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Member postings for PatMc

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

Thread: What a sick world we live in
20/05/2019 21:30:01
Posted by kc on 20/05/2019 13:07:35:

It's banning caning in schools and now even smacking which has caused this general lack of respect for others. A little pain and lots of disgrace would help a lot to bring back 1950's standards at no cost.......

You mean Teddy boys intimidating people (and worse), fights between razor carrying gangs, cinemas refusing to show "Rock around the Clock" because of vandalism during performances...
In the the good old days of discipline instilling National Service.

There's been youths perpetrating mindless vandalism in every age even as far back as the ancient Egyptians.

Thread: SFM Piper cub.40 kit 67 ins wing span.
18/05/2019 21:28:56
Posted by Reno Racer on 18/05/2019 21:07:53:

Almost all tailwheel aircraft have their CoG behind the main wheels,

If they didn't they would rest on their nose when stationary. wink 2

Thread: Suggestions for vintage model
17/05/2019 17:18:46

A Veron Deacon would suit DC Sabre nicely, the PAW would be a good match for a Veron Robot if you liked to keep awake with a few aerobatics between bouts of gentle meandering.

Note both models have peg & screw wing fixing, the Robot has reduced dihedral & ailerons but will roll nicely on rudder alone.

OTOH a Sharkface or X-Kraft would keep you awake all the time with the AM10 [if it's one of the earlier pre-emasculated versions] as this one had before electrocution...

ga_top_before.jpg

and elevators were added.

dscn1463 (1280x960).jpg

Thread: IT help required please
15/05/2019 21:32:42

IMO Peter & Gary have probably nailed the problem. It's also easy to check on the Win10 laptop.
With the card inserted find it in File Explorer > right click on Removable Disk > left click on Properties & look at File System.
If the file system is either NTFS or exFAT do as Gary advised.

Thread: TE from top/bottom sheet
12/05/2019 21:05:10

Gary, the image is a snapshot from a pdf of the plan that I downloaded from Outerzone. The pdf file was made from a scan of an original KK 1955 Jnr60 plan.

Actually I did tidy the TE up a bit by overlaying with a layer from a cleaner section. You can tell by the 2 slightly misaligned ribs & where I didn't erase a blank part of the layer over "wing section".

Thread: Aileron differential
11/05/2019 23:32:56

I think you're right Gary.
I tend to only use differential on gliders at the same time use spoilerons. My main Tx's are FrSky using OpenTx. I don't use any "menu" differential setting but I increase the available aileron servos movement to max possible, offset the centres & adjust the outputs to my requirements.

Thread: TE from top/bottom sheet
11/05/2019 22:10:38

Here's a typical rib section copied from the OZ plan pdf.

jnr 60 rib.jpg The is rib clearly short of the extreme TE, which is glued then sanded. A generous bead of aliphatic when joining should suffice to fill the gap.
I'm pretty sure that's how mine was done when I built it around 1986 & it's still OK.

Thread: Wanted 2 BA compression screw (diesel)
11/05/2019 15:41:23

Donald, have you considered using a 2BA cap screw from Model Fixings ?
As well as being neater, using an Allan key is often more convenient & comfortable than the normal tommy bar.

Thread: Aileron differential
11/05/2019 15:30:06
Posted by Gary Manuel on 11/05/2019 13:25:47:

Reading with interest. I never realised the complication of coordinated turns.

Slightly off topic but I have a question that has always confused me. On my transmitter (JR DSX9) I have the option of using aileron differential in the main menu. I have a couple of models that require aileron differential; a notable one being a Hobbyking Lancaster. I can't remember the exact figures, but lets say it required 10mm up aileron and 5mm down. Rather than using the aileron differential menu, I simply reduced the travel (end point) of both aileron servos in the downward position. It appears to work OK.

My question is, is there a difference between using the aileron differential menu and simply using the travel adjustment to achieve "aileron differential"?

By using the end point travel restriction you're reducing servo power at the same time making the control coarser.

Thread: Down thrust?
09/05/2019 19:04:41
Posted by cymaz on 09/05/2019 17:31:09:

I built up the rear of the cabin to raise the wing trailing edge over 1/2”.

I left the engine thrust as it was.

That's effectively adding upthrust. wink 2

Thread: Zippy by Sean Bannister
09/05/2019 18:24:01
Posted by Nigel R on 09/05/2019 09:50:17:

I imagine Sean's glider experience probably used to good effect in the design.

I don't think Sean was seriously into glider comps when he designed the Zippy, I think at that time he had aspirations in the power aerobatic comp scene.

Here's a pic of him a little later when he was one of the top glider competitors - World F3B Champs at York 1987 (?).

Sean Bannister with Algebra 7 or 8

Subtle change in style by then. wink 2

Thread: Any ideas what this old model is please?
07/05/2019 20:44:00

It's a Super Tauri, plan No RC857 also at Outerzone.

On reflection it could be a Tauri from a Top Flite kit or an earlier RCM&E plan.

 

 

Edited By PatMc on 07/05/2019 21:03:45

Thread: Unknown Glider
05/05/2019 18:19:36

Pete, the Alpha 180 was one of many using that fuselage but it's fuselage had the same canopy cut away style as mine & it was only 1.8m span.
The actual canopies/hatches on mine are home made fibre glass replacements & have a slightly different shape to originals.

