All-New Freewing PJ50 Twin 70mm EDF Jet - Official Thread

[BigJim]

I always harass James for new product news and was glad to jump on this one as soon as the pre-order hit the site. Thanks for hitting a wish list item for me! I will be painting mine as a C-37A... only wish I could find the tail number(s) stationed at Hickam 1998 - 2000. If not, I know 10065 or 60500 were there later.

[GliderGuy]

Something to consider (possibly overkill depending upon your flying style and typical flying air temperatures)...

(Photo below) I see that the ESCs are mounted in the rear tail cone. Thus, as with the AL37, cooling air only flows over them when the jet is in motion.

This design leads to a few things which you may be getting prepared for....as learned from my AL37 (summertime days get HOT here)::

1. Running down the batteries while stationary isn't a good idea. The ESCs get hot and heat is problematic for electronics. They'll last longer if you keep them cooler.
2. If you must run down the batteries while on the ground, get some cooling air flowing into the ESC compartment.
3. I built a cooling fan from a high volume/rpm, 24-volt DC PC case fan attached to one end of an old 6S battery and added a switch.
4. The AL37 sits low enough so I place this cooling fan+battery assembly on the ground under the AL37 and blow air up onto the ESCs.
5. Since typically I strive for a short down time between flights...as soon as the AL37 lands and taxis back, I put the cooling fan assembly under the bird and begin blowing air over the ESCs while I change the battery.

I see that the PJ50 ESC compartment is high up and located on the underside of the tail cone. This will require building a small shelf for the fan+battery assembly to get the assembly high enough off the ground to effectively blow cooling air into the ESC compartment.

Alternatively, when the bird arrives, I am going to evaluate this area and determine whether or not there is sufficient room to mount a small cooling fan in there that will be circulating air any time the main battery is connected. DC fans don't draw much current at all.

Overkill....possibly. But electronics are happier when they are cooler. And, I have had an ESC shut down on me due to overheating while running down batteries on the ground when I could not fly off the charge.

-GG

Screen capture from the announcement video...

[ridgerunner]

So if the AL-37 is a Boeing 737 Max, (nod, nod, wink, wink), what is the PJ-50?
Cessna? Lear?

[Gilatrout]

So if the AL-37 is a Boeing 737 Max, (nod, nod, wink, wink), what is the PJ-50?
Cessna? Lear?

Gulfstream

[GliderGuy]

So if the AL-37 is a Boeing 737 Max, (nod, nod, wink, wink), what is the PJ-50?
Cessna? Lear?

A close match…

[xviper]

1. Running down the batteries while stationary isn't a good idea. The ESCs get hot and heat is problematic for electronics. They'll last longer if you keep them cooler.

People actually do that? I can see doing it momentarily for watt and amp measurements but just running it to drain the batteries down? I just take them home and put them on the dis-charger OR drive them up and down the runway a couple of times.

[GliderGuy]

People actually do that? I can see doing it momentarily for watt and amp measurements but just running it to drain the batteries down? I just take them home and put them on the dis-charger OR drive them up and down the runway a couple of times.

Ummm….Yes.

Consider 4 min of runtime on the ground at cruise power vs sometimes hours on a discharger vs who knows how many trips up and down a runway at taxi power (a lot of taxing…more than a few trips) to use 60% to 70% of a 6000 mAh cell and reach the recommended 3.8 V storage voltage. Assuming a 10 amp draw at taxi power = almost half an hour of taxi trips (just a guess = 10 A). And I have 10 batteries to discharge if the weather turns bad.

I’ve done it and learned it isn’t a good idea when the ESC shut down. If I do it now, I supply cooling airflow to the ESCs on birds that don’t have the ESC mounted in the engine airflow stream or propwash stream.

Call it….Lessons learned and passed along for the edification of others.

Best way….Use the MiG-29!!! 2 batteries at a time and ESCs mounted in the fan’s airflow stream. 10 batteries discharged in 20 min without any ESC overheating concerns.

-GG

[Bajora]

[Evan D]

Yes, the "other" contender...

