DSM Excelsior re-furb

[Jeffrey Cottrell 2]

14 minutes ago, Nigel R said:

Only thing I would steer by, simple tends to be reliable. Feed the servos and RC with a battery that needs no complex kit betwixt it and said devices.

Hi Nigel

Couldn't agree more, but sometimes life, or should it be LiFe gets in the way. Do wonder if sometimes I'm overthinking things. If I am, let me know.

Looking on Component Shop for some possible batteries. They have 5 cell, 2000 Eneloops, which are in the mix, but they quote maximum discharge current at 6a, unless you are using Futaba or JST connectors, when it's only 3a. Leads me to wonder if there's a limit to current if I'm using Futaba plugs.

I'm running 4 standard digital servos, three medium torque, one high, plus an HS81 on throttle and a Futaba S138G on retracts. What would be the current consumption with all those going at once. Must be getting close to 3a, should I be worried?

I replaced the switch as a matter of course, but it still connects to the receiver via a Futaba plug.

Not sure if that's going to be an issue.

Jeff

 

 

[Nigel R]

15 hours ago, Jeffrey Cottrell 2 said:

I'm running 4 standard digital servos, three medium torque, one high, plus an HS81 on throttle and a Futaba S138G on retracts. What would be the current consumption with all those going at once. Must be getting close to 3a, should I be worried?

 

Close to 3A, yes, no, maybe, depends on the aerodynamic load, possibly over 3A.

 

Easy answer, cater for 6A, (a) double up the futaba plugs (bit of a solder job) for 6A capacity, or (b) use 2 pin JST plugs. You might need to look at a widget to keep the the servo power connections away from the RX connector block, or get creative with some servo leads. I know what I would do, JST to the switch, then use two servo plugs, each one feeding power to half the digi servos.

 

Retract servo would ideally have its own pack, need only be small, AAA nimh or a 1000mAh LiFe. In case of bent legs etc.

[Peter Jenkins]

I have used standard Futaba and JR plugs on all my 2 mtr aircraft and so does everyone else that I fly with.  

 

My setups are for 5 digital servos plus the ESC.  A full FAI schedule takes 8 mins, has 17 manoeuvres plus take off and landing.  That consumes between 70 and 80 mAh from a 2S LiPo running through a Powerbox Digiswitch (regulated to 5.9 v).  The Digi switch V2 (can be set to 6 v/7.0 V/7.6 v/ unregulated.  See https://www.nexusmodels.co.uk/digiswitch-v2-electronic-switch-regulated-output-powerbox-6430.html.  The switch can be used with 5S NiMH, LiFePO4, LiPo or LiIon

 

So, I would just use standard servo leads and I would reccomend using the V2 Digiswitch as it is software controlled and if it fails it defaults to power on.

[Peter Jenkins]

On my current F3A model, I also use the Optipower Optiguard backup battery system that weighs 40 g.  See https://www.modelshopleeds.co.uk/catalog/product_info.php?products_id=30363&gclid=CjwKCAjwgISIBhBfEiwALE19SWJVFZJkW8ayI44274eVDLxVNmHw4s7CqljR3TCvqKFQ0r-X0V169RoCUI8QAvD_BwE

 

An option is to fit an LED indicator outside the model that can be seen when the model is flying to warn that the Rx battery has failed and the Optiguard has taken over.

[Jeffrey Cottrell 2]

