T-Rex 450 3S motor super test

Written by Ashley Davis Friday, 28 April 2006 00:00

Introduction

Since the announcement of the trex something like 18 months ago there has been a continual search for that great power combination. There are many power systems now available for the trex which provide really excellent power and make the trex a lively and fully 3-D capable machine. Whilst I personally run a 4S machine the majority of fliers run 3S. Good 3D power can be extracted from a 3S system and this test is looking at the average setup for good 3D. I will not be looking at 3000 RPM head speeds in this test and instead have limited the pinion selections to hit around 2800 RPM. Also because of amp draw concerns no motor has been overly governed back or over pinioned so consequently there is a little variance in the starting head speeds.

In this test I am not looking at trying to create maximum flight time. This test is looking to define which motor(s) provide the maximum power for 3-D flight with a secondary consideration to amp draw and efficiency. All using a standard 2000mah 3S pack.

Equipment

Before we move into looking at the test data I would first like to introduce the various motors that have taken part in this test. I would also like to credit the various suppliers whose motors are participating in the test. Additionally, I need to detail exactly what pack has been used in these tests and what speed controller. Following this I will explain how the test was conducted and give some explanation to the charts that have been produced.

Motor	kv	Supplier	Pinion	Shaft size
Airpower 400DH	4000	Sussex Model Center	8T	2.3mm
RC-Zpower 450CE	3900	RC-Zpower	9T	2.3mm
JustGoFly 450F / RC-Zpower 450F (both tested, data was identical)	3450	JustGoFly	11T	2.3mm / 3.17mm
JustGoFly 450DH	4200	JustGoFly	8T	2.3mm
HeliDirect 450HDX (referred to as the HeliDirect 450TH in the charts)	3000	HeliDirect	13T	3.17mm
Align 430L	3550	Wattsuprc	13T	3.17mm
AON 3500	3500	Aon Motors	11T	2.3mm
Hyperion HP-H2220-04	not specified	Aircraft-World	13T	3.17mm
RC-Zpower 450TH / JustGofly 450TH	3000	Wattsuprc	13T	3.17mm
Lehner 1020/17	3500	FlightPower	10T	3.17mm
Medusa 28-32-2800	2800	Aurrora	13T	3.17mm
Medusa 28-40-2500	2500	Aurorra	15T	3.17mm
Medusa 28-40-3400	3400	Aurorra	11T	3.17mm
NEU 1105-3Y	3500	TPpacks	11T	2.3mm
NEU 1107-2Y	3400	JAQ (TrexTuning reviewer)	12T	2.3mm

*note: The RC-Zpower 450TH and JustGoFly 450TH are identical motors, the one in this review is an RC-Zpower 450TH. Both the RC-Zpower and JGF 450TH are identical for performance, RC-Zpower are the manufacturer of this motor and the supplier to JGF for their 450TH. Wattsuprc continue to supply this exact motor through their web site and this information is stated here as there was some confusion regarding this. This is not a clone motor or underpowered variant of the 450TH.

*note1: The article discusses the Helidirect 450TH the motor supplied was the 450HDX

The lithium polymer pack used throughout this test was a Kokam Cellpro 3S 2000mAh 15C. This pack was used with a FMA SkyVolt 6S fast charger. This pack was specifically selected because of its excellent thermal capabilities, good voltage hold and the ability to recharge in 20 minutes (at 3C). The speed controller used in this test was a castle creations 35 amp. This speed controller was selected due to its popularity.

The test equipment used in this test was a Medusa Power Analyser Pro. This was fitted with the infrared RPM sensor. I also used a Hyperion Emeter to double check the recorded data.

The test machine was my own personal machine, which is fitted with a Heliup carbon frame, Microheli QNC rotor head and Hyperion Diamond rotor blades. This machine is also fitted with the Microheli delrin main gear this is far more durable than standard gears but more importantly it is round. Having a perfectly round gear made setting gear mesh a very simple operation and also put less load on the motors during operation.

