Overlapping props vs adjacent ones


#1

How would a pair of motors mounted laterally close together and whose props overlapped, perform with respect to thrust reduction if they were mounted without prop overlap?

Should counter-rotation be considered?

I do not know if the claim of increased thrust is true.

The props appear to be counter-rotating.

https://www.youtube.com/watch?v=6XE0–3A7gY


#2

Like this?


I built this last year but my build quality ain’t too flash. The cage was totally crap and I had no goose bars. When I tested it the risers pushed the netting into the top prop, you can see a chunk of it flying off.

I’ve stil got the parts and may have a go at building a MkII soon :slight_smile:

Regards
Paul, Brisbane, Australia


#3

PS, yes the props were counterrevolution and I did get the expected zero torque effect.

Also, @Pdwhite, should this thread be moved to the Builds section?

Paul


#4

Thanks, very interesting. You went vertical, I would have tried horizontal.

What engine and props did you use?


#5

I mainly went vertical because I felt if one motor failed it would be easier to deal with an off centre thrust in that configuration. Most of the parts were HobbyKing sourced. There’s a detailed build blog at

http://e-ppg.com/index.php/forum/share-your-eone-project/55-parapush-project

Cheers


#6

So did this guy: https://www.youtube.com/watch?v=0URUs-tDsv0&t=485s


#7

He since went to single prop in ver 2 - I was very disappointed in that !


#8

Here is a coaxial 2 or 4 prop counter-rotating idea by using back to back motors mounted on a bar (vertical or horizontal) behind the pilot:

(Notice the motor driven rear left wheel.)


#9

This guy looked at both side by side and stacking about 8 years ago. He flew on the side by side configuration.



#10

Thanks! This is wonderful, sharing and learning.

The power in the side-by side is impressive.

Looks like an engine PPG.

No cage. The props are set way back and it appear to be difficult to get caught in them.

If a 40" horizontal U bar was behind the pilot, it would be possible to use a centered pair of coaxial motors spinning 36" props.

2 motors is less complex than 4 and it may be possible to fly on one.

I can ‘see’ a trike


#11

Probably cruise on one but two for lift - but just barely, if I remember correctly he might have only did level flight with 2 motors as the bats were poor. His one prop setup ver2 is only 100lbs of thrust.


#12

Is 150 lb of thrust the magic number that will allow tandem flying with a proper wing?


#13

Lets keep the concept moving forward!


#14

Here is another 4 motor idea for a trike or a quad: Using the pumpkin quad concept as the starting point, mount the 4 motors on the rear frame in the OpenPPG square pattern. Plenty of room for batteries. I would place the ESC’s on the open frame for cooling.


#15

150 lbs. should be more than enough thrust for tandem flying. I’ve done tandems with a Top 80 motor creating only 105 lbs static thrust. You just have to have the right sized wing, a lighter (150-160 lb) passenger and an experienced pilot. Top 80 tandem flying is rare, and only usually done to demonstrate the motor’s effectiveness at its highest level. You’d need the Top 80 to be screaming at full power, and your climb rate would be poor requiring a large launching field, and no high objects around it. The usual minimum I would think you would need for tandems would be about 135 lbs thrust.


#16

I want to lift a trike and 50 pounds of batteries which should be less weight than a tandem. I weigh 175.

4 of these from eBay should do it:

"
(NOT BELIEVABLE)

New message from: eagle_technology (15Yellow Star)

Hi

if you want to the thrust up to 150 pounds of thrust at 48V
we recommend that you use the mad m8 KV180 motor, please see picture

the mad m8 KV180 motor use 22X10 inch prop, one unit of thrust about 37pounds

if you buy the motor, The factory request you to have a big order quantity,

what is your mini order qty?"

180 x 48 = 8,640 rpm

This is the result:

22

  • Prop Diameter. In inches.

8640

  • Engine Rpm. ( Max )

1

  • Engine Gear. Example. 2,58:1 set 2.58, with no gear use 1.

565
= Prop Tip Speed in Mph.

20

  • Outside Temp. in Celsius ( Normal is 20 Celsius. )

767
= The Speed of sound in Mph. Calculated using outside temp.

0.7366362451108214
= Prop Tip Speed in Mach. Maximum performance between 0.8-0.92 Mach.

A propeller does not work well just under and over Mach speed.
Just under Mach (0.92+) the propeller will vibrate, make excessive noise and will have poor efficiency .

I believe that a 24" would be better:

24

  • Prop Diameter. In inches.

8640

  • Engine Rpm. ( Max )

1

  • Engine Gear. Example. 2,58:1 set 2.58, with no gear use 1.

617
= Prop Tip Speed in Mph.

20

  • Outside Temp. in Celsius ( Normal is 20 Celsius. )

767
= The Speed of sound in Mph. Calculated using outside temp.

0.8044328552803129
= Prop Tip Speed in Mach. Maximum performance between 0.8-0.92 Mach.


New message from: eagle_technology (15Yellow Star)
Hello

ok, we can supply the 120 amp ESC. AND mad m8 96v motor

but, The factory requires you to order more than 50pcs orders per order.
do you agree?
If you agree that each order is greater than 50pcs, the factory will begin to customize your motor and ESC

waiting for your reply

Anyone interested?


#17

New message from: eagle_technology (15Yellow Star)
Hello

About you request for 96V 125 Amp ESC.
we understand that if the voltage of the ESC is higher, the price will increase exponentially.
therefore, The price you request for 96V 125 Amp ESC will very expensive

If you can reduce the voltage to 74v to 81.4v, this will reduce a lot of costs, The voltage reduced and will not affect motor thrust.

please let me know

Thanks

New message from: eagle_technology (15Yellow Star)
Hello

because the mad m10 motor can not sale in United States
so, the factory is developing the motor for you, it will take time, I will inform you when development and testing is completed.
please wait patiently


#18

https://alienpowersystem.com/shop/esc/alien-sport-ii-450a-4-24s-esc-hv/

Pretty impressive ESC!


#19

[https://alienpowersystem.com/shop/brushless-motors/20080-outrunner-bldc-motor-50kv-45kw-paramotor/]

For a single motor system.

“Specially developed for electric paramotor application. Silent, powerful, lightweight. This motor is capable of thrust up to 100Kg with a 42″ carbon prop. Powered by 24S 22000mah Lipo batteries.”


#20

I was seriously looking at doing the single prop diy system - decided that the folding prop was more cost effective in the long run as an esc or motor failure is cheaper to fix -and I wanted the folding to make my travels as compact as possible so I can take it with me on vacation.
Cheers, Patrick