LMA Genesis - Electric

[Andy Boylett]

My son Sam and me decided that since we are moving up to a half scale plane it would be a good testing ground for us to use an LMA Genesis. I have a 6KW motor (8hp) which is intended for a Vailly Aviation 98" FW190, but since this isn't even started yet we will use it in the Genesis.

We also want to try out the Turnigy high voltage 31kg.cm servos. HobbyKing are supplying these for our half scale plane and we want to try them out to see what they are like first.

Parts arrived from Belair this morning, in the snow (fastest I have ever got stuff from Belair). Fus is now together. Here are a few pics.

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Because this is a kit seen before I will tend to just show where mods for electric are made. Here is the first mod. The fuel tank floor now has a cut-out in the base. This is to give good access to motor mounting bolts on F1.

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Internal paper tube can be seen to carry servo wires from rear to receiver.

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And this is the tail end. I like to have an access door so that servo wiring and extension wires are easilly accessable. You can see the rear end of the paper tube through the access hole in the under side.

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[stuart cotgrove]

Hi Andy, electric is very tempting this time of the year.... Will watch with interest

What cells will you use, what duration would you expect and what speedo are you considering please

[Nick Reeves 3055]

i too am very interested in this one

[Andy Boylett]

Guys, Thanks for the interest. Myself and Sam have been using Turnigy kit for the last 2 years and find it great stuff.
I will be using a slightly smaller version of this Turnigy motor http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=5139 - they don't make the 6Kw one any more.....UPDATE - 6Kw motor now available again http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=5141

We use 5000mah 3 cell batteries in multiples of 1 to 4 ie 3 cell to 12 cell. The reason for this is that if any one cell fails then we have only lost a 3 cell pack and not a more exepnsive one The actual batteries we use are these http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=9183

In this model we will be using 8 of these batteries. This will be 12 cell so 4 packs in series, then doubled up with 2 lots of these in parallel to give 44.4v and 10,000mah. 6Kw at 12 cell is 135amps so each set of 4 packs should give approx 62.5 amps on full throttle. From experience we average less than half of the full throttle amps and since this is rather overpowered I would estimate an average current of probably less than 50 amps (25 amps for each set of packs). At 50 amps this is still 2kw average power useage. So at 25 amp average useage, this would give 12 mins to sells empty or 8 mins to 2/3 and lots in reserve.

As for esc, this is also Turnigy. This one which is 120amp continuous, 180 amp for 10 sec (if I can get Sam to stay off the power !!) http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=8921 or this one is we need to use full power for an extended time http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10332

Regards, Andy

[Andy Boylett]

Today's building:

Fus sheeting finished on the back. Added the thick balsa to the front top and then shaved/sanded half of it off again!

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Here is another of the hatches that is needed for an elec model. That hole is inside the canopy area and the canopy will be removable for battery access. The hole was reinforced before cutting. Below the hole is now a very solid base for the 8 batteries. It is 355mm long, which is more than 2.5 times the length of the batteries. This allows for 4 batteries abreast and 2 blocks of 4, with plenty of room for final siting of the packs later. I always do this as it allows me to balance the model using the batteries - so any final battery location lugs and holding down devices will be fitted after the model has been finished and covered.

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This picture shows another hatch. This hatch allows access to the motor mountings and the esc, which will be sat on the shelf with the holes in at the top there. I have put one 3 cell 5000mah pack in just to show how it can be easilly inserted through the canopy hole.

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That will be it for a while now as I am in hospital Wednesday morning for an op on my knee. I will probably try hopping to the garage as soon I feel well enough though!

[Andy Boylett]

OK, we are back to building the Genesis. Tail end now built and added....

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And the canopy has been completed in our usual electric style - we make hatches to be able to get at batteries whereever we finally decide to put them. I have used the little high power magnets for retaining the canopy - you can see the 4 of them in there (I started with 2 magnets, but with this size of canopy I wasn't happy with the force from 2 so added 2 more)....

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Wheels and unercarriage also done now. I find when I use the big plastic wheels that the hole can quickly wear with a large model and cause tracking problems on the ground. To combat this I fit a small piece of ultra thin stainless tube (nice tight fit in the plastic) so that the ss spins on the axel...

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[Andy Boylett]

Well, I have agreed to write about this build in the LMA journal, so no more on here for now. The journal report will show the completed plane and show the choice and instalation of the electrics for it - this will be a 6Kw (8hp) monster . Over the years I have been using electric I have developed a simple systematic approach to choosing and setting up any plane with electric power. I will share my approach with you and hopefully show that although electric can initially look complicated, by following this approach it takes the uncertainty out of choosing an electric set-up.
Regards, Andy

[Andy Boylett]

Hi,
This is now complete and ready to fly. Test flight will be in the next nice weather we get and hopefully a flying photo .

Can any of you that have flown one of these before remember what control throws you ended up with?

Cheers, Andy

[Andy Boylett]

We went out flying today and I tried to take some video footage of this plane, so here it is.................

http://www.youtube.com/watch?v=WmIG60NKAmY

.....I know my camera work is not quite as good as Sam's flying

[Dave Parry]

We went out flying today and I tried to take some video footage of this plane, so here it is.................

http://www.youtube.com/watch?v=WmIG60NKAmY

.....I know my camera work is not quite as good as Sam's flying

Hi Andy, glad to see you are back on your feet, now where is that article for the Journal?

[chris_bell]

8HP.....

