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  
Alan Pennington22/02/2017 20:32:44
avatar
174 forum posts
46 photos

Hi Mannyroad,

As everyone has said a job well done. When is the maiden flight?

Cheers Alan

Mannyroad22/02/2017 21:13:35
avatar
185 forum posts
81 photos

Thanks Alan,

Not quite sure yet. Weather's a bit unpredictable and I fly off the beach so have to get the tides right too.

I've a couple of other new builds I haven't flown yet, so must get down the beach soon.

If you build a Mirus, kepp me posted.

Alan Pennington22/02/2017 22:18:22
avatar
174 forum posts
46 photos

Will do Mannyroad. But not for a while, got to much to do on the house over here. Still trying to finish a model called the Pacer but to much is getting in the way.

Cheers for now Alan

David Foley23/02/2017 00:10:45
55 forum posts

Well done, wish I could build that fast. Colours look realy well.

Dave

Mannyroad12/03/2017 20:33:27
avatar
185 forum posts
81 photos

Hi guys,

Well, weather's been up to its usual tricks and, as I fly off the beach, this and the tides have to work with each other to be able to fly. So no maiden yet of the Mirus.

Anyway, to stave off boredom I've been busy re-drawing the plan of the fuselage for an electric version. its pretty much sorted now, based on using a particular HK motor. my problem is that I'm not very experienced with electric setups and though I've read back issues of the RCME to try and get a better handle on this subject I'd still very much appreciate the view of any of you guys who are big into electric.

The Mirus (i.c. version) has come in at 1600gms / 3.5lb all in, ready to fly. I gather that for a fast flying model I need around 200w per lb., so 700-750w should be about right, which is roughly equivalent to a 0.40 i.c I gather. Now, I want the electric version to go really fast, kind of like a pylon racer I guess, but I'm not sure if 200w / lb would give me this.

I have based the plan on a HK Aerodrive SK3 4240 - 740kv motor which runs on 4-5s lipo, has max. output of c.870w and max. current of 50A. My problem is that I'm not confident that I'm on the right track and I don't want to go and buy the motor and battery if its not going to give me the results I'm looking for. The same motor also comes in a 620 & 530kv version with slightly lower power and amp specs but I have made the assumption that I'll need the 740kv motor to get the prop spinning fast enough for fast flight.

I plan on using a 5s lipo to keep the amps down so I get a decent flight time. I already have a 60A & a 70A esc which i think will be ok.

As for the prop, I was expecting to be needing one of high pitch, like a 10 x 8. One review tested the motor, with the following results:

tested on brand new TGY 5S 3000mah 30C (fully charged):
1. 11x6 Cam Carbon (Aeronaut) 2780g Thrust, 38Amps, 770W
2. TGS e 11x10 2830g Thrust, 48Amps, 930W

Can anyone reassure me my thinking, setup-wise (motor esc,battery,prop), or suggest any alternative, before I buy the wrong gear?

 

Edited By Mannyroad on 12/03/2017 20:34:28

Edited By Mannyroad on 12/03/2017 20:37:08

Alan Pennington12/03/2017 21:45:23
avatar
174 forum posts
46 photos

Hi Manny,

Did you have to make much changes to the front end to covert it to electric?

Mannyroad12/03/2017 22:28:49
avatar
185 forum posts
81 photos

Only tweeks really. Kept the wing seating/retention the same.

Am hoping someone can help me with my electric setup query above. tweeked the plan for the HK Aerodrive motor and also did an option for the HK Donkey ST4010-820 too. But I need advice.

Anthony Pattison 113/03/2017 12:50:06
30 forum posts
7 photos

Hi Manny

Well the electric details you give all look very workable to me. The static thrust figures for the weight should be enough (!) and with a horse power (740W) on tap it will be fast that's for sure! From my experience with an OS32 on full chat (about 1hp) you will need a fair bit of downthrust so do make provision to adjust this if you can....

