Topic: DB 1/4 scale Pup morphes into Fokker DVII

So after 211 flights and 41 hours flying in my ownership I might need a plan to help with a little remedial work.





Anyone got one they don't want or I can borrow?  

Alan

 

A sorry sight, but I'm glad you are in gonna fix her up PC .

Maybe we should have our own section on the forum for bi-plane repair

Two part fuz then for easy transportation

Two part fuz then for easy transportation

As noticed in a recent thread i am starting to get even more paranoid about these Pups.

In October 2007, I was standing next to Pat Cuss when his 1/3 Pup went in due to a shoot down. Then at Wings and Wheels I was standing next to Squarehead when his 1/3rd Pup went down in high winds. Then at Cosford I was standing next to CeeJay when his 1/3rd Pup suffered structural failure and plummetted to the tarmac.

OK, just ask who was standing next to PupCam when this happened... 

Some how Alan, I kind of feel responsible..  I am putting this all down to the Fokker scourge   

 

Two part fuz then for easy transportation

It's more than two pieces     Still, Solartex does make a convenient bag for keeping loose balsa in.  I've got another one as well that used to be a wing 

In October 2007, I was standing next to Pat Cuss when his 1/3 Pup went in due to a shoot down. Then at Wings and Wheels I was standing next to Squarehead when his 1/3rd Pup went down in high winds. Then at Cosford I was standing next to CeeJay when his 1/3rd Pup suffered structural failure and plummetted to the tarmac.

OK, just ask who was standing next to PupCam when this happened... 

Some how Alan, I kind of feel responsible..  I am putting this all down to the Fokker scourge   

Oh I can blame the sheepster then can I?

Anyway, gear on test at the moment - All flight gear working correctly (even the starboard aileron except that the gears are stripped), battery level is good and it's running on the FF9 servo test mode to see how long it keeps going.    Not really possible to do a range check though.

PupCam control system working fine, don't know about the camera and video Tx.  Its just that the airframe is totally bu**!*d 

Alan

Was sorry to see this yesterday Alan..

The pictures I was talking to you about don't show a lot but I will send them to you tonight when I get home from work.

P.S. I have a lovely shot of Mudflap's pup flying over the top of your downed aircraft if you wish for me to post it ?

Jeff

P.S. I have a lovely shot of Mudflap's pup flying over the top of your downed aircraft if you wish for me to post it ?

Yes, that's fine Jeff - just as long as it's clear that the Sheepster's Fokker didn't shoot it down

Oh no I've just remembered it didn't leave the ground (something about batteries?)

Alan

Yes, that's fine Jeff - just as long as it's clear that the Sheepster's Fokker didn't shoot it down

Oh no I've just remembered it didn't leave the ground (something about batteries?)

Alan

That's what I put on the "Mudflap's Pup thread" where he was trying to claim the kill....

Jeff 

That's what I put on the Tibenham thread where he was trying to claim the kill....

The Baa faced cheek of it

lol

Anyway, gear on test at the moment - All flight gear working correctly (even the starboard aileron except that the gears are stripped), battery level is good and it's running on the FF9 servo test mode to see how long it keeps going.    Not really possible to do a range check though.

2 hours continuous cycling with intermittent additional "aerodynamic" loading from me battery still on top green.   Tx down to 9.6V and test stopped.
I will try and do a range test although it will be engine off.

What caused it 

Alan

Now I've seen the pics its make it real :(

Was nice seeing that flying with the background of the sun setting at the field at the end of last year.

Perhaps that servo glitching you had a while ago never really went away and crept back in the form of something which took the RX out?

Our poor pups are having a bit of a bad time of it over the last couple of seasons. 
That's a lot of hours flying you have done with it.
Nightmare not knowing the cause of it. I hope you do find the answer .
Hope you get it together again. Like all the rest them it will be better for the rebuild but would have been even better if it did not happen.

Simon

Hope you get it together again.

If I do, I think it will be like Grandfather's best axe .........

If I do, I think it will be like Grandfather's best axe .........

I have a broom like that as well,think that was granddads 

Here you go Alan.....

Jeff

Mudflap looking for his downed buddy

I know what it looks like, but I was just doing a rekky for survivors, honest guv...

I know what it looks like, but I was just doing a rekky for survivors, honest guv...

Keeping those Fokkers away hopefully

Good photograph by the way Jeff

If you PM me your email Alan

I will send you the 2 previous pictures.

Jeff

Got a plan and re-built it.  
I think the plan wasn't very accurate 'cos it came out looking like this .......  





Not really, more like a bit of re-cycling.  Picked it up from Stuey today, it's the ex-Rugsley 1/4 scale DVII.    Slightly war-weary but it is essentially RTF just needs a bit of fettling.  Roll on the next Dwarf Patrol slot at Tibbenham, Osbournby or wherever
Engine runs well Stuey and so easy to start :colm:

Alan

Nice one Alan,

Have you cleaned it   

I noticed you buried the pilot! 

Have you cleaned it    

Yes

I noticed you buried the pilot! 

He's resting between engagements    Looks like the camera system would fit nicely

Alan

AWW PUP CAM,    only just seen this,    sorry about your pup,  i had great fun watching its pup cam antics last year,   you going to convert the DV11 for camera work??   Hmm  have to think up a name,    fokcam???   camfok

 Hmm  have to think up a name,    fokcam???   camfok

Doesn't quite work the same does it?    Mind you, better than Tripe Cam

Have you flown it yet Alan?  I know you have started her up and are pleased with the G38 

Have you flown it yet Alan?  I know you have started her up and are pleased with the G38 

think he's having glitchin problems...