Hi Nigel
Turning into a bit of a saga, this one, but I'm learning a lot. Really do appreciate all the help from you and Peter.
So, what I have so far. Bear in kind this was before Peter's latest post.
First, I'm going with LiFe for main power (sudden draught hit the dart as I threw it)
The one I've got coming is 2100Mah. Guessing this will give me enough for possibly two flights. Will check after one. If not, might opt for a bigger size.
That does leave the NiMh pack to power the retracts separately. Good thought of yours.
2500 4 cell is probably overkill, but I've got it, so why not?
Anyway, after the doubts about plug current, I started to look at the switch. (paranoid or what?)
 I replaced this as a matter of course, but the one I fitted was relatively small. The one I took out was a heavy duty item, physically pretty big and thick cables.
This was definitely overkill in its original form, with 3003's all round, but I think I could put it to use.
As always, not so simple.
The builder had managed to get glue all over the cables, so when I tried to separate them it tore the insulation. Got some new cable on the way, good for 11a, but since I have to re-wire the switch anyway, how about this:
Hard wire the battery to the switch input. It has a separate charge lead so all I would have to do is extend the balance cable. From the output side connect two servo leads so they can share the load. I'm using an 8 channel receiver so I have two unused plugs to connect these to.
So, good idea, bad idea or do I need some time in the 'funny farm'?
Your thoughts?
Peter
Your post came in while I was typing this. Did have a look at that Digiswitch. Not quite as expensive as the one I first looked at, but still £46. Bit too pricey for me.
Interested that an 8 min flight only consumes about 80Ma. Was a bit worried that the 2100 pack would not be enough, but then I realised I run my small electrics on 2200 packs and they give me 7 minutes with capacity to spare, at a much higher current than my servos will ever take.
So far, so good.
Waiting for some bits to come in, but plenty to keep me occupied in the meantime.
Work in progress
Jeff

[Nigel R]

I wouldn't hard wire. But otherwise sounds good.

 

A 2000mAh LiFe will be plenty for a whole day flying I would imagine. When I actually checked, I noted approx 80mAh drain per flight from a nimh on my 60 size glow.

[Jeffrey Cottrell 2]

Hi Nigel

Why not hard wire?

A wise man once told me 'simple tends to be reliable'. This would eliminate another connector.

Jeff

[Peter Jenkins]

I use a 2S LiPo of 850 mAh capacity in my 2 mtr bird.  I feel happy to fly 4 FAI(P) schedules before changing it.  Each flight is 8 mins total.  Weight, or lack of, is critical in aerobatics.  Why carry ballast around with you?

 

In my 2 mtr petrol, I use a 2,500 mAh 2S LiFe for the radio and another for the ignition system.  Good for 8 flights of 12 mins.  The tank is sized for 15 mins before it runs dry.  It did have a bigger tank but there was loads of fuel remaining after each flight.  It would probably have flown for 25 mins on that tank.

 

For aerobatic purposes, just flying around not practicing manoeuvres is a waste of your time.  You need to be clear what you are going to fly before you get airborne and then stick to the plan.

[Peter Jenkins]

I agree.  Never hard wire a battery to the switch.  Makes it more difficult should the pack misbehave.  A plug in connection, backed up with a servo lock device is fine as you are not plugging in and out all the time.  

[Nigel R]

As Peter says, you may need to remove it for routine maintenance at least, if not to swap packs on a long day or weekend at the field (can but dream)

[Jeffrey Cottrell 2]

Hi Nigel

Have to say, if removing the battery for whatever reason is necessary, then unsoldering a couple or wires is hardly a hardship. However, since both you and Peter suggest not hard wiring it, who am I to disagree?

Interesting conundrum as to what connectors to use.  The whole purpose of these ideas is to get rid of the dubious Futaba plugs, or at least give them an easier time, seems a step back to use them on the battery.

Had a dig through my goodies box (everyone should have a goodies box) and found some XT30 plugs. Again, overkill, but with a wrap of heatshrink, should be fit and forget.

I also can dream of a long day at the field, but if one ever comes along I'll have more that just the Excelsior with me. Don't think swapping packs will be needed.

Jeff

[Peter Jenkins]

Jeff, methinks you are worrying too much about connectors.  You are flying a 120 size aircraft.  The rest of the F3A world flying 2 mtr class aircraft uses standard plugs including World Champions. 

 

They used to go to great lengths to make 5,000 g although you are allowed 1% grace so 5,050 g!  Having a single set of + and - wires and 2 signal wires for the tailplane mounted servos was pretty standard.  These days many hit 4,850 g easily so can afford to fly with 5,800 mAh capacity flight packs.

 

KISS principle applies.

 

Peter

[Jeffrey Cottrell 2]

4 hours ago, Peter Jenkins said:

Jeff, methinks you are worrying too much about connectors.  You are flying a 120 size aircraft.  The rest of the F3A world flying 2 mtr class aircraft uses standard plugs including World Champions. 

