Feb 17, 2011, 07:13 AM
Pat K
Mini-HowTo

# HP08 rewind simulator

Hi guys,
as promised you will find enclosed my excelsheet that allowed me to simulate my HP08 4 turns rewind performance before doing it. After having performed lift measurements on my scale, I have correlated the model which should be fully operational now. The spreadsheet is now fully automatic
Version 4.1 allows for wye connected motors simulation.

The way it works:
1/ don't make any change from Row1 to Row40: these are the calculation I made to elaborate the HP08 math model, based on real Don (Dbennettya) measurements with the stock HP08. You will find the motor efficiency graph on the right side that has been derived
2/ from row41 on, white cells must correspond to your setup. All the violet and green cells are automatic calculations. Don't change them
3/ if you get numerical errors, that means you've enterred now working parameters. To get out from these errors, just copy and paste a full working violet area (a complete bordered set of cells) onto the stuck one and put back your configuration setup.

Then the table gives you interesting data like:
- thrust
- power (electrical, mechanical, thermal)
- current at hover
- flight time (with your LiPo capacity)
- vertical acceleration (in g): put your model exact mass

You can also play with the maximum pitch to see the effect on thrust, HS and current.

Should you need any clarification or find any discrepancy, questions and comments are welcome.
Enjoy it.
Pat
HP08 simu-v4.1
Last edited by Papat; Feb 24, 2011 at 06:51 AM. Reason: New spreadsheet version V4.1
 Feb 17, 2011, 09:17 AM Pat K Thread OP One important thing I forgot to mention: I can easily create another sheet with any of your motors you would like to rewind in order to indicate you the optimum configuration power or flight time wise. The only data I need are the following: - HS at 0deg and 11deg pitch, 100% throttle, with at least 3 different pinion sizes (to solve the equations) - motor design: resistance, nb of turns, wire gauge, nb of wires, 1s or 2s Pat
 Feb 17, 2011, 10:20 AM Registered User Hi Pat, great research! and a formula to go with it. My electricity knowledge wouldn't fill a thimble...but from what I understand, the more winds= more torque and less rpm and vice-versa. Correct? regards, Bill
Feb 17, 2011, 10:59 AM
Pat K
Quote:
 Originally Posted by Air Vaca Hi Pat, great research! and a formula to go with it. My electricity knowledge wouldn't fill a thimble...but from what I understand, the more winds= more torque and less rpm and vice-versa. Correct? regards, Bill
Hi Bill,
the number of turns does change the kv (RPM) but has absolutely no effect on the maximum torque which is constant for a given motor design. A different winding only changes the Amp value at which the max torque is reached. And this is actually the trick: to get the max power of a given motor, you must use it at the max RPM the ESC can manage, then with the smaller pinion that permits to reach at the same time:
- the max HS/max torque at full pitch
- a RPM value close to the limit of the ESC: 60000RPM
Pat
Last edited by Papat; Feb 17, 2011 at 11:28 AM.
 Feb 17, 2011, 11:06 AM Registered User I just wanted to see your excelsheet, thank you for sharing. I have many questions I want to ask, but writing english is a lot of work for me. I'd like to see the simulation data of following setup. I'm looking for 2s setup to reduce current consumption to use battery more efficiently while keeping power as same as 1s hp08 11800kv + 16t setup. I'm cosidering 12 - 14 turns. Can you estimate the current value for hovering and sport flight and do you think 12 - 14 turns is a feasible solution for this purpose?
Feb 17, 2011, 11:40 AM
Pat K
Quote:
 Originally Posted by yosi I just wanted to see your excelsheet, thank you for sharing. I have many questions I want to ask, but writing english is a lot of work for me. I'd like to see the simulation data of following setup. I'm looking for 2s setup to reduce current consumption to use battery more efficiently while keeping power as same as 1s hp08 11800kv + 16t setup. I'm cosidering 12 - 14 turns. Can you estimate the current value for hovering and sport flight and do you think 12 - 14 turns is a feasible solution for this purpose?
Your objectives are not very clear to me. Are you just looking for longer flight times with same power as you have now? If this is only what you are looking for, I think going 2s will be a bit overdoing it. You will have to invest in new batteries, charger, ESC. Why not just optimising the motor you have and keep all the rest?
 Feb 20, 2011, 02:35 AM Pat K Thread OP New spreadsheet version uploaded in post#1. Enjoy it. Pat
 Feb 20, 2011, 07:58 AM Pat K Thread OP Sorry guys, now this is the good version. Wrong stock kv in the previous file. As an example, the first simulation shows the stock motor and allows to correlate Don's measurements. Pat
 Feb 20, 2011, 02:28 PM Registered User PapaT, Nice spreadsheet, but I've managed to break it If I change the pinion size to a too big size it errors and then changing it back to a ok size pinion doesn't fix it Would take me way longer to fix this so if you get time check it out. Putting in normal pinion size works great and if you go too big you can just not save the changes. Thanks, Don
Feb 20, 2011, 04:44 PM
Pat K
Quote:
 Originally Posted by dbennettya PapaT, Nice spreadsheet, but I've managed to break it If I change the pinion size to a too big size it errors and then changing it back to a ok size pinion doesn't fix it Would take me way longer to fix this so if you get time check it out. Putting in normal pinion size works great and if you go too big you can just not save the changes. Thanks, Don
Hi Don,
read the instructions in my post#1. When it bugs because of too large numbers, you will find the way to recover.
I've just made my new winding with 2 strands #30 4 turns. I got 280gr at 12deg pitch. Just crazy...
Pat
Feb 20, 2011, 06:27 PM
Registered User
Ok that is awesome what current, pinion and flight times?