Oh no  using the same receiver that went in with the Pup or a dogie ole sheepster one 

If it's the Pup one then it could explain it's demise 

Oh no  using the same receiver that went in with the Pup or a dogie ole sheepster one 

If it's the Pup one then it could explain it's demise 

No, I am 2.4, glitch free and all that, Pup's tried all sorts of rx and tx, but the elevator causes glitching, and he can measure the 4.8v nicad voltage dropping in tandem too.

I have suggested (well he suggested it first!) to change out the rx battery, but it appears to be bried deep in the cowl under the engine so may be an engine out job.

Oh, and the glitching goes if he run the rx of a separate battery to the servos...

The previous owner, Rugsley, ran it on 35m OK...

Certainly points toward the RX nicad then, perhaps it's not the nicad itself but it's situation being right under the engine/sparkie bit 

Certainly points toward the RX nicad then, perhaps it's not the nicad itself but it's situation being right under the engine/sparkie bit 

good point, but it's been alright up to now, and why only the elevator servo causing the glitching?

Oh, and I think it glitches with the engine not running.

Oh, and I think it glitches with the engine not running.

Shot my theory down in flames then ............. iffy servo?

Shot my theory down in flames then ............. iffy servo?

yes.... but works fine on 2.4g...

I would 1st unplug that offending servo to see if everything else was ok then swap a known working servo (elevator) into the problem channel, if thats ok then it's servo trouble.  Could be ok on 2.4 and not on 35meg if the servo is sensitive to poor signal or something and the 2.4 is giving a clearer signal 

I'm having a right old game trying to get the DVII glitch free.  To cut a long story very short I have found that when the larger  servos (Hiteks on elevator and rudder) are operating they induce interference back into the receiver which causes all of the receiver's decoder (ie channel) outputs to glitch.  Silly really as there are not long leads involved here (haven't really looked into the ailerons yet).  I've suspected Rx, Tx and servo problems but I've tried different Rxs (two types), Txs and Futaba 3010 servos and as many different combinations as I can and although sometimes I can convince my self it's OK, it never really is apart from .....     I know some will blame the Hiteks but others swear by them and I can get the same effect with the 3010s.   Also, I have not attempted to use the Rx that was in the Pup, that's hiding away in a darkend corner.

I've monitored the signals from the Rx with an oscilloscope and can induce the fault which can be clearly seen on the 'scope.   When waggling the sticks you can see the voltage level dip as the servos move and draw current and on occasion you can see the interference that effects all channels.  - Theory #1 High current draw from servos causes voltage as measured on output pulses from the Rx to drop which tends to suggest cabling from battery pack is not man enough.

Solution at the moment is to use the installed battery to power the servos and a seperate battery to power the receiver with the -ve line of both tied together as the reference.    This seems solid and I'm quite happy to go down this route and no glitching either on the servos or on the RX outputs can be induced. I've been tempted to chuck all the gear away including my 15 month old FF9 and go to 2.4 GHz - (crikey never thought I'd say that) but it's not really an option.     But as this means a bit of additional wiring I want to get to the battery and sort of do it from the ground up trouble is at the moment I can't see how to get the battery out.  I can see it I just can't get at it.   Stueys Suggestion #1 - Abandon the battery and add new one on C of G  Which is a good idea and gives me the chance to put some decent cable all the way from the battery to the Rx even if I don't go down the split supply route.

I've got a little video that show the interference as recorded by the scope if your interested.

<a href="http://www.youtube.com/watch?v=GtpjiVGdK6E" target="_blank">http://www.youtube.com/watch?v=GtpjiVGdK6E</a>

The display is actually monitoring channel 6 (but the same effect is seen on all channels) which is set to the mid position and hence the pulse width is 3 divisions = 1.5mS  As the elevator is moved up and down you can see the peak voltage move up and down (which I'm not overly keen on) as the current is drawn BUT every now and then you will notice the pulse width changes (it gets much narrower) which means the servo moves to the new "demanded" position briefly and thus the glitch.    Full range travel is represented by pulse widths between 1mS & 2mS.    Half way through the video the scope is re-configured to trigger on a pulse <1.2mS ish and you can see one comes along which is about 0.5mS and is thus the next glitch.   When I go down the split battery route the RX output never misses a beat.  

I hope that makes some kind of sense .........

I will report back when I've made some progress.

One things for sure - DVII stays on the ground until I'm convinced it's sorted.

Alan

Hi Alan

Did you by any chance try individual chokes (ferrite rings) on the servo leads?

Hi Alan

Did you by any chance try individual chokes (ferrite rings) on the servo leads?

I was gonna suggest that but after all the technical stuff (way over my head) that Alan has been through I thought I better shut up as my suggestions seem rather archaic by comparison 

Did you by any chance try individual chokes (ferrite rings) on the servo leads?

I've taken the servos and Rx (apart from the battery ) out so I can work on the bench and I've tried a ferrite ring (all I had to hand) on the active servo didn't seem to make much difference.    i.e. didn't appear to stop any noise back feeding from the servo to the Rx.

To be honest the effect is not so bad as it was (but still there) I can't see that removing it from the gear from the airframe will make much difference.   If anything it seems that the elevator servo seems to be the culprit as the fault moves with it as I move it to different channels.   At the moment, the reverse is not true i.e. the other Hitec and the 3010 do not seem to generate the problem.   Also noticed that the elevator servo was quite warm although that might just be that I had been cycling it nearly  continuously for 5-10 minutes      Now I've got the gear out I need to do a bit more of a methodical check - maybe tomorrow.

......... I thought I better shut up as my suggestions seem rather archaic by comparison 

Not at all Shaun, any advice gratefully received.   If I had some hair I could start pulling it out as I'm getting pretty hacked off with radio gear at the moment - I still haven't bottomed out the Pup problem yet.  All that was inconclusive

Alan

So Alan, has the D7 flown yet per chance?