 

 

Hi Peter

You could well be right, same thought had crossed my mind.

However, couple of things give me pause.

First, I'm a firm believer in Murphy's Law, waiting in the wings to catch out the unwary.

Second, I didn't build the model. It will be the biggest and most powerful in the fleet, and I'm depending on the builder knowing what he was doing.

Obviously I have replaced the servos, but also re-done all the control linkages so I'm confident in those, but nothing to say it's not going to fall apart from some other reason.

I know I've built in a healthy safety margin into the electronics, but that only means one less thing to worry about.

Also apart from the LiFe pack and hd wire, everything else came from my spares box. If I've got it, why not make use of it.

That's my thoughts anyway

Jeff

[Jeffrey Cottrell 2]

Hi Guys

Did say this would be an occasional series, didn't I.

So making progress on the Excelsior, but very slow. Seems like every time I finish something, I find two more that need attention.

Case in point.

Fitting the rudder and elevator servos. The old ones were held in by a selection of self tappers, all shapes and sizes. Fitted two ply mounting plates on top of the originals, to take new screws. Found a problem drilling the pilot holes. The wing is held on by those SLEC side brackets.

No problem with those except I can only guess the first builder fitted the servos before the brackets, so they got in the way of me drilling the pilot holes. Ever tried to find a 1.5mm long series drill late at night? Thought so.

Managed the job with my McGuyver hat on so they're now in and control runs rigged.

While rigging the closed loop wires, noticed the rudder had been fitted slightly too high and was fouling the fin extension. Managed to slice a thin strip of that to free things up, but made me wonder. In that state the rudder would never have centred, especially with the low power 3003's. Still not sure if the model had ever been flown. Things I found have made me think it probably has, but can't imagine it flew well.

Next up, retract servo. For some reason this was absolutely filthy. Seemed still to work ok, so pull it out, clean it and put it back in (yeah, right).

While pulling it out, noticed the pushrods to the retract units were only hanging on by a couple of threads. Ok, longer pushrods needed.

Couldn't find anything in my goodies box, so on to e-bay for some. Duly ordered.

Once the retracts were out, had a close look at the wheels. So old that the rubber had become hard, but also covered in what looked like Gorilla glue. Back to e-bay for some new ones.

See what I mean? What started as a simple clean the servo became a complete dismantle and refurb the retract system.

Don't get me wrong, still happy with the purchase especially as it only cost £90, which is about the value of the motor on its own. Also determined to get it in the air, but it's so frustrating, having to re-do so much, and wait for parts to turn up. Ho hum.

Patience is a virtue, so they tell me. At least given the weather, nothing much else to do.

Cheers

Jeff

 

[Peter Jenkins]

Keep going Jeff.  You'll be rewarded by a more reliable airframe.  Since you will want to fly the pants off it once you've got it airborne, reliability will be good to have!

 

Peter

[Jeffrey Cottrell 2]

Hi Peter, quick reply thanks.

Sorry if the previous post came off a bit like sour grapes. It wasn't really, just felt the need for a whinge.

Totally agree I'm trying to build in reliability as I go, also make things easily accessible for maintenance. However there is one thing above all on my mind.

After some of the things I have found, wondering if the plane, in its original form, was actually safe to fly. So many things either badly engineered or, like the retracts, holding on by a couple of threads.

I've said before but this will be the biggest and most powerful model in the fleet, and the thought of it getting loose in some way doesn't bear thinking about. Best case would be it makes a big hole in the ground. Worst case it makes a big hole in something more valuable.

So, I'm probably over thinking, and over engineering, some areas but it's all in a good cause.

The battle continues

Jeff

 

[Martin McIntosh]

Flicked through the last bits of this but I have a few thoughts on it. Forget NiMh`s, certainly not on only 4.8V, and I never trust in Lipos for a Rx pack since they are fussy and can be unreliable. LiFe every time now for me. Even an 1100 pack is twice what I had on Deacs in my competition days when I had to do up to five flights from a charge. A single 1800 is huge for an F3A model. I like to use 2x1100 via a Failover Switch (about £14, HK) which is exactly the same thing as a Powerbox one but neither are available at the moment. Regarding servos, an old style F3A such as yours does not require any powerful or particularly fast ones. Hitec 5485 or the equivalent Savox ones at under £20 are fine. You would need to be CPLR to tell the difference between those and some £200 ones.

