Hi Mitchell

 

I have recently setup one of these I tried it with an overlander thumper 4250 800kv on 4s with several props which it flew ok but wasn't enough power for me.

 

So then I fitted a turnigy 4248 650kv on a 5cell. Erm that's more like it !!!! Unlimited vertical etc. Lots more fun !!!!

 

I cannot comment on any of the setups you have written down. 

I would say imo if you want trainer like flying then 4 cells is enough..but if you want lots of power then 5 cells is the way to go..

Remember the auw is around 6lb.

 

Hope this may help

 

Dan

 

 

[Ron Gray]

I fitted mine out with the motor from an ‘expired’ FMS Olympus, a 4258 Kv550 swinging a 15x8 prop. Similar to Dan, on 4s it’s fairly sedate but on 5s it’s good fun, on 6s totally bonkers.

 

Edited May 22, 2021 by Ron Gray

[SIMON CRAGG]

4250-800 on 5 or 6 cells should do the job!

 

Have a play with props on e.calc, very useful bit of kit.

[i12fly]

I have a Wot 4, mk2 (I think), converted myself to electric and operating with Grand Turbo GT3526-04 with H/King 70A blue series, 12x6E APC and 4s 4000-5000 battery. It gives 825W maximum and weighs 5lb5oz so 156W/lb, 21.4 oz/ft2. Pretty well unlimited vertical, a very good performer and good in wind. I fitted the battery through a hatch in the top front so it turned out a bit nose heavy and needing a couple of ounces weight in the tail. Bought a carbon u/c and reinforced the mounting before flying.

I like it! Don't know if this helps

Edit: the motor was 870KV

Edited May 22, 2021 by i12fly

[Mitchell Howard]

1 minute ago, i12fly said:

I have a Wot 4, mk2 (I think), converted myself to electric and operating with Grand Turbo GT3526-04 with H/King 70A blue series, 12x6E APC and 4s 4000-5000 battery. It gives 825W maximum and weighs 5lb5oz so 156W/lb, 21.4 oz/ft2. Pretty well unlimited vertical, a very good performer and good in wind. I fitted the battery through a hatch in the top front so it turned out a bit nose heavy and needing a couple of ounces weight in the tail. Bought a carbon u/c and reinforced the mounting before flying.

I like it! Don't know if this helps

 

That seems like a really nice balance - I feel like the move to 5S is often premature, given amp draw being somewhere around 30-40A on 4S - the C ratings of the lipos and ESCs aren't being exploited enough by bigger props and motors.

 

What flight times do you get on that setup?

[dan h]

1 hour ago, Ron Gray said:

I fitted mine out with the motor from an ‘expired’ FMS Olympus, a 4258 Kv550 swinging a 15x8 prop. Similar to Dan, on 4s it’s fairly sedate but on 5s it’s good fun, on 6s totally bonkers.

 

 

 

Ron..6 cells do you remove the wing to fit the Lipo. 5s is quite a tight squeeze.

 

Mitchell I see you are fairly new to flying? My 5 cell setup I get about 7mins with alot of full throttle.

[Ron Gray]

52 minutes ago, dan h said:

Ron..6 cells do you remove the wing to fit the Lipo. 5s is quite a tight squeeze.

No, I feed the packs in through the battery hatch, but don’t expect to get a 6s 5000mAh pack in there! Mine tend to be around the 3000mAh size.

[Mitchell Howard]

1 hour ago, dan h said:

 

 

Ron..6 cells do you remove the wing to fit the Lipo. 5s is quite a tight squeeze.

 

Mitchell I see you are fairly new to flying? My 5 cell setup I get about 7mins with alot of full throttle.

 

Hi Dan, yes, very new! I have an A test booked for tomorrow (weather doesn't look great) so really looking forward to getting some independence at the field.

 

I've got a technical background, so the electrics hasn't fazed me too much, although a lot of the 'in-practice' vs theory lessons are still being learnt! Is it not correct to say I can shift more air with a bigger prop (thereby negating the lower RPM of 4S), fit a bigger motor to deal with the amp draw of the bigger prop, run a bigger ESC, say 80A, then give it 4S to better exploit the amps it can deliver - my packs are 60C 3700mAh - they should be able to deliver 222A - what am I missing, why do people move to 5S?

Edited May 22, 2021 by Mitchell Howard
Clarity

[Mitchell Howard]

2 hours ago, Mitchell Howard said:

 

That seems like a really nice balance - I feel like the move to 5S is often premature, given amp draw being somewhere around 30-40A on 4S - the C ratings of the lipos and ESCs aren't being exploited enough by bigger props and motors.

 

What flight times do you get on that setup?

 

4 hours ago, dan h said:

Hi Mitchell

 

I have recently setup one of these I tried it with an overlander thumper 4250 800kv on 4s with several props which it flew ok but wasn't enough power for me.