[avanti127]

This thing is going to be a rocket and will sell like hotcakes. I think they've read the room brilliantly. Great job guys.

There's a decade long back catalogue of military EDFs for people to work through.

As for pricing, I heard the US is nudging 7% inflation? And you're gonna benchmark price against planes released years ago? Come on.

I agree with you. The market is pretty saturated with Military aircraft and it's about time we get civilian jets into the mix.

[avanti127]

Something to consider (possibly overkill depending upon your flying style and typical flying air temperatures)...

(Photo below) I see that the ESCs are mounted in the rear tail cone. Thus, as with the AL37, cooling air only flows over them when the jet is in motion.

This design leads to a few things which you may be getting prepared for....as learned from my AL37 (summertime days get HOT here)::

1. Running down the batteries while stationary isn't a good idea. The ESCs get hot and heat is problematic for electronics. They'll last longer if you keep them cooler.
2. If you must run down the batteries while on the ground, get some cooling air flowing into the ESC compartment.
3. I built a cooling fan from a high volume/rpm, 24-volt DC PC case fan attached to one end of an old 6S battery and added a switch.
4. The AL37 sits low enough so I place this cooling fan+battery assembly on the ground under the AL37 and blow air up onto the ESCs.
5. Since typically I strive for a short down time between flights...as soon as the AL37 lands and taxis back, I put the cooling fan assembly under the bird and begin blowing air over the ESCs while I change the battery.

I see that the PJ50 ESC compartment is high up and located on the underside of the tail cone. This will require building a small shelf for the fan+battery assembly to get the assembly high enough off the ground to effectively blow cooling air into the ESC compartment.

Alternatively, when the bird arrives, I am going to evaluate this area and determine whether or not there is sufficient room to mount a small cooling fan in there that will be circulating air any time the main battery is connected. DC fans don't draw much current at all.

Overkill....possibly. But electronics are happier when they are cooler. And, I have had an ESC shut down on me due to overheating while running down batteries on the ground when I could not fly off the charge.

-GG

Screen capture from the announcement video...

No different than the AL37 ESC location and never had an issue. Plus they said it was tested for almost year in hot climates.

[GliderGuy]

No different than the AL37 ESC location and never had an issue. Plus they said it was tested for almost year in hot climates.

Details of the testing are unknown, but I'm glad to hear that.

However, the points of my post were #1, FACT: I had an ESC stop working/shut down during a hot day ground run w/o any cooling air flow (stupid of me). and #2 FACT: Any electronics will last longer if you take care to keep the operating temperature down.

What I can state is that making a lot of flights on hot days with very little down time between flights AND all this flying has been done with cooling the ESC with the external PC case fan while the battery is being changed has given me good results (i.e., no more ESC failures). I prefer to have the maximum amount of margin possible.

Bottom line, if you're gonna get the PJ50 AND you fly in hot climates AND you do a lot of flights with little cool-down time between flights....you have another data point to reference.

-GG

[avanti127]

I am going with the classy look.

[Twowingtj]

avanti127 That's pretty sweet.

[avanti127]

Details of the testing are unknown, but I'm glad to hear that.

However, the points of my post were #1, FACT: I had an ESC stop working/shut down during a hot day ground run w/o any cooling air flow (stupid of me). and #2 FACT: Any electronics will last longer if you take care to keep the operating temperature down.

What I can state is that making a lot of flights on hot days with very little down time between flights AND all this flying has been done with cooling the ESC with the external PC case fan while the battery is being changed has given me good results (i.e., no more ESC failures). I prefer to have the maximum amount of margin possible.

Bottom line, if you're gonna get the PJ50 AND you fly in hot climates AND you do a lot of flights with little cool-down time between flights....you have another data point to reference.

-GG

I agree on the down times. I always wait between flights anyway that's why I take at least two bird with me to the field.

[JLambCWU]

A little more durability testing footage that Jeremy Solt and I grabbed while evaluating the new PJ50 for Motion RC.

Motion takes product quality seriously and wants to offer the best products to its loyal customer base. Just one of top speed testing passes to see if we could pull it apart. 139mph over the ground!