Tony

Mannyroad13/03/2017 19:28:40
avatar
185 forum posts
81 photos

Thanks for your comments Tony. Are you suggesting that maybe I'm over-cooking it?

By the way, yes, I've built in 2 degrees of down and right thrust and that works very well on my older Mirus.

Anthony Pattison 113/03/2017 19:55:49
30 forum posts
7 photos

Hi Manny

I don't think you are over-cooking it if you like very fast. Great thing about electric is you can easily adjust performance to suit what you want. With your setup I think you have bags of performance and by reducing cells or smaller prop you can reduce power if you want a bit less performance and longer duration... Post some pictures of new build? I now have 3 Mirus-us-us-es to sort but 1972 Triumph MOT tomorrow and still trying to sort workshop to take new lathe.... Not sure when planes come back to top of list!

Tony

Mannyroad13/03/2017 21:28:04
avatar
185 forum posts
81 photos

Excellent, I'll get the motor and batteries ordered up. Once I get going it won't take long but I've a couple of bikes too that need some attention for the Spring, and all the dreaded house jobs sad

Yep, will post a couple of pics but to be honest, apart from a lump of ally not sticking out of the front it won't look any different because I'm using the same livery scheme so i can just swap the wing over. Looking forward to trying the electric version though as I've not flown much electric stuff at all.

Alan Pennington17/04/2017 17:07:22
avatar
174 forum posts
46 photos

Hi Mannyroad,

Have you had the Mirus in the air yet?

Alan.

Mannyroad17/04/2017 19:02:53
avatar
185 forum posts
81 photos

Hi Alan,

 

No, not had much opportunity yet with hols and sorting out motorcycles for this season. Also, tides and weather haven't been pulling together for me to get down to the beach to maiden it. Might get a chance in two weeks when we are on neaps.  TBH I expect it to fly pretty much as well as the Mirus I already have and fly, but we shall see.

Finished the re-work of the fuselage plan for the electric conversion so am going to get cracking with an electric fus this week hopefully. If my calcs are right the battery will end up centred right at the CG point which is perfect. Will put a pic or two up on the forum when i've completed it, which might be just as the neaps arrive, so could have both versions ready to maiden.

Edited By Mannyroad on 17/04/2017 19:04:37

Alan Pennington17/04/2017 19:43:28
avatar
174 forum posts
46 photos

Hi Manny,

Do you race the bikes? Sounds good about the Mirus, photos will be good of the electric conversion and of the flying as well.

Cheers Alan.

Mannyroad17/04/2017 20:31:28
avatar
185 forum posts
81 photos

No, don't race them, just sports/leisure riding. Been building a custom bobber and that's consumed a fair amount of my time, but it's finiahed now, so have time to get back to flying/building stuff.

I'd love to video the flight of the Mirus but I'm not really well up on this stuff. I don't have a video camera and certainly nothing with enough zoom capability to show the Mirus in any other form than a dot in the sky. Will do my best though, when the time comes

Mannyroad18/05/2017 14:36:17
avatar
185 forum posts
81 photos

Hi Guys,

Well, been busy sorting out bikes and cars and stuff but eventually managed to find a bit of time to have a go at the electric version of the Mirus. I'm quite pleased with how it has come out, though i found myself making a number of changes to get it all sorted.

Below is the finished plane, alongside the fuselage of the IC Mirus I built in the blog. The wing is transferrable between fuselages, which might be good as it allows me to swap over to IC whilst the batteries for the electric version recharge. Well, thats the theory at least. Also put in a pic of my full squadron of mirus' too.

petrol & ic complete 2.jpg

mirus squadron.jpg

nose complete.jpg

batt hatch complete.jpg

I managed to get a couple of vents up front by the 'firewall' which means i'll get some good cooling air right alongside the motor body, hopefully. was intending not to have these as i thought they might look a bit naff sticking out of the side, but I thought the motor might get a bit warm, batting along on full chat. I was going to use one of those vented spinners but, from what I've read, evidence would suggest they have marginal if any real cooling ability. so vents it was. Stuck a tail vent in to allow the air out. Will let you know how it performs after testing.

