HC-Hobby B-25 Mitchell from Century UK

[Aidan]

 B-25 Mitchell from Century UK

 

Has anyone put one of these together yet ?

 

I rec'd mine and started to assemble however a typical Chinese gremiln has written the manual !

 

The build is quite straight forward however the electronics have left me stumpped.

 

I'm quite new to electric flight , and before I could even get to grips with all that that involves found myself in possesion of the Spektrum DX5e and AR500.

 

I'm sure this is adequate for this model ( sans flaps)

 

Anyway all the AR500 recivers channels are convieniently marked aile , gear , rudd ,elv etc - had no problem with other models

 

However the "Manual" refers to channels CH1 , CH3 , 5 & 6 - I have no idea what that represents on the reciver !

 

The wiring loom that now hangs out of the belly of the beast is messing with my head !!! - I cant trace back which is which ( expet the lights - 2 wires )

 

and as for the manual ... well it seems ot was part written for an A10 wrthog - refering to the ducted fans !.... as well as the retractable propeller ?? ( obviously meaning the retractable UC 

 

I would mail HC-Hobby however looking at their site tells me that a reply from the gremilin that wrote the manual is more than probable.

 

When this one done and dusted I think I contact them and ask for free upcomming models in return for re writing the manual to go with them !

 

BTW - nice looking model - hope when it's all finished it flys as goodl as it looks.

[David Ashby - Moderator]

Aidan,

 

channel 1 & 6 are usually ailerons

channel 3 should be throttle

channel 5 is likely to be the retracts

channel 2 elevator

channel 4 rudder

 

In truth you won't know until you plug 'em into the receiver but they're easily switched if not in the right place. Plug a little receiver pack into a spare channel if you'd prefer not to have the motors 'live' while you're fiddling about.

 

Sounds like you'll need to y-lead ailerons to channel 1 of course as you're using a 5-channel Rx.

[Aidan]

Thanks David,

 

All sorted now.

 

Works fine - all functions on a Spektrum DX5e transmitter and the basic AR500 rec. 

 

As you say above , exept that the ailerons are already conected to a Y and take up just the one slot leaving the spare aileron slot on the standard AR500 reciever supplied with a Spectrum DX5e for the lights. ( Anyone think that that could be a problem ? - seems ok on the bench )

 

I need only to make final adjustments and add the final touches and shes ready to go.

 

They should make it clear that this model will work as is from the box on the basic DX5e -  but without the option of doing a flaps upgrade.

 

Roll on the weekend - and the good weather.

 

Thanks

[Startazz No1]

Glad to see you have got it all sorted out now,i have been waiting to see this bird in the hobby shops so it's nice to see a couple of post up about her already,i first got hooked on this one while watching a youtube video of it,so how did you maiden flight go then Aidan ?

[Delta Whiskey]

Yeah how did it go Aidan?? Any pics too?

[steve moody]

Hello, I have been looking at this one to go with my expanding fleet and just wondered if the wings can come off for ease of transport or if you fix/glue them in? Steve

[David Lusty]

Hi Steve. You have to glue them. Or gelatinize as the instructions would have it. The wiring which others have referred to would be a nightmare to connect / disconnect on each visit to the field, anyway. The assembled model is a bit on the large side to fit in the boot, so you need a fairly big one. I have almost completed construction but haven't had a chance to test fly it yet.

[David Lusty]

Has anyone got any information about the BEC? Presumably one or both of the ESCs has a BEC. The manual says nothing about it. I would prefer to use a separate receiver pack, and have fitted it in the removable canopy which puts the CG in a good place but I'm not sure how I can disable the BEC as I don't know where it is connected. Maybe if I disconnect the throttle (Ch 3) power wire from the receiver plug?

[Tim Mackey]

No - if you disconnect that one, you will have no throttle. Remove the red wire from both of the esc leads and tape back, then use your separate battery into the main battery socket of your receiver.

With hindsight, I think this may have been what you were suggesting anyway - it just read as though you were going to remove the throttle pin ( signal )

Edited By Tim Mackey - Administrator on 27/11/2010 15:01:22

[David Lusty]

Thanks Tim. I think I probably would have taken out the correct one but it is reassuring to have your clarification.

[Craig Kane]

After a year of it sitting in the box, I've finally got round to assembling my B-25 and I'm having a bit of an issue wth the undercarriage servos. Everything works as it should but the servos are straining after completing the cycle (both up and down) and I'm concerned that I'm going to wreck the servos.

Is this actually a problem (or am I just stressing over nothing)?

Can this be adjusted mechanically or can I do it via my Tx? (DX6i)

Thanks

[Carl Muff]

have you tried you tube they is always some doing a guide for a model

[Pete B]

No knowledge of the model, Craig, but a quick look at a vid on Youtube seemed to show a maingear servo with over-extended travel which is, mechanically, pretty awful to watch......

I assume you have all 3 servos on the gear channel? If so, you could reduce the servo travel in the menu to a point where all 3 u/c gears lock down and lock up without over-straining any of them.

Try that and see what happens.,,..

Pete

[Craig Kane]

Thanks for the advice. I was thinking that it must be adjustable but I wasn't quite sure how to do it. I take it that I just go into the settings for the gear channel and reduce the throws until it stops straining?

