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Member postings for RottenRow

Here is a list of all the postings RottenRow has made in our forums. Click on a thread name to jump to the thread.

Thread: Judder on all servos with DFT module
10/12/2019 23:01:10

I have been playing about with a few combinations of transmitters and FrSky receivers. It does look like the issue is something to do with the frame rate as you thought Phil. I didn't notice any difference between several FrSky receivers of different ages and versions.

With the DFT Module in the tx, and set to V8 mode, I measured the frame period (ie the gap between each successive pulse to the servos) at around 18ms with upto 0.5ms variation. Looking at the signal to the servo (on an oscilloscope) I could see the frame rate varying when no tx sticks were being moved. I tried this with both the two-way DFT module and the older non-telemetry type and results were similar. This is a frame rate of around 55 per second, but with variation of plus or minus 2.

I then set the module to D8 mode, rebound the same rx and the frame period was still 18ms but was solid with no variation. The servo operation was definitely smoother but the stepping was still there to a degree.

For reference I installed a 35MHz module into the same transmitter (9ZAP, still set to PPM mode) and measured the frame rate out of a suitable receiver - it was 22ms and very stable. The same was found with a 9C tx (FF9), and a FF7 had a frame rate of around 21ms (there are less pulses per frame as there are fewer channels). This is about 45 frames per second. This is being generated by the tx and in 35MHz PPM is what is received by the rx and then decoded and sent to each servo. Servo operation was, as expected, very smooth.

The FrSky module takes in this same signal from the tx. So it is getting around 45 frames per second from the tx but is sending them out (to the rx) at a faster rate. I guess what is happening with the FrSky module is that, in trying to send 55 frames per second, it will sometimes send the same frame twice (which will halt the servo for a moment) then the next frame will be correct again and the servo will respond with a step.

I have also tried a number of different models of servo and the effect is more pronounced on some types than others. Futaba 148s and S3003s seemed worse, a HiTec HS-311 was definitely smoother. Perhaps it is slower to react to input changes.

Finally I tried a FrSky Taranis tx with the V8R-II receiver set to 'D8' mode. The servo operation was smoother and nearly to 35MHz standard. The frame rate was 55 per second again and dead stable.

So I suspect that the main reason for the servo 'stepping' is the difference in frame rates between the transmitter itself, and the rate generated by the FrSky module. The faster rate to the servo (compared to 35MHz) may also be having a slight effect.

If I am correct in saying this, then using the module in D8 mode and perhaps choosing different servos is probably all you can do. Once in the air I doubt if the difference will be noticeable.

Sorry for the long post, I hope you are able to follow it....

Brian W.

10/12/2019 12:11:59

I have exactly the same symptoms with a later DFT module (the two-way one) and the VR8 receiver (more than one). In my case the transmitter is a Futaba 9ZAP and it's definitely set in PPM mode.

As Engine Doctor says, it is a kind of stepping rather than a judder, most noticeable if the sticks are moved slowly, and more noticeable by the sound made by the servos (mostly 148s in my case) than by actually looking at the control surface movement (though you can see it if you look carefully). It is also much more apparent on some models than on others, but I suspect that this is down to the accoustic properties of the different airframes and servo mountings. It's only really noticeable on one particular model, the others you have to listen specifically for it. You would not notice it on an ic powered model with the engine running.

I have just transferred the module to a different transmitter - an FF7 (the old type with mechanical trims) as a test, and the symptoms are still present. So it's not specific to my 9ZAP. Also putting the module into low power (range check) mode doesn't change anything.

I have flown the models like this for 100s of flights now and there appears to be no side effect whatsoever. Until I noticed this forum post appear I had thought nothing of it.

I have some of the original (non-telemetry) Futaba FrSky modules, and some receivers of varying vintages, so will set up some kind of test later and see if a pattern emerges. I will also try to connect the module to a non-computer transmitter to see if that's any different.

Incidentally, some time ago, there were a few occasions when on switching everything on I had no output from the receiver. This turned out to be one of the two DIP switches on the back of my tx module which had had poor contact integrity (several thousand ohms when closed) - this meant the module was firing up in the wrong mode. I soldered a bridge across the switch and have not had an issue since. I don't use telemetry mode.

Brian W.

Thread: BMFA News Dec 2019
09/12/2019 08:25:47
Posted by Gary Manuel on 08/12/2019 23:18:31:
Posted by RottenRow on 08/12/2019 21:55:54:

The latest BMFA News explains it all very clearly as well. The included exemptions will save each member having to print them at home, though the 400 ft exemption was not included for some reason, or not with my copy anyway.