My thanks to Aurrora for the supply of the Cellpro Pack & SkyVolt Charger

My thanks to FlightBox for the supply of the MicroHeli Precision CNC Main Gear

The Test

The motor test consists of four phases. The first phase is an initial spool up to operating RPM. I set all of the motors to run at around 3000 rpm with approx 2° of pitch on the blades. The initial spool up is one minute operating at 3000 rpm with 2° pitch on the blades. The second phase of the test is the application of 10° of positive pitch for the duration of 20 seconds. This is the main loading part of the test and is designed to ascertain what RPM the motor can hold at full pitch at the end of 20 seconds. The third phase of the test the motor is given a 10 second rest at approx 2° pitch. The fourth phase of the test consists of 30 seconds pitch pumping from -10° to +10°. At the end of this phase the test is complete and the motor is checked to make sure it has not hit an excessive temperature (over 80° C.). The following table summarises the test.

Phase	Activity	Duration	Start Time on Graphs	End Time on Graphs
Phase 1	Spool Up to 3000 RPM at 2° pitch	1 minute	0 minutes	1 minute
Phase 2	10° positive pitch	20 seconds	1 minute	1 minute 20 seconds
Phase 3	Approx 2° positive pitch	10 seconds	1 minute 20 seconds	1 minute 30 seconds
Phase 4	Pitch pumping	30 seconds	1 minute 30 seconds	2 minutes

 

I should point out at this stage that none of the motors tested went over the control temperature of 80° C. Therefore I will not mention this further in the test results.

The Charts

The following is an explanation of the charts used to differentiate the performance of the various motors. I will use the charts generated by the 450TH motor to explain how to interpret the charts.

Below is an amperage chart for the 450TH. The first 20 seconds of the chart show a spike in amperage as the motor initially spins up. Following this up to the one-minute mark the motor is running constant at 2° pitch. There is then a large increase in amps as I apply 10° of pitch for 20 seconds. The motor is then rested for 10 seconds at 2° pitch. Following this you can see a number of spikes in amperage as I pitch pump the helicopter until the end of the test.
As can be seen from the chart the 450 TH hit a maximum of 23.67 amps at the initial point that 10° of pitch was applied. During the pitch pump we have a fairly consistent amp draw for each pump. Also I can see from this chart that this motor is fairly easy to govern as the chart doesn't have any spiking at the points with the motor is running at 2° pitch. During the full pitch 20 seconds you can see that the amperage required slowly decays to approximately 22.5 amps, this decay in amp draw is due to the head speed slowing down and therefore less power is required.

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The following chart is from exactly the same test as the above but this time showing the RPM during the test. This chart shows a very minor decay in head speed during the one-minute spool up. Following this the 10° of pitch is introduced and the head speed drops to 2225 rpm. A recovery in head speed is then seen during the 10 seconds that the motor is at 2 ° pitch. Following this we can see fluctuations in head speed during the pitch pumping of approximately 75 rpm. Also we can see that the 450 TH did not return to the 2825 rpm originally set for head speed and that the pitch pumping average head speed was around 2475 rpm.

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Within the context of this super test I will display data for several motors on one chart. This allows a direct comparison of the motor performance as they are put through exactly the same test. I will work with only three or four motors at a time on each chart so that the data does not get overly confusing.

So, let's move on to the first section of the super test. The first part of the test results will look at the relative amp draw of each motor.

Amp Draw

This part of the test will focus on the amp draw of the various motors as they are put through the standard test. The amp draw consumed by the motors in isolation does not give an indication of the performance of the motor. The set of charts that follow give an indication of what sort of flight time one might expect to get on each motor. The data also shows how hard the pack will be pushed to deliver the performance. The amp draw needs to be compared to the RPM performance in order to get an indication of efficiency. I will do this comparison later in the test.

The following chart shows the four worst performing motors in terms of amp draw. In other words all of these motors are the ones that demanded the most amps over the course of the test.