Nicely over powered

Zenoah are only showing 4.3hp for the 62.... looks nice and frisky

Chris

[Mike Ellis]

How do you rig up TWO batteries and TWO on/off switches for 2.4 ghz using a spektrum 7000 reciever so i have a back up battery .??
Also i assume both batteries have to be charged seperatly.
There is only ONE battery input on the reciever and I am told you cannot just plug another battery into a spare input?
Electric and me just dont mix so I hope you can help !!

Mike Ellis

LMA 652

[Andy Boylett]

Hi Mike,
I make my own small units to solve that problem because nobody else does a simple unit. I have just been talking with HobbyKing and am trying to get them to produce one. It is very simple, just diodes. A diode will only let current flow in one direction. So, if each battery you use supplies its current through a diode then if one battery goes wrong it cannot discharge the other one.
I have put pictures below showing how I make my own units up....

Circuit diagram. The board is made from copper clad board sliced with a dremel attachment.


The reason it looks a little more complicated is beacuse I always use 2 diodes on each battery. I know this probably complete overkill, but I like having 2 of everything .

Here is the complete unit....








Regards, Andy

[Andy Boylett]

I forgot to add Mike....I use 2 cell LiPo's and run the whole plane at 8.4 volts (when fully charged). Because they are LiPo batteries I have them held in place with velcro and then remove them for charging where it can be done nice and safely in fire-proof bags.

We use the same LiPo batteries in all our planes from 1.5kg right up to this one. They are 1000mah, 20c, 2 cell Turnigy packs. They can deliver 20amps continuously if needed, so are able to cope easilly with the digital servos on full whack. With the Genesis we find that a 10 minute flight takes about 100mah out of each battery.

Cheers, Andy

[Mike Ellis]

HI Andy

Thanks for a masterclass in electronics lol I never use lipos as i just cannot understand them nor the charging of them at all, so I stick with metal hydride packs.
I will have to get a friend of mine to decipher your pics etc and see if he can make one for me ! as I still am little wiser as how to do it, inspite of the well documented pics you have kindly supplied, as my electronic understanding capability is NIL !
With the One diode fitted for each battery packs, ( fitting TWO seems even more complicated ! + what size diode is needed ??) and the TWO battery leads to the reciever, am I then able to use a spare reciever socket other than just the ONE battery output on the spektrum 7000 reciever ?
also are the two reciever on/off + charging switches, fitted to the aircraft as normal on/off swithes are ??
Being dead cheeky ! perhaps you could even make me one and i will pay you what you want?

God If i only had a brain !!!

Mike

[Simon Willey]

There is only ONE battery input on the reciever and I am told you cannot just plug another battery into a spare input?
Mike Ellis

LMA 652

Who ever told you that lives in fantasy land
You can supply power to the receiver on any channel. The pos and neg connections are on common rails on the 7000 rxs
So plug one input into the battery input and the second into any spare channel or if there is no spare channel "Y" lead it to any channel
You can buy a similar unite from SM services

Works on 5 cell packs . Just connect two fly leads to the rx connections to go into the RX



Simon

[Andy Boylett]

Hi Simon,
if you open up the SM services box you will find it has 2 diodes inside, connected just as I have shown in each battery lead. All the other electronics inside the SM Services box has nothing what so ever to do with protecting the batteries if one fails - that is the job of the diode. All the other electronics monitor the voltage leves and then switch the red/green LED's on accordingly. There are adjustable pots inside that allow to change the voltage settings for different packs.
Cheers, Andy

[Mike Ellis]

HI Andy,

As stated , a friend has looked at your pics that you kindly sent and he would like to know from you,

1: What rating ? are the diodes, and where can we get them from ?
2: Your diagram indicates TWO +VE IN and TWO -VE IN, but the unit picture indicates 4 soldering strips , so, could you make it a little clearer HOW
Positives and Negatives are connected, I would assume that THREE terminals are positives and ONE only, for ALL negatives?
3: As the positives & negatives OUT, are common,would it be practical to have just ONE reciever lead , and NOT TWO as shown, or do we have to
have the two leads for connection to TWO ports in the reciever.

4: How are the Batteries now charged? do they need to be disconnected and charged individually or is there another way of doing it.

5: It appears that BOTH batteries are online once the on/off switch or switches is activated , is this correct ??

regards

Mike

[Simon Willey]

Hi Simon,
if you open up the SM services box you will find it has 2 diodes inside, connected just as I have shown in each battery lead. All the other electronics inside the SM Services box has nothing what so ever to do with protecting the batteries if one fails - that is the job of the diode. All the other electronics monitor the voltage leves and then switch the red/green LED's on accordingly. There are adjustable pots inside that allow to change the voltage settings for different packs.
Cheers, Andy

And your point is ??
I said it was a similar unite to yours . It dose the same thing and would suit those who do not want to or do not have the ability to make one.

Simon

[Andy Boylett]

Hi Simon,
if you open up the SM services box you will find it has 2 diodes inside, connected just as I have shown in each battery lead. All the other electronics inside the SM Services box has nothing what so ever to do with protecting the batteries if one fails - that is the job of the diode. All the other electronics monitor the voltage leves and then switch the red/green LED's on accordingly. There are adjustable pots inside that allow to change the voltage settings for different packs.
Cheers, Andy

And your point is ??
I said it was a similar unite to yours . It dose the same thing and would suit those who do not want to or do not have the ability to make one.

Simon

Simon,
Just info for interest as if someone wanted to know they would likely have to destroy the SM unit to find out.....and since I have taken one apart already. More importantly the connections on the end of the SM Services unit are not great. I did speak with them to see if they did a version with either properly fitted connectors or solder terminals but they said no - because people want so many different fittings, hence the screw terminals!

Cheers, Andy