04/05/2019 18:52:28

Hi Stephen, I don't know what model it is but it looks like it has a generic plastic (plura ?) fuselage & tail unit that's held from below with a pair of 2mm nuts.
There were a number of models based on the same fuselage, tail & plastic interior fittings etc dating from just before brushless motors & lipos became popular. There was also some with a slightly different moulded fuselage, AFAIK the difference was in the canopy/hatch area only.
The models varied in wing span from about 1.4m upwards, until now the greatest span I've come across has been 2m. Most were rudder/elevator/motor but a few also had ailerons.
J.Perkins were distributors for some of them, most common being the 2m REM Easy Pigeon.
A Belgian company Protech also produced a number of different thermal & warm liner gliders using the same base parts.

I still have Protech Unlimited & a thermal model using a spare Unlimited fuselage & tail with an old 2m wing nailed on. Both have been converted to outrunner & lipo.

refurbed unlimited.jpg

The Unlimited after a recover job.

igor in red.jpg

Igor, made up from spare Unlimited fus, tail unit & old pair of glider wings. (Terry Pratchett fans will understand the name)

PS looking again at your model I'm guessing that the tailplane has been stretched a bit in order to maintain a reasonable tail/wing area ratio.

Edited By PatMc on 04/05/2019 19:05:54

Thread: Rx Voltage
03/05/2019 21:43:04
Posted by Nigel R on 03/05/2019 09:36:02:

pat, all due respect, I still do not see why you have said "acting like a linear reg". I don't think we can draw conclusion as to what exactly is wrong yet, all we know is that the output is low with no load, and swiftly goes south under very mild load.

 

DD, your SBEC should put out 5.5V with no load applied, you are seeing 4.9V, something is awry. Personally I would not be happy using the unit with an issue, but, your call, you are only planning on using the ESC function.

Nevertheless it would be worth seeing if a replacement was possible. You've paid for something that does two things and it seems unable to do one of them.

 

 

Nigel, the only conclusion I have drawn is that IMO the problem related in the OP matches the characteristics of a linear BEC as I described in my last post.
Not sure why you think only a mild load was being applied. I assume "waggling the sticks" means that all of the servos are operating back & forward simultaneously, which can cause as high or higher current peaks than would be normal in flight. Also if the motor was not running at the time the battery would have been at peak voltage, not a problem for a switching BEC but significant to a linear BEC.

Also the fact that there are instructions on how to wire up a UBEC, if required, in place of the built in BEC seems odd if the BEC is a switching mode type with the stated specs.

 

Edited By PatMc on 03/05/2019 21:46:13

02/05/2019 22:11:54

Sorry Chris, I misunderstood your post, I thought you were commenting on Dwain's reading of 4.9V when he was expecting 5.5v.

02/05/2019 21:49:07
Posted by Chris Bott - Moderator on 02/05/2019 17:19:57:

This could well be the SBEC dropping in volts but it could possibly be a connection somewhere that has a little resistance. Do you have any extension leads or switches or anything in line with the SBEC/Throttle channel cable?

It could be the connection between servo plug and Rx, or even the crimp between servo lead and it's plug.

Chris, as I read it Dwain got 4.9v when testing with no load (i.e. an open circuit) in which case a high resistance in line would have no effect.

02/05/2019 21:44:43
Posted by Nigel R on 01/05/2019 12:33:43:

Pat, what do you mean by this?

Both types of BEC should hold up the output voltage just fine.

Nigel, see me reply to Dwain.

02/05/2019 21:42:38
Posted by Dwain Dibley. on 30/04/2019 23:10:54:

Ok...........PatMc, you have lost me there a little bit, I am interested to understand what you are saying so please elaborate.

 

Dwain, a linear BEC uses a voltage regulator to reduce the input voltage to the desired output level but the total current drawn by the servos also passes through this regulator. This means that the difference in voltage between I/P & O/P times the current is dissipated in the regulator in heat.
For example let's say the I/P is 16.8v from 4s lipos with an O/P of 5v & 4 servos each drawing 1A . That's 11.8v * 4A = 47.2 Watts that has to be dissipated from the regulator. If the regulator isn't rated to this it will either burn out or shut down, either way power to the Rx is lost.
OTOH if there was only 3 servos the heat generated would be reduced to 35.4 Watts. If this is within the regulators rating all will be sweetness & light.

Further to this consider if the I/P was 12.6v from 3s lipos. That would give an I/P to O/P difference of 7.6v. With 4 servos at 1A each there would now be only 7.6v * 4A = 30.4 Watts to be dissipated.

Bottom line is that linear BECs are inefficient devices limited by a combination of the input voltage & number of servos they can run.

Switching BECs regulate the O/P voltage by switching the I/P on & off at a high rate with the the proportion of "on" to "off" time set to achieve the desired O/P voltage. They are very efficient (90% - 95%) so there's little heat generated in them & they hold a steady O/P voltage at full rated current demand over a much higher I/P voltage than linear BECs.
They are more complex & thus are costlier than linear BECs.

Sorry for the tardy reply, life got in the way of an earlier response.

PS there's a better explanation than mine of the difference between linear & switching BECs here.

Edited By PatMc on 02/05/2019 22:07:09

30/04/2019 21:41:37

IMO the BEC is behaving like a linear type rather than a switching type that the SBEC title suggests. Also, looking at the "How to wire up a UBEC" user instruction for this ESC makes me suspect that it could actually be a linear BEC.

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