How do we determine R1? is this winding resistance?

Thanks, Don

Quote:
 Originally Posted by Papat Hi Don, read the instructions in my post#1. When it bugs because of too large numbers, you will find the way to recover. I've just made my new winding with 2 strands #30 4 turns. I got 280gr at 12deg pitch. Just crazy... Pat
Feb 21, 2011, 03:19 AM
Pat K
Quote:
 Originally Posted by dbennettya Ok that is awesome what current, pinion and flight times? How do we determine R1? is this winding resistance? Thanks, Don
I've not measured the current. I'm only using the 12T pinion. I measured yesterday a flight time (in ST1) of 5:00 with my OS400mAh and 8:45 with the Hyperion 850mAh which are very consistent with the spreadsheet.
R1 is the resistance of everything but the motor (battery, wires, ESC, connectors). The value of 28mOhm is what I derived from your configuration thanks to your extensive HS measurement campaign.
Hyperion 850mAh have a lower internal resistance, this is why I consider 20mOhm in the spreadsheet with this battery.
Pat
 Feb 24, 2011, 06:52 AM Pat K Thread OP Version 4.1 loaded. Allows wye connected motors simulations. Pat
Feb 25, 2011, 09:12 PM
Registered User

# HP08S rewind

Hi all,

Just got finished rewinding an HP08S that I bought used. Four strands 32AWG 4 turns Delta with 12T pinion. Man this thing was a bugger to rewind especially since the winding window is packed so well you can't get any more copper in there. In fact during winding I had some turns pop off due to loosing tension but I was able to get them back on and tightened up Tested it on the bench without a pinion incase it didn't work right. It spins very fast and starts without cogging with no load. At very high throttle with no load I could hear the motor out running the esc so didn't do that too long. I green locktited the sleeve and pinion so have to wait until tomorrow to spin the blades up. Can't wait to fire it up

Can we mod the spreadsheet for 4 strands?

Don
 Feb 26, 2011, 05:02 PM Registered User Way to windy to fly outside so I did some testing inside with 8' ceiling so had to be careful but I can say a remarkable improvement Then I tied the heli skids down to a 1.5# book and ended up taping the book to my scale because it was rotating slowly on the scale I measured a max of 244 grams lifting force but it took a while for the scale to give a reading so I know it was higher but couldn't read it I think the battery OS 400mah 20C is being stressed during the static test due to a max 8A discharge so I didn't want to damage the lipo. The spreadsheet seems to be pretty close except for the battery limitation which is understandable. I then hovered and did light pitch pumps and flew around in the house for 4 minutes and had to put 311 mah back into the battery. So I will have to limit flight times to 4 minutes with the 12T pinion. The LiPo was 104.8*F and the esc FETs were 95*F so it looks ok. I may go down to an 11T pinion to see how the battery likes it. Before that I'll need to get in some outdoor flying to see the improvements. Thanks, Don