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As can be seen from this graph the Hyperion and 450DH motors are the most hungry in terms of amps demanded. During the full pitch test the Hyperion demanded 38.09 amps and the 450DH was even more demanding with a 38.64 amp demand. During the full pitch test you can see that there is quite a steep slope on the amps which is due to the pack suffering from voltage drop due to the heavy demand being placed upon it. That drop in voltage is mirrored by a drop in the amp demand. The maximum continuous current that the pack could supply was 30 amps and you can see a less steep slope on the two motors demanding below 30 amps during the full pitch test. The 450DH actually pulled the pack into the ESC voltage shutdown range of 9V and the spikes are the ESC switching in and out of shutdown.

It is important to remember that the amps demanded could very well be justified given the performance returned by the motors. We will see later in the test whether this high amp demand was justified in the performance returned from the motors. Also in flight these figures would be lower as the model will be moving through the air rather than pushing static air through the blades.

Let's now take a look at the motors that placed midfield in terms of their amp demand. This is split into the lower and upper midfield. First the lower midfield.

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All of the above motors did not demand beyond what the pack could deliver and would provide a reasonable flight time on an 1800 or 2000mAh pack. Again we have to compare this amp draw to the relative performance delivered by the motors to ascertain whether it is a justifiable demand for the performance given.

The next set of motors are the upper midfield in terms of amp draw. These motors will give a better return in terms of flight time. Although again we have to contrast this with performance to see if the efficiency is worth having.

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Note the Lehner and Medusa which are tracking each other quite closely in this part of the test. The Aon shows a very frugal set of figures overall compared to it's peers in this group.

Lastly we have the amp draw winners which were the most frugal in terms of amp draw. Although with this level of efficiency we may be sacrificing performance.

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All of the above motors do not stress the pack at all and one of these motors manages to break below 11 amps to deliver a 2800 rpm head speed. If we consider that all of these motors are being asked to turn 325 mm carbon blades at 2700+ rpm the above results really are excellent in terms of efficiency. The outright winner in the amp draw test being the Medusa 28-32-2800.

This concludes the first element of the test and we have our initial first-place motor which is the Medusa 28-32-2800.

The next part of the test will look at the RPM held during the 20 seconds of full pitch.

RPM Held

This part of the test is looking to see how well the motor will hold a sustained heavy load. In this case plus 10° of pitch at full throttle. The expectation is that the head speed will slowly decay over the first 10 seconds or so and then the motor should hold at a specific RPM. It is the RPM at the end of the 20 seconds which differentiates one motor from another. The factors that come into play here are the heat generated whilst the motor is under load and the ability of the motor to deal with that increased heat. A good motor will hold a higher RPM and generally will generate less heat during the 20 seconds. Another important factor is how the motor recovers once you remove the load. Some motors will return to the rpm initially set, other motors will not do this. The demand placed on the pack also comes into play in this test. If the pack has been heavily loaded (beyond specification) then it may not be able to supply the required voltage immediately in order to return the motor to it's original rpm once the load is removed (i.e. once the pitch is reduced to 2°)

So, let's take a look at the bottom four performing motors for the full throttle, full pitch test.

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If you've been paying attention you will have noticed that two of the top motors for amp draw are amongst the bottom four in terms of RPM held under load. So immediately we can see that although these motors are very good on amp draw they aren't giving the best performance. This is not a revelation and is very much to be expected. We will need to look deeper in order to find the motors that are giving good performance and good amp draw characteristics. Also worthy of note is that the NEU motor which returned to close to the original head speed once the load was removed. The other three motors suffered some loss in head speed at the end of the full pitch test. Let's take a look at the lower midfield in terms of RPM held.

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The above three motors are all delivering in the 2175-2200 RPM range under full load. This is a good performance by any standards, even some of the top performing motors are only around 75 RPM away. The motors were all very close on this particular test. Note the excellent recovered RPM on the 450DH and also on the Lehner after the end of the full pitch test. This is a good measure of the motors ability to handle heat and not deteriorate under load.

Let's now take a look at the upper midfield performing motors for RPM held under load.

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The upper midfield motors were all incredibly close with only 25 RPM separating top from bottom. The differentiating factor being in the RPM recovery on these motors. All the motors delivered close to 2225 rpm at full pitch. Notable in it's ability to recover RPM amongst these upper midfield motors was the NEU 1107 with only a 75 RPM overall drop. All four of these motors really have outstanding power delivery and little separates them from some of the top performing motors in the test.