The two new exemptions 1327 and 1331 state on them that a copy of the exemption along with a copy of the relevant documents must be carried by the remote pilot at the time of the flight. The older 400ft exemption does not state this.

Thanks for pointing this out Gary, I hadn't noticed that.

Brian W.

08/12/2019 21:55:54

I agree entirely with all of the positive comments above.

As far as I'm aware, the BMFA doesn't make anything out of collecting the £9.00 CAA fee, but if the member who it applies to pays their fee to the BMFA via credit card the BMFA is allowed to deduct the credit card fee, so only passes on the remainder to the CAA. £8.80 or something like that. That was as pointed out at the recent BMFA AGM, so the BMFA doesn't make a loss on the transaction.

Our club (Bedford and District) had its AGM last week and after the usual proceedings we helped a number of our members who were concerned about the test to take it on the night, online using a couple of PCs connected to the internet. Their fears were dispelled, all passed and all paid their £9.00 fee along with their BMFA and Club renewals. This evening I have renewed nearly 30 members on the BMFA portal and registered them at the same time. All worked well.

The latest BMFA News explains it all very clearly as well. The included exemptions will save each member having to print them at home, though the 400 ft exemption was not included for some reason, or not with my copy anyway.

So yes it's a definite thumbs up to Andy and the rest of those at the BMFA who have made everything as easy as it could be.

Brian W.

Thread: Ebay sellers...
13/11/2019 18:40:54
Posted by Daithi O Buitigh on 13/11/2019 13:44:41:

I think this one doesn't so much need 'some assembly' as much as last rites (but then again, it's on the US site)

I found most of the "models" advertised amusing but this one really had me laughing!!! The Mustang / Harvard or whatever it once was....

I love the seller's (well, the hopeful seller's) description and the sheer optimism that he must have had when he wrote it....

"Just needs some wood and glue" and "can't find the cockpit cover or the guy that was in there"; you can't read it, or look at some of the photos, without smiling.

I've just added it to my watch list... and see there are 11 others watching it too.

Brian.

Thread: YT 72" Hurricane
13/11/2019 17:53:33

Geoff, Andrew,

Thank you both for your responses. Thanks Andrew for scanning the instructions for me, they will be helpful.

I've still a few things to sort out on the model but when it's ready I will update the posting.

Brian.

11/11/2019 19:27:02

I picked up a YT Hurricane at this year's Nationals Bring and Buy, it's the older 72" version, with a Laser 150 fitted.

I am just in the process of sorting out various issues with the model.

I know it's a long shot but does anyone have a copy of the original instructions for this model please?

I am looking for initial control surface movements etc. As bought there is excessive movement on all of the control surfaces with the radio set to anywhere near 100% ATV. I can of course reduce this on the tx but would prefer to do most of it by lengthening the control horns where possible, or moving the pushrods inwards on the servo arms.

Thanks.

Brian.

Thread: silver solarfilm
23/10/2019 23:07:45

Andy,

I'm a bit confused here...

You say you are having the problem using silver Solarfilm, then in your last but one post go on to ask about fabric covering. You also say that you are covering a 1/4 scale Tiger Moth.

The fabric covering from the Solarfilm company is Solartex (or rather was..). Are you sure the product you are using is not Silver Solartex??

Silver Solartex definitely marks very easily, much more so than any of the other colours they made. It's got something to do with the silver finish that lays on the surface. Even with a proper sealing iron it will mark where you press down onto wing ribs, or any other part of the structure, unless you are very careful. Silver Solartex has a slight sheen to its surface but is not glossy.

Silver Solarfilm (the shiny stuff) has the silver colour in the adhesive (ie underneath the plastic film itself) and doesn't mark any more than any other colour in my experience.

Brian W.

Thread: The Warbirds Replicas Macchi C.202 is Landing!
07/09/2019 22:07:27

I would like to add that Brian's Macchi flew superbly at the Nationals and his final position in the results table really didn't do justice to his flights.

As well as flying the actual manoeuvres very well (both the mandatory and his chosen ones), the sections of flight between each of them was also flown in a very scale-like and smooth manner. This is, or should be, taken into account as part of the 'realism of flight' score.

If I didn't already have far too many models to build / finish I would be sorely tempted to build one myself!

Well done Brian for taking part and setting an example to those of us who keep thinking about entering the scale comps. but don't quite get around to it....

