Quad racing motors in Park Jets, Part 1 - Initial lessons learned

Hi Everyone -

For those of you who have been following my YouTube channel, I have been on a mission to experiment using quad racing motors in park jets for the last several months.  I am certainly not a pioneer in this, several other folks around the RC Powers forum have been experimenting with them and even designing planes that use them, however mostly in a twin or two motor setup.  Either the motors are set into the wing or other part of the fuselage or attached to the elevons to have full power thrust vectoring.

So it got me to thinking and doing some research scouring YouTube and many vendors looking for motors that might be useful in a standard single motor setup on 3S.  I know this is quite the challenge I have set for myself as from what I learned most folks who race quads are on a 4S setup or maybe higher.

Fortunately, rcplanepirate (RCPP) from the UK has done a lot of testing on different size quad racing motors, so that really helped me make decisions on which motors to try.  I would encourage you to check out RCPP's YouTube channel, he is a very knowledgeable gent and very helpful, every time I have asked him a question, he has been very prompt and thorough in his response and I have learned a lot from him about brushless motors in a short period of time.

I have created a Google Doc listing all the motors I have ordered along with some 5" three bladed quad props I might try.  I'll be writing another article on each of the motors and why I decided to buy them to test.  I have already received the first three motors from RC Timer and have bench and field tested all of them.

Thus far, the biggest advantage I see in using quad racing motors in my park jets is that they are quite a bit lighter than the standard 2212 2200 Kv motor which with prop and hardware weighs around 67 gr/2.4 oz.  The heaviest quad motor I have tested thus far weighs 52 gr/1.8 oz, so already 15 gr/0.6 oz of weight saved.  I know this might not seem like a lot, but more on my thought process in a bit.  Most of the quad motors are not as efficient (ie they have higher amp draw for the same thrust produced) as the 2212 2200 Kv motors, but they definitely "punch above their weight".

Other advantages of experimenting with quad motors is that the technology is improving at a rapid rate as this is such a popular and fast growing part of the hobby.  From research I have done, often what was the "hot" motor three months ago is no longer as manufacturers are constantly developing lighter, more powerful motors.  Also, because there are so many different manufacturers trying to get a piece of this very active market, the selection is pretty incredible compared to the park jet motors that have been popular since I got into this hobby seriously over 5 yrs ago.  The 2212 2200 Kv motors I use now are the same as they were ten years ago, I can just get them for cheaper as more "knock offs" are made all the time.

What this competition in the quad motor market means is that although these motors are a bit more expensive than other popular choices, they often go on sale.  Since they are designed primarily for quads, you can often purchase packages of 4 motors at a time at a reduced unit price if you find a motor you really like and want more than one of them.

I won't get too in depth about the motors and their specs in this article, I want to share some lessons learned about selecting and building a park jet if you specifically want to use a lighter, smaller quad racing motor in your plane.

Although I have some slightly bigger motors with higher Kv on the way to test, they are all physically smaller than a 2212 2200 Kv motor, normally half as tall or even less in the case of the 2205 size motor.  From my research and experience, lack of torque in the smaller motor can be made up for somewhat with an increase in Kv with the right prop, but facts are facts, they are just physically smaller motors with some limitations as a result.  I will continue to update my thoughts and lessons learned as I go through this process, however I think much of what follows will continue to apply.  I certainly don't think I will be replacing every motor I currently own with a quad racing motor, rather choosing the right plane to match the right motor😊

Plane choice

I think to set yourself up for the best chance of success, choosing the right "weapon" will be important.  Thus far I have only flown a NAMC Mig-35B and an RC Powers F-22 V5 with quad racing motors, both of which are pretty sleek and fast airframes regardless of the power system.

As I get some more powerful quad motors, I will be testing one in a more "draggy" plane, the F18 V5, although still pretty fast, it's more straight wing does create a bit more drag than the Mig, F22 or Sukhoi style wing.

I would also suggest that size of park jet will matter more with a quad racing motor, I like to fly planes with wingspans of 27" or very close to that, so I would be hesitant to try one in a larger park jet with a wingspan closer to 30" or more for example.  Air frames like an F-35 for example may also be a challenge as they can be very "draggy" no matter what you do to them.

Build

After long being a card carrying member of the "overbuilder's anonymous" club😒, I have been striving for several years to build my air frames as light and as strong as possible to maximize performance and still stand up to my sometimes aggressive flying style.  Regardless of the foam or glue you like to use, I think it is vital to really concentrate on building as light as you can if you plan on putting a quad motor in a plane.

As you may have heard me discuss in my YouTube videos and in my recent review of the RC Powers F-22 V5, it is important to modify the leading edge of the prop slot to accept the considerably shorter quad motors.  Otherwise the plane will be noisy and the prop less efficient.  I find trimming about 3/8"/9.5 mm from the leading edge of the prop slot is sufficient.  Better to do this while building than to try and cut it out later.  Even if you decide not to go with a quad motor, your prop will have plenty of room to spin more efficiently.

Choosing the lightest ESC and servos will also help considerably.  If you can get away with a 30A ESC rather than a 40A ESC, you will normally save about 8 gr/0.3 oz.  I have been building and flying most of my planes with lighter 5 gr nylon gear servos for the rudders and ailerons and this has been working very well for me and compared to using 6 nine gram nylon gear servos in previous builds, I am saving another 20 gr/0.7 oz, so there is an oz saved right there between a lighter ESC and lighter servos.  I don't think I could ever bring myself to use 5 gr servos for my elevons, but if you are using metal gear servos now, you might want to consider trying nylon gear servos to save some weight for a quad motor park jet build.  I will be writing a more detailed article on my servo experiences in the near future.

I know I'm bucking my own philosophy here by flying with 2200 3S batteries, I could instantly save a couple of oz with a lighter battery and I will experiment with that eventually.  2200 3S batteries are what I have the most of and I like to have a certain amount of weight to give my planes the "feel" I like in the air.  Most of the year where I fly, the wind is 5-10 mph, so I like to have a bit of weight to prevent my planes from getting bounced around too much.  Thus far, a flying weight of around 20 oz/567 gr seems to be ideal for the testing I have been doing with the motors I have currently, as they get more powerful, this ideal weight may also change somewhat.

Reducing the drag profile of your plane as much as you can is also important to allow the quad motor to help give your plane it's maximum performance.  If you have access to thinner Dollar Tree Foam (DTF or Adams Readi-board), you might consider building your fuselage and wing plate with that to significantly reduce your drag profile over Model Plane foam or Depron.  Even if you can't get thinner foam, a good sanding job of your plane, tapering the leading and trailing edges of the wing, vertical stabs, horizontal stabs and elevons will all help to reduce the drag of your park jet and make it much "slipperier" through the air.

So the main lesson I have learned to set myself up for success with a quad motor in my park jet as mentioned is to focus on selecting a fast or efficient (low drag) air frame from the outset, build it light and treat it to a good finish job to keep it as sleek as possible😎

Much more to follow in the coming weeks/months as I continue on this journey experimenting with quad racing motors in park jets😊

Park Jet noise...the "other" sound of freedom😎

Cheers,

Scott