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Finally we have the top three. The two Medusa showing almost identical performance and the Hyperion putting in a staggering performance and beating all comers by 75RPM.

Of course if we go back and look at the amp draw figures we can also see that the Hyperion demanded a fairly staggering number of amps. RPM recovery on the Hyperion was superb, the Medusa also put in a very good performance in this area.

So let's move on to the pitch pumping section of the test.

Pitch Pumping

This part of the test is where the motors are pitch pumped for 30 seconds from -10° to +10°. What we are looking for in this part of the test is for a consistent RPM fluctuation across the 30 seconds. We are also looking for the smallest possible fluctuation in RPM as we want the machine to maintain as much head speed as possible. What we should not see is a slowly decaying head speed across the 30 seconds. We also do not want to see large drops in RPM. The pitch pumping starts at 1 minute 30 seconds on all the charts and is the last (spiky) part of the graphs before spool down. Consistency is the name of the game.

So let's take a look at the bottom for performing motors in this section of the test.

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What we can see for the bottom performing motors is that the head speed has dropped down into the 2350 to 2450 RPM range. RPM fluctuation is between 50 and 150 RPM. We can also see a slight decay in head speed from the beginning of the test to the end of the test. All four motors really gave a very similar performance in terms of RPM fluctuation and head speed.

Let's take a look at the lower midfield for the pitch pumping section of the test.

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Amongst these four lower midfield motors the Zpower 450TH and HeliDirect 450TH show the most consistent results with a slight decay in head speed across the test. RPM fluctuation on these motors being 75 rpm. The other two motors were less consistent. All four motors are sitting at around 2400 to 2525 rpm during the pitch pump test.

Let's look at the upper mid four motors.

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The two Medusa motors have a fairly flat and consistent pitch pump with little or no decay in head speed. The Lehner has a good RPM recovery on each pump but it is lacking in torque which gives it quite a wide rpm range of 125 rpm. This lack of torque creates a larger head speed loss at the peak of each pitch pump. The NEU shows a decay in head speed from the beginning of the pitch pump to the end which is quite noticeable in the graph.

Let's take a look at the top three motors for the pitch pumping section of the test.

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The Hyperion HZ2220-04 the clear winner in this section of the test and is fluctuating 25 RPM per pitch pump. This motor also manages to maintain the 2750 rpm head speed set for it at the start of the test. The 450CE and 450DH are similarly consistent with a nice flat pitch pump. These motors maintain head speed at around 2550 to 2675 rpm during the pitch pump. The fluctuation on these two motors is around 50-75RPM.

Before we consider efficiency the following ranking is for those who care nothing for amp draw and are just interested in out right performance.

Fourth Place : Zpower 450CE
Third Place : Medusa 28-40-2500
Second Place : Medusa 28-40-3400
First Place : Hyperion HZ2220-04

However there is more to performance than just outright grunt. However, for those just interested in grunt here are the charts for the first and second place most powerful motors. These are not at this point test winners, just the most powerful motors on test regardless of amp draw.

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Before moving onto the next section of the test here is a summary table showing the tabular data for each motor.