Brian W.

Thread: BMFA Website down...?
27/09/2018 08:07:54

Working here too, looks like you've done it Andy. Thanks.

Brian W.

20/09/2018 22:43:27

The site doesn't work for me either. I get the message below:

This page can’t be displayed

Turn on TLS 1.0, TLS 1.1, and TLS 1.2 in Advanced settings and try connecting to https://bmfa.org again. If this error persists, it is possible that this site uses an unsupported protocol or cipher suite such as RC4 (link for the details), which is not considered secure. Please contact your site administrator.

 
The TLS stuff is already turned on. PC is using Windows 7 and Internet Explorer 11.0.85 if that's of any use. There is no little padlock (usually to the right of the address bar) and to the left of the address in the bar there is a three-sided red and grey symbol...I thought the BMFA symbol usually appeared there though I may be wrong.
 
My iPhone (on WiFi) initially also failed to connect, giving a message about Safari being unable to get a secure connection, then suddenly it connected and has remained working for 10 minutes now.
 
Perhaps the above messages might provide some clue?
 
Brian W.
 
 
Thread: DB Sport And Scale - Cirrus Moth
11/11/2012 23:26:33

Martin,

What you have is the older version, made before the laser cut tailplane was supplied with the kit.

I had one for many years and still have the plans and the typed building instructions. Mine flew on the old type OS40 four stroke (pre-Surpass) which was adequate; that was later replaced by an FS40 Surpass which in my opinion was 'about right' for the model. A friend in my club has one built from the current version of the kit which is powered by a 52 four stroke. Almost too much power!

The plans don't give a lot of detail with regard to the ailerons, which are referred to as optional and were probably not a feature of the earliest models. The instructions state that if the ailerons are to be built, the lower wings are built first and the ailerons cut out afterwards. Ply plates are fitted for bellcranks to operate the ailerons from a single servo mounted in the centre section.

I can scan the relevant parts of the plan and the instructions and send them to you if you let me have your e-mail address.

Well done in saving the model!

Brian.

Thread: EDF Vampire T11
06/05/2012 15:22:52

Had a look at the DB version on their stand at Rougham yesterday, they had one that was half-built. Lots of laser cut parts, fuselage formers are much closer together than the model being discussed in this topic. It is built with pre-shaped packers under each former so that it can be built straight on the building board, the fuselage is planked with balsa strips about 3/8" wide. The wings are fairly conventional I think, with balsa skinning. The tail booms are built up much like the fuselage, formers and longerons then covered in balsa. The wings are permanently fixed to the fuselage but the tail booms (and tail assembly) can be removed by unbolting them from underneath the wings.

Should be available at the end of next month.

Brian.

04/05/2012 23:13:03

Hello Robin,

Thank you for the information regarding the retracts, they look a lot easier to use than mechanical or air units. Unfortunately HK are out of stock of the main units at the moment.

I am going to build the T11 variant and possibly the F5 short nose as well. I just need to draw out the T11 fuselage so that I can work out the former shapes etc. at the nose. On your model, is the fuselage as per plan from the cockpit back?

I see that DB Sport and Scale will soon be selling an EDF Vampire kit of similar size, apparently it needs a 90mm unit capable of 3kW to fly so I imagine it must be quite heavy. More information can be found here http://www.dbsportandscale.com/vampire.htm knowing their kits it will be of good quality.

Brian.

29/04/2012 10:14:31

Hi Robin,

I just came across your build blog whilst looking for something else...interesting as I am starting down a similar route using the same plan.

I previously built a couple of Tony Nijhuis' prop-driven Vampires, I modified them both but one in particular to resemble the T11 because I liked the shape of the fins. The colour scheme is as the one you are building. It shows up well against a blue sky.

I have since started on the EDF model from the same plan as you, though haven't begun the fuselage yet as I haven't worked out the redesign of the nose.

I am not going to use the foam construction method, rather I am going to cut the formers along the centre-line as you have done and build the fulage in two halves on the building board just like the old KeilKraft rubber powered kits. The fuselage will be planked in 1/8" balsa, then joined together rather like an easter egg.

Mine will be powered by a HET fan or something similar, I don't think power will be an issue as the construction will be quite light, although I shall incorporate the strengthening for the booms as you have. The original had to lift quite a few NiCads whereas modern LiPos will be lighter.

Which HK retracts did you buy?

I will continue to watch with interest.

Brian.

Thread: The June Grand Prize Draw
19/06/2008 13:26:00

Me too please!

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