 

So then I fitted a turnigy 4248 650kv on a 5cell. Erm that's more like it !!!! Unlimited vertical etc. Lots more fun !!!!

 

I cannot comment on any of the setups you have written down. 

I would say imo if you want trainer like flying then 4 cells is enough..but if you want lots of power then 5 cells is the way to go..

Remember the auw is around 6lb.

 

Hope this may help

 

Dan

 

 

 

I don't think I've ever weighed my trainer, but I figured it would be heavier than the Wot4. I think my bigger picture is being distorted by learning on a powerful trainer - Seagull Boomerang, 12*8 prop, quantumii 40, 60A ESC, 3700 4S 60C. At the time I bought the trainer I really didn't have a clue. Would be clever I think to get it on the scales and buy a wattmeter.

[Bob Cotsford]

1 hour ago, Mitchell Howard said:

what am I missing, why do people move to 5S?

While prop size can be a limiting factor on low cell count/large prop setups, current draw is usually a prime consideration.  Apart from power loss/heat generation being proportional to the square of the current there's the simple matter of economics - lower current ESCs are cheaper not to mention smaller.  Connectors don't need to be rated as highly, wires can be lighter gauge - I can't see where a lower current isn't a benefit. 

Edited May 22, 2021 by Bob Cotsford

[Dad_flyer]

1 hour ago, Mitchell Howard said:

Is it not correct to say I can shift more air with a bigger prop (thereby negating the lower RPM of 4S), fit a bigger motor to deal with the amp draw of the bigger prop, run a bigger ESC, say 80A, then give it 4S to better exploit the amps it can deliver - my packs are 60C 3700mAh - they should be able to deliver 222A - what am I missing, why do people move to 5S?

There are a number of other variables, but most of them come out in the wash. 

For example: Take a given prop and required rpm, that gives the actual power for the model. On 4s it has a lower voltage, so will draw more current. High current tends to fry things, so you want a high current ESC. Ok, go for 6s. Lower current is good, so smaller ESC, except that 24V takes the next level of capacitor etc and again tends to mean a bigger or more expensive ESC to be rated for 6s.

 

Lower current stresses the battery less, except that for a certain flight time you want a higher capacity battery at 4s and a lower capacity at 6s and the C of the required current comes out the same. The battery internal resistance also comes out in the wash for the same reason. Lower resistance, but higher current at 4s, low current but higher resistance for the lower mAh 6s.

 

Lower current is good for the motor too (except again many are only rated to 3s or 4s, though there is nothing really voltage dependent there). However to turn at the same RPM with more cells you need a lower KV motor. Lower KV has more turns of wire, so a higher internal resistance, which wastes more power. For a given size and weight of motor the longer wire also needs to be thinner, so even more resistance. Going for a smaller prop on 6s allows you to keep the higher KV motor, but small props are less efficient at moving air. If that smaller prop is ok, the 4s could drive it with an even more efficient even higher KV motor.

 

I think the only actual difference, if you start off from a certain prop, is in the connectors and wire between the motor and battery. There the 6s definitely wins. 

 

That does assume that the actual ESC, motor with the right KV and current capacity, and battery size are available. In practice one is often starting from a small number of available motors, and we have some batteries. Or we already have a model with motor and ESC installed, but there is not quite enough power. Also this only holds in the 'mid' range of current and battery, which is around this size. ESC, wires and connectors over 60 or 80A are pushing it. But in looking at systems around 600-900W I think it is a matter of taste.

[i12fly]

14 hours ago, Mitchell Howard said:

 

That seems like a really nice balance - I feel like the move to 5S is often premature, given amp draw being somewhere around 30-40A on 4S - the C ratings of the lipos and ESCs aren't being exploited enough by bigger props and motors.

 

What flight times do you get on that setup?

7 to 8minutes depends on how much throttle I use. I don't use full throttle much because it isn't necessary for ordinary aerobatics. On landing I have 20-25% left and battery and esc are only slightly warm

[Trevor Crook]

Mitchell, I would buy an 800kV -ish motor capable of coping with around 80A and use the rest of the kit you already have, I think you will be in the right ballpark. You will need a wattmeter though if you don't have one already.

Start with your 12 x 8 prop and measure power and current. If you have at least 100W per pound of model weight, it should fly OK, but make sure the current is well under 80A. You can try different props to get different power outputs. I normally set my flight timer to 5 minutes initially, then adjust accordingly after I measure how much is left in the pack.

Have fun and mind your fingers!

[Geoff S]

I have a Foxy 4020/10 (kv=750 rpm/v) in my Wot 4 ARTF.   It draws about 45 amps from a 4S 4AH LiPo with a 12x6 prop and provides me with adequate performance for up 10 minutes.

 

 

 

 

Geoff

 

 

 

[Mitchell Howard]

Thought you'd be interested to know what I've found on my first wattmeter run. I haven't weighed the trainer yet.

 

[Wilco Wingco]

SS40 Perfect ?