Motor	Initial RPM	2° Pitch Amps	Max Pitch Amps	Max Pitch RPM Held	Recovered RPM	Pitch Pumping Amps peak	Pitch Pumping Low RPM	Pitch Pumping High RPM	Pitch Pumping RPM Fluctuation
Airpower 400DH	2725	15.4	27.96	2100	2600	25.84	2400	2475	75
Zpower 450CE	2875	17.84	33.67	2225	2775	31.25	2550	2625	75
JustGoFly 450DH	2850	21	38.64	2175	2850	37.1	2625	2675	50
JustGoFly 450F	2800	13.62	28.79	2225	2650	28.54	2400	2500	100
HeliDirect 450HDX	2775	15.67	26.46	2175	2675	23.81	2450	2525	75
Zpower 450TH	2825	11.85	23.67	2225	2725	21.8	2450	2525	75
AON 2815-3500	2775	11.92	25.04	2175	2700	24.78	2375	2525	150
Align 430L	2925	15.68	28.79	2125	2775	27.16	2350	2450	100
Hyperion HZ2200-04	2750	16.13	38.09	2350	2750	37.06	2675	2700	25
Medusa 28-40-3400	2825	14.49	27.56	2275	2775	27.68	2500	2550	50
Medusa 28-40-2500	2800	14.29	26.78	2275	2725	26.18	2500	2550	50
Medusa 28-32-2800	2725	10.89	22.51	2150	2625	21.5	2350	2400	50
Lehner 1020/17	2850	13.91	27.03	2200	2800	25.8	2475	2600	125
NEU 1105-3Y	2700	11.91	22.09	2150	2675	22.41	2375	2475	100
NEU 1107-2Y	2800	13.63	27.11	2250	2725	26.97	2450	2550	100

 

That concludes the source data we can now use to analyse the efficiency versus performance of each motor. Based on this we should then be able to identify which motors provide the best power for the least amp draw. This is a more complicated comparison than the previous charts. However we must use the charts and this data to draw the overall winners. The tabular data shows snapshot data where as the graphs show trend data for each motor. Together these create the required information to pick overall winners.

Efficiency Analysis

I could at this point just select the highest performing motor and ignore the amp draw characteristics. However, whilst this may be the right thing to do and fit some people's requirements I don't think it represents the best choice of motor. If you are not concerned about amp draw and are purely concerned with performance then the Hyperion HZ2220-04 is the top performing motor.

Personally I would want to make sure that I'm getting great performance but equally maximising my flight time as well as taking care of my pack. This is where it is worth taking a couple of moments to talk about the amp draw from these motors.

The test is conducted with the helicopter strapped down. This means that during the test the blades have to move static air. The motor is having to work significantly harder than if the model was moving through the air. This effectively pushes up the amp draw requirements during the test. In flight all of these motors will pull less amps, suffer from less head speed drop and generally perform better. We need to keep this in mind when looking at the figures and assessing whether the motor in question is suitable for our requirements.

First we can narrow the field of motors that we are looking at by selecting the top six performing motors from an RPM point of view. The following motors are not being considered as overall test winners based on this:

Aon 2815-3500
Align 430L
NEU 1105-3Y
Airpower 400DH
Medusa 28-32-2800
JustGoFly 450F
HeliDirect 450TH

Whilst these motors do provide good performance they are at the lower end in this test and therefore not potential test winners. The HeliDirect 450TH is eliminated on the basis that it performed exactly the same as the Zpower 450TH but demanded more amps to do so.

We can also take a look at the high amp draw motors in this test as they also may not be overall winners due to their larger amp draw requirements.
Therefore the following two motors are also not considered to be overall test winners:

Zpower 450CE
Hyperion HZ2220-04
JustGoFly 450DH

This leaves me with five motors to compare with regard to performance and efficiency.

Lehner 1020/17
Medusa 28-40-2500
Medusa 28-40-3400
NEU 1107-2Y
Zpower 450TH

So let's get these five on a chart and see what's going on.

Final Selection

The final selection for the overall winner is very difficult. All of the motors below have delivered an outstanding performance. As you can see from the graphs they are very close in terms of their performance.

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With five motors it's quite difficult to see what is going on but the basics are that the 450TH has the weakest performance on RPM, followed by the Lehner. The two Medusa motors show the strongest performance and consistency. Both the 450TH and NEU show a degradation is their abilities over the course of the 30 second pitch pump. The Lehner is weak in the full pitch test and to some extent suffers from a lack of torque in the pitch pumping with 125 rpm fluctuations compared to the Medusa's 50 rpm variation.

Let's now take a look at the amp draw of these motors in comparison.

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In the amp draw comparison we can clearly see the 450TH as having the lowest draw but the separation is only on average 4 amps, which isn't a huge margin. The 450TH also has the weakest performance from an RPM point of view from the previous chart. All of the other motors are so close as to not really make a deciding difference. The NEU is the next most efficient but the margin from the other motors is minimal.