[Jeffrey Cottrell 2]

Hi Guys

Bit of an odd question, but bear with me.

Working on the retracts on the Excelsior. Don't know which model they are, but they have the makers name OK on the units.

The axles are held to the legs by a bush with a couple of grub screws.

Trouble is the previous owner seems to have cut down the axles to match a pair of slim wheels. These wheels are knackered, but I can't match them.

So, first question.

Are the axles screwed into the bushes, or pressed in. If they're screwed in could I replace them with some HT bolts of the same thread, and effectively make new axles?

Other than that, anybody know of any wheels, 55mm or so, with very narrow hubs. Got a pair of these which I hoped would do, but the hub is 19mm wide, where I need 13mm at the most.

Any thoughts?

Jeff

[Peter Jenkins]

Have a look at these Jeff (https://www.bondaero.co.uk/Alloy_wheels/p1085152_20125201.aspx).  The frst two are 11 mm - I think.  Best to call Chris Bond as he might have some others as well.

 

Peter

[Jeffrey Cottrell 2]

Hi Peter

First with a reply, as usual.

Will have a word with Chris, see if he has any ideas, but tbh £15. Ouch

Jeff

[Peter Jenkins]

He's also got these but don't know the hub thickness https://www.bondaero.co.uk/Alloy_Flywheelz/p1085152_20898751.aspx  about £6.

[Jeffrey Cottrell 2]

Hi Guys

Changing the subject completely.

I understand there is an international cardboard shortage. Think I know why. My LiFe arrived today. This is the pack and the box it arrived in.

Enjoy

Jeff

[Nigel R]

Fairly sure you can get replacement axles for retract units. 

 

https://www.pegasusmodels.co.uk/product.asp?type=submenu&dept=5&maingp=Aircraft&prodid=1004779&offset=48#.YQo7i8nTWdM

 

Make sure you get the right size though. 

 

Or, bend a new pair of complete legs. The ok units just used 4mm wire, i think. 

 

[Jeffrey Cottrell 2]

Hi Guys

Nigel

Thanks for the link, great idea.

Bit concerned that they only list 30 size or 40 size. No-one seems to have any in stock, so can't tell me what size leg it fits, but I also wonder what size the axles are. Maybe that's why they specify a size.

Meanwhile, got a line on some wheels that may have a thin enough hub to use the original axles. Also spoke to Chris at Bondaero, who is going to measure the hub widths for the ones he has in stock and get back to me.

Work in progress.

Your suggestion of bending a new leg sounds good in theory, but I have no equipment to bend wire that thick. Also, I would need to make a good right angle bend at the bottom for the wheel. Can't imagine how that would be done, so I'm back to using axles.

Having said that, any idea how the legs are attached on OK units?

When retracted, one of the legs is not central in the housing, so the wheel fouls on the edge. If I could detach the leg, sure I could bend it just a little.

Now, some good service.

The wheels I am after are Perkins ones, generally cost about £4/pair. Loads of shops have them, but shipping costs more than the item, which I don't like paying.

Came across an unfamiliar company called B&H models. Website is in transition, so difficult to navigate but I phoned up and spoke to a guy called Alex. Not only were the wheels a little cheaper, but after I spoke about shipping, he said he would put them in a jiffy bag and send as a large letter.

Charged me £1.20, which I thought was very fair. Don't see old fashioned service like that too often these days.  Good on 'em.

Now, a question (not another!).

Plugged up the LiFe and put it on the charger, set to LiFe voltage. Charged happily for a while, then switched off with the message 'cell voltage error'. Did this a couple more times.

I have a cell checker which gives percentage charge. When I first checked the pack, it registered 2%. After switching of and restarting a couple of times, it now reads 45%. Still not fully charged.

Not that familiar with LiFe charging, so is this what I would expect?

Jeff

[Jeffrey Cottrell 2]

Further to previous

Set it charging again, switched off with the same message, but now a 63%. Again after a few minutes, but this time 78%. Looks like I will get to 100%, but in stages.

Odd that

Jeff