By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by CML

Mirus Build Blog

All Topics | Latest Posts

Search for:  in Thread Title in  
Mannyroad18/05/2017 16:54:43
avatar
184 forum posts
81 photos

Might have a go tomorrow, as tides don't cover the beach at the moment.

Anthony Pattison 118/05/2017 17:27:34
26 forum posts
7 photos

Hi Manny

I assume you mean you want to stop flying once you have used 80% of the capacity and stop when there is about 1Ah left in the battery? The ESC will stop once the batteries are near to ‘flat’ and voltage drops down to something like 3.9v per cell I would imagine. To stop at “20% left” you really need to do a few test flights of perhaps 4mins doing your normal flying and then look at how much energy is pumped back in by the charger. If you recharge and put 2500mAh back in after 4min flight you then know that 4mins of flight is about 50% of capacity so you should be OK for about 6 1/2mins.

Given you have a battery of 5Ah you could ‘hope’ for 50A discharge for about 1/10 Hr (6mins) and that would give you about 50A * 20V = 1000Watts. Hence the full battery capacity would give about a 1kW for 6 mins – you are looking for less power at 870W so that gives more time and you won’t be at full-chat all the time so 5 or 6 min flights should be pretty achievable for 80% discharge I would hope.

It would be interesting to see what figures you get from a current meter and rpm meter when running the prop you have. It is said that optimum prop would give (70% of kV*voltage rpm) so for your setup that would give 0.7*740*20 = 10,360 rpm…..

The nice thing about electric is you do have scope to adjust power/rpm/flightime by prop changing and battery changing – 1kW is pretty hectic for a Mirus but it will fly well!

Do keep us informed as I do need inspiration to tackle the 3 Mirus-es I have!

Tony

Mannyroad18/05/2017 18:03:46
avatar
184 forum posts
81 photos

Hi Tony,

Thanks for your comments, much appreciated. I wasn't aware about optimum prop sizing to achieve 70% kv; I always assumed one chose a prop that allowed the motor to achieve 100% kv rpm or thereabouts, so the info is useful. Thanks. Out of interest why 70%? I would have thought this suggests the prop is oversize and likely to over-draw on amps. not so clearly.

I've read some guys with the same motor are running 11 x 6 props and bigger so maybe my 10 x 6 will rev too quickly. Might need to source a 10 x 7 or 8 to 'push' the motor.

But yeas, will check it out with my watt meter and tacho and see what I get.

Mark Kettle 118/05/2017 21:51:41
avatar
1780 forum posts
1241 photos

I'd love to flying that Mirus, have fun Mannyroad.

Anthony Pattison 118/05/2017 22:28:40
26 forum posts
7 photos

Hi Manny

Not sure how scientific the 70% is but I think the kV figure is motor 'no load' speed so 70% gives some sort of efficient loading without bogging it down too much I imagine. Let us know what power figures you get and how early flights go. I hope to get back to models shortly but have just finished rebuilding a new (1963) lathe and have bought a new bike (1975 Trident T160) so need to clear out some stuff from garage before I can begin - better clear a couple of bikes and the old lathe for a start methinks!

Good luck.

Tony

Mannyroad19/05/2017 00:17:46
avatar
184 forum posts
81 photos

Mark, I will i'm sure, but gently gently at first methinks, hee hee.

Tony, had one of those Tridents back in 79. A Hyde conversion. Nice. Love the Trident.

Not flown my Mirus yet as I'm busy sorting out damage to my custom bobber (Indian Larry Grease Monkey replica), after dumping it down the road on a left hander last month (on a test run after taking over two years to build it!!). But I'll get both of them flown within the next two weeks and will update this thread with how it goes.

Anthony Pattison 119/05/2017 12:46:01
26 forum posts
7 photos

Hi Manny

Bike sounds very interesting, sorry to hear of mishap!

- perhaps you could photo the Mirus with a Bobber in the background next time!

Good luck with test flights.

Tony

Anthony Pattison 119/05/2017 13:01:50
26 forum posts
7 photos

Unfortunately someone moved the Mirus from in front of my bikes....

(sorry for off-topic pic!) Tony

20170514_120633 - copy.jpg

Mannyroad19/05/2017 13:53:31
avatar
184 forum posts
81 photos

Heeeey Tony, a nice stable of machines you have there. That trident takes me back. mine had same tank colours, best colours IMO.

Mannyroad19/05/2017 13:57:44
avatar
184 forum posts
81 photos

This is my build project before it slid down the road. Sorry, its blocking the shot of the Mirus, behind.

2015-05-09 17.34.16.jpg

Alan Pennington19/05/2017 14:35:49
avatar
171 forum posts
46 photos

Nice bike Manny, sorry about the accident after all the work you have done. What is the engine?

Mannyroad19/05/2017 18:59:11
avatar
184 forum posts
81 photos

Thanks Alan. Repairs are in progress and hopefully (if my mate pulls his finger out and gets on with repairing the tank) I should be back on the road in a few weeks. Sorting this out has stopped me finding some time to get the planes aloft; hopefully that will get back on track soon too.

The motor is an S&S 84" performance motor. Rare as hen's teeth.

All Topics | Latest Posts

Please login to post a reply.

Email News - Join our newsletter

Love Model Aircraft? Sign up to our emails for the latest news and special offers!

Latest Forum Posts
Support Our Partners
TJD Models
Overlander
CML
Skip Model April
Gliders Distribution
SHREK
Advertise With Us
How many plan-built models have you made or started in the last year?
Q: How many plan-built models have you made or started in the last year?

 0
 1
 2
 3
 4
 5
 5 to 10
 10+
 15+
 20+

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us