Next we need to consider weight and price.

Weight & Price

The last consideration with regard to performance is the weight of the motor. In this section I will also include an indicative price for each of the motors. Although price has little to do with performance it is a selection criteria when choosing a new motor. The following table summarises the weight and price of the various motors on this test.

Motor	Weight (g)	Price ($)
AirPower 400DH	42	49
JustGoFly 450DH	57	unknown
JustGoFly 450F	57	56
Zpower 450CE	57	56
HeliDirect 450HDX	57	38
Zpower 450TH	57	56
AON 2815-3500	98	75
Align 430L	58	45
Hyperion HZ2200-04	87	tba
Medusa 28-40-3400	100	80
Medusa 28-40-2500	100	80
Medusa 28-32-2800	70	80
Lehner 1020/17	73	150
NEU 1105-3Y	65	90
NEU 1107-2Y	100	119

 

We can see that three of the top five motors all weigh in at 100 g and therefore have no particular performance advantage over one another. The 450TH only weighs 57 g and therefore will benefit from some in-flight weight savings over the other motors. The Lehner is 73g and therefore will gain a small benefit from weight savings.

If we take a quick look at price amongst these top five performers we can see that there is a premium to pay for the NEU1107-2Y and the Lehner 1020/17 where as the Medusa motors are cheaper and the 450TH is the cheapest.

Other Observations

During the course of this test there were several other things that came to my attention. Firstly most of the motors were quite happy to run using the Castle Creations governor. Notable exceptions to this were the JustGoFly 450DH and the Hyperion HZ2220-04. These two motors were definitely not happy and some fluctuation in RPM can be seen on the graphs during spool up phase.

Whilst testing the Lehner I was about whether timing was accurate to verify this I ran the test using a Jazz speed controller. The power produced was exactly the same but interestingly the amp draw was higher when using the Jazz controller.

 

Conclusion

As with all tests it eventually becomes necessary to pick the winner. Listed below are my personal choices based upon the data gathered.

Fourth Place : Lehner 1020/17
Third Place : NEU 1107-2Y
Second Place : Zpower 450TH
Joint First Place : Medusa 28-40-3400 & Medusa 28-40-2500

The Medusa motors are awarded first place on the basis of their excellent power delivery, reasonable amp draw and superb consistency in the various tests. In particular I was impressed with the little extra power of these motors in comparison to their peers but at minimal costs in terms of amp draw. Their performance is so close on the test that it didn't seem right to place one ahead of the other. The Medusa out performed the 450TH in every area of the RPM test and the price is on average 4 amps.

The second place motor is the Zpower 450TH which although not quite having the performance sparkle of the Medusa motors or consistency makes up for it in price, weight and amp draw. For the budget conscious buyer this is a superb motor and will turn in a very respectable performance at 4S as well. For anyone placing a high importance on amp draw this motor would be the one of choice.

One thing to note is that the separation between the 450TH and the Medusa motors widens as you increase the head speed, so at 3000 RPM the 450TH from a performance perspective copes less well than the Medusa motors. This is evidenced in the performance decay shown in the charts as the test progressed. The Medusa motors did not exhibit this decay in performance. In other words the Medusa have more to give should you ask it of them. Similar to the 450TH they also will perform extremely well at 4S giving them a nice versatility.

The NEU places third as it couldn't quite keep up with the Medusa and exhibited a similar performance decay to the 450TH, however the 450TH makes up for this in price/weight/efficiency where as the NEU doesn't. In many respects the NEU makes a far better 4S motor where the extra power can offset it's weight.

The Lehner places fourth. It is characterised by having a very good throttling response but due to it's diminutive size doesn't quite have the necessary torque. This led to disappointment in the pitch pump and max pitch tests.

I have placed the winner and runner up on three charts, one showing Amps, one showing RPM and one showing Watts of power delivered. Due to the joint first place and the similarity in the data I have just included the data from the Medusa 28-40-2500.

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Lastly, my thanks to all the suppliers who made this test possible by providing not only motors but lithium packs, test equipment and their expertise in helping me get the best out of their motors.

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