[Hugh Wiedman]

Ummm….Yes.

Consider 4 min of runtime on the ground at cruise power vs sometimes hours on a discharger vs who knows how many trips up and down a runway at taxi power (a lot of taxing…more than a few trips) to use 60% to 70% of a 6000 mAh cell and reach the recommended 3.8 V storage voltage. Assuming a 10 amp draw at taxi power = almost half an hour of taxi trips (just a guess = 10 A). And I have 10 batteries to discharge if the weather turns bad.

I’ve done it and learned it isn’t a good idea when the ESC shut down. If I do it now, I supply cooling airflow to the ESCs on birds that don’t have the ESC mounted in the engine airflow stream or propwash stream.

Call it….Lessons learned and passed along for the edification of others.

Best way….Use the MiG-29!!! 2 batteries at a time and ESCs mounted in the fan’s airflow stream. 10 batteries discharged in 20 min without any ESC overheating concerns.

-GG

Just an idea, as I also used to discharge batts occasionally with a twin EDF, but then RudyD54 turned me onto the ISDT 200W Discharger. Takes about 15 minutes to discharge a 6200mah 6S fully charged to 3.84 volts per cell, or whatever you set it to discharge to. It can hook up to your phone and control it from there or just by hitting a couple buttons on the unit itself. Discharges 2S-6S up to 25A/200W, or again whatever you set it to do. Comes with a fan and saves me tons of time if I don't discharge a battery to a low enough storage value during flying or sometimes have to leave with a fully charged battery (yes, that's sacrilegious). It doesn't balance discharge but you set the level you want to discharge to, then at home I put the batts on my charger to balance storage charge to 3.85 V per cell. Can get it at multiple outlets for about $79. I can charge up to 8 6S batts with my current set-up, but unfortunately the discharge function I have is lame at .5Amps and just about the time "hell freezes over" is when it's finally done! Was thinking about getting a 2nd one but so far one has been sufficient.

Now I can't discharge 10 in 20 min like you do with the Mig, but I'll discharge some at the field while packing up, put some on in the truck on the way home so by the time I home, I'm done. Also didn't like putting "extra hours" on any of the EDF's or ESC's.

[Evan D]

I have a discharger too, great item.

[killickb]

I would think that the "other contender" would be the yet to be released Xfly version of a twin 70mm Gulfstream. At the risk of loosing a spot in the first F/W batch, I am waiting to be able to compare the two Gulfstreams. Have many F/W jets so i know that the quality will be there. Also fly the Xfly Sirius and it has provided me with equal quality and flight performance as my F/W models. Love the competition driving ever better models into our fleets.

[GliderGuy]

Hi Evan and Hugh….
Thanks for the discharger info. However, I rarely need to discharge. And, when I do….sometimes it is all 10 6S batteries and 6 4S batteries. That’s a lot of dischargers and discharge cycles.

As much as I fly, a few more runs on the ESCs and motors is a drop in the bucket regarding usage.

Interesting note….over thousands of flights across all my birds…only one AL37 motor bearing has started to squeal. That’s amazing! MRC offered to replace it. Love MRC customer service!

Avanti127…Regarding downtime / Three birds out to fly = 6 or 7 flights with the AL37 with little down time, then 4 or 3 on the F-4 then 3 on the P-38. By then the first set of batteries are ready and the AL37 goes back up for 6 or 7 more…little down time. 16 batteries and 3 400 W chargers keep me going. AND a good alternator on my truck. I know….I’m nuts. But I love to fly (40 flights in a day with lunch and bio breaks is my record). If I flew at a club, they’d kick me out for hogging the airspace. LOL.

I tend to find the design limits of things.

My point...I do stress the AL37's ESCs and perform thermal management with an external fan during battery changes to keep things cooler to help ensure the electronics last longer. Those who fly in hot weather and don't have cooling-off periods between flights would be wise to also do things to remove the heat from the PJ50's ESCs. Just common sense care of electronics.

JLamb….She’s a screamer! Thanks!!!

-GG

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