Just need to check the CG now, before testing.  I calculated the battery position, offsetting for the loss of the IC engine, tank, throttle servo & RX battery, against the substitute gear (elctric motor, esc & battery).  The calcs placed the battery pretty much central to the desired CG so that will be beneficial should I opt for alternative battery makes, with different weights, as the battery is the chief factor in the calc, being 620g!!

If anyone wants any photos showing the main changes made, let me know and i'll post up pics. I was working from a revised version of the IC plan but found I still needed to tweek that here and there; will now update my plan to reflect the changes.

Setup as installed is the HK SK3 4240 740kv motor (which if I recall will give me 870watts on a 5s lipo), 60 amp HK Plush esc, 5s 5000mah Lipo. I'll see how it performs with a 10x6 APC-E prop up front (haven't put the watt meter on it yet to see what it draws static). Will say this though, I don't fly much electric, being an IC man, but boy when I nudged the stick to half throttle the plane nearly pulled my arm off! Am well impressed so far; reckon it'll be quick, though having the 5s 5000 battery is causing a weight gain I'd rather not have.

One thing I'd like to ask you electric buffs: I've read a few articles/threads on lipo discharging in flight and it seems I shouldn't discharge below 80% of battery capacity, i.e 4000mah. Is this correct? I've always believed that the esc's low voltage cut-off prevented over discharging, hence it cutting power to the motor before battery over-discharge. Is this not correct? If it is, them why do I need to worry if the esc will handle this aspect for me? As I say, I've not dabbled much into electric, the Cartoon Cutlass and my Gonzales being the only two electrics I've flown. help on this welcomed please.

Edited By Mannyroad on 18/05/2017 14:36:33

Edited By Mannyroad on 18/05/2017 14:46:47

Edited By Mannyroad on 18/05/2017 15:00:22

Jim Carss18/05/2017 15:03:25
avatar
1981 forum posts
42 photos

Very nice Mr. Manny,you will need your 20/20 vision to be on top form when that missile is in the air.

smile p

Alan Pennington18/05/2017 15:33:06
avatar
174 forum posts
46 photos

Hi Manny,

What is the weight differences? Looks great though.

Alan

Mannyroad18/05/2017 16:38:36
avatar
185 forum posts
81 photos

Hi Alan,

Just weighed it. It has come out at 2000g (4lb 6oz) dead, 400g more. The battery adds a lot of weight. Don't know enough about electric flight to know what capacity I can get away with for a 6-8 minute flight, especially given that you can only use 80% battery. The 5s 5000mah lipo is not far off 1.5lb!!

Some of the changes I made to the electric version added weight too, like adding 3mm ply for the fus bottom, with some small spruce strip around the battery hatch for strength during landings, given most of the bit that scrapes along the floor is hatch. Also there is a sizeable 3mm ply battery tray to carry the battery on bumpy landings, it being a brick.

Still, I was very surprised at the thrust it seems to generate, so it'll move fast enough to carry that extra weight; just wonder how fast its going to come in on landing. gulp.

Alan Pennington18/05/2017 16:47:36
avatar
174 forum posts
46 photos

Hi Manny,

Hope you get them flying soon.

Cheers Alan

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!

Find RCM&E! 

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
Overlander
electricwingman 2017
Wings & Wheels 2018
Expo Tools 14 July
CML
Gliders Distribution
Airtek Hobbies
Slec
Sarik
Advertise With Us
Latest "For Sale" Ads
What is the main brand of transmitter you use? (2018)
Q: What is the main brand of transmitter you use?

 FrSky
 Futaba
 Graupner
 HiTec
 Jeti
 JR
 Multiplex
 Spektrum
 Other

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us