I have to admit I'm very impressed with the model. The actual sequencing of the u/c is really well controlled. Only niggles so far have been a slightly ajar nose door (adjusted by moving the clevis) and poor rudder throws if going by the instructions. Mind you, having "gelatinised" everything and checked out the retractable propellers, I was expecting a few litlle quirks.

Really looking forward to flying this one, just as soon as the wind dies down!

[Pete B]

That's it, Craig. Adjust list, Travel Adj then alter the Gear figure with the Gear switch in your preferred 'off' position until there's no straining or servo noise, then throw the Gear switch to adjust the other end of the travel.

Make sure all three sets of gear lock up and down with the setting you select

Pete

[Craig Kane]

Thanks Pete. I'll try that out tomorrow and let you know how I got on

[Craig Kane]

Pete, apologies for the delay in replying, your advice worked. Found that the nosewheel retract servo is straining a little but I managed to back it off with reduced throws.

 

The maiden flight went without a hitch. Flew beautifully with the following setups:

On full rates: +60% expo on aileron & elevator

Rates: Aileron: 50% with +50% expo

Elevator: 60% with +50% expo

 

I increased the rudder to 125% travel as the throw was a little small even after adjusting the position of the clevises on the rudder, although I didn't use much rudder in flight, it gave a little bit more control over taxiing.

 

The only issue I have with the aircraft is that those HUGE u/c doors really do have an effect on the handling whilst on approach. I found myself having to use about 30% throttle on finals to counteract the drag. Even in a very light wind, they were doing a good job as airbrakes!

Edited By Craig Kane on 13/06/2013 10:49:01

[Pete B]

That's great news, Craig and thanks for letting us know.

All too often we hear of niggling issues with ARTF's and a bit of thought and application normally solves the problem, so it's good to hear she flies well.

In-flight shots or video next, then?.....

Pete

[Craig Kane]

I'll try to get some photos next time 

 

 

For the benefit of others I'd just like to add a few things that I encountered during the build.

Motors: The instructions don't tell you to reverse one of the motors. Even with handed props fitted, I initially found the model to be doing spot-turns on the ground. I forget which motor it was now as I just changed it round at the time. (left hand I'm sure)

Wiring: It's all a bit fiddly to get through the recess in the wing root and then through the fuselage. I wound a piece of thin wire around each one and pulled them through individually.

The extension & y leads for the servos are a bit of a nightmare. The connections simply push together and didn't look like they would remain secure so and taped up each connection.

The identification of the channels isn't the most helpful.

After much testing I set them up on my 7ch rx as follows:

Ch1: Ailerons (reverse)

Ch2: Elevator (reverse)

Ch3: Throttle

Ch4: Rudder / NWS

Ch5: U/C

Ch6: ---

Ch7: Nav Lights

 

Other than those little niggles, the overall build was straightforward. As said previously, the model flew on rails with no nasty tendencies, and flying at max chat on full rates was impressive. Very agile for a scale model and it is VERY quick.

Edited By Craig Kane on 13/06/2013 16:33:02

Edited By Craig Kane on 13/06/2013 16:40:06

[Olly P]

No throttle?

[Craig Kane]

Thanks Olly.

Post now corrected.

[sharpy1071]

hi Craig I think you'll find it is the propellers windmilling at zero throttle that cause the drag. I've flown mine now for three years and found out the hard way I always land with some throttle so that they just bite the air so as not to cause drag. I did try brake on the set up but it wouldn't work any better. My front centre door has been missing for a year or so and it makes no difference except in looks when retracted, hope this helps

[Craig Kane]

Just another quick update on this model.

 

After a somewhat less than textbook landing, I needed to replace the props. Century were unable to provide an exact replacement as the B-25 is discontinued, so they sent a pair from their (also discontinued) DH Mosquito.

They are the same size but with more pitch and the hole for the shaft is smaller so needs drilling out.

 

Checking the power output with the new setup produced some interesting results.

Motors and ESC's are as supplied and all powered by a Kypom 3s 2200.

 

Original setup: 300W, 35A at max throttle, 30A constant.

New setup: 575W, 60A max, 52A constant

 

Obviously far too much for the 40A esc's to handle, so after much fiddling with the settings on my DX6i, (throttle throw down to 50% and sub trim to -50) I managed to get it down to a more sensible ()  465W, 52A max, 40A constant.

 

That's the output at full throttle and to be fair, apart from take-off, I've never found the need to go above 60% in normal flight. It's quite entertaining though watching this big scale warbird keep pace with the EDF's at the club.

Edited By Craig Kane on 17/08/2013 17:05:33

[Craig Kane]

Having managed to break a prop blade on the take-off run on Sunday, I am unable to get a replacement from anywhere. I am thinking of going down to 2-bladed props in order to make replacement a bit easier.

Can anyone recommend an alternative prop set-up for this model? Currently using 10x7x3 counter-rotating

[Pete B]

10x8 should be a good substitute for the 10x7x3, Craig - just add an inch to either the diameter or the pitch to go to 2-blade. Keeping to 10" will be better for ground clearance if that's critical.

I see Robotbirds have GWS 10x6x3 in both rotations if they fit and you could manage with the reduced thrust.

You should be able to find 10x8 in normal and pusher somewhere - a bit of browsing may turn some up.....

Pete