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Member postings for Rob Ashley

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

Thread: Cheap Chinese Laser Cutter
29/12/2020 09:45:16

Probably best to use a cnc router to cut the foamboard. Either an end mill (0.6-0.8mm dia) or engraving bit (0.1-0.3mm dia).

Rob

Thread: Inverted Problem
20/10/2020 13:26:06

Tosh,

As you have a semi-symmetrical wing section, you will not have an equal amount of lift from upright to inverted flight for the same pitch attitude and speed. Therefore, you will need to increase the angle of attack (AoA) when flying inverted, generally by holding a little down elevator. Moving the CG will not remove this tendency completely, but may reduce the effects.

As you state that you currently have to hold in a 'reasonable amount of down' in when inverted, so you could move the long CG aft a little and retest using the upright dive method shown above, (don't use the inverted method as this really only works for symmetrical sections). I would recommend 5 mm at a time as you are fine tuning - but I will leave that to you.

Hope this helps

Rob

Thread: Ebay sellers...
23/09/2020 16:06:48

Fancy a

long term project?

Anyone?

Thread: JB Weld
21/09/2020 17:00:21

Ah, you may have exceeded the temp limits which might be why it fell apart.. I use the higher temperature version on my exhausts and all seems fine for me.

Strange we have had two polar opposite experiences.

21/09/2020 11:30:24

Did you heat the nut with a flame?

21/09/2020 10:56:54
Posted by Doc Marten on 21/09/2020 10:48:03:

I stopped using JB Weld not long ago. I was recommended to use it for a minor motorbike repair to the sensor magnet for the speedo, it fell apart. I tried again fairly recently for fixing a captive nut to the end of a ply engine mount, the nut came away. I was really disappointed by it.

Hi Doc,

Very interesting post. I built an aluminium exhaust system for a glow engine that is held together entirely with JB weld. It has held firm for about 7 yrs so far and is much quieter than the 'off the shelf' ones. I have recommended JB weld to others for such purposes, although I have not used in on wood at all.

21/09/2020 09:38:15

Talk about a timely post - thanks Cymaz.. I am just about start using JB weld to glue my 1/4 scale SE5a exhaust brackets together and was wondering the same thing...

I had considered soldering but holding all the parts together while trying to get the iron and solder in the right place seemed fraught with difficulties - now some JB weld and a heat gun to the rescue....

Thanks all

Rob

Thread: Airborne Battery Pack Duration
21/09/2020 09:34:54

Hello Tosh,

Must admit, I agree with you. The endurance of electric models is generally quite poor (this is also true of full size) - although there are some that have an endurance of over 10 mins and others may argue powered gliders much more. Most of my electric models have have flight times of 7 - 8 mins, which is a little short especially when you reach that time there is not much left for a go around if something / someone causes you to abort your approach.

I have an EDF F-14 that last 5 mins and no more on 2 x 6S 5000 mAh - another EDF model I have (a Hawk) lasts 7 mins if used very carefully on a 1 x 6S 5000 mAh, compare that to my longest IC flight of 42 mins they are in stark contrast. Granted most of my IC flights last about 12 mins, but 13-14 mins not uncommon if the circuit is active and I need to wait for an electric model to land before me. I actually find IC refreshing as I don't have to worry about throttle management or time as much, but still, most of my models are now electric.

Electric is a little more flexible than IC, in that a change of prop can mean the world of difference to the performance (either speed, thrust or endurance) setup of your model - much more so than IC. Alas, I don't think there is another huge step forward in battery tech for a while yet - although I could be wrong. Until then It really is worth spending time putting the correct prop on your motor as this will ultimately determine the amps you draw and therefore your flight time. I have often found the recommended prop from the manufacturer wasn't the one that fitted my setup the best.

Oddly I have more flights with my electric models (albeit shorter flights) as I don't want to take home charged Lipos - with IC that never seems to matter so I don't feel I 'have' to fly them. Odd really.

Rob

Thread: Cheap Chinese Laser Cutter
07/04/2020 09:16:06
Posted by adrian garnham on 19/02/2020 20:38:45:

Hi all

I have finished building a 5W laser cutter which is a hybrid between the FlyinFlynn and Geoff Gardiner machines (thanks to you both for your input as I don't think I would have been able to complete it without your help)

I am more than happy with the results for cutting balsa but not so impressed with ply so I have almost finished making a CNC router with a 500W spindle motor.

What type of cutter should I use for cutting up to 6 mm birch plywood ?

Adrian,

I have found that 1mm end mills, as shown by Geoff Gardiner, are perfect for cutting balsa and ply (you can also use larger). I found its is best in ply to cut no more than 3.2 mm each pass so 2 passes for 6mm ply. Balsa can be cut in 1 pass. Your total depth limit is the length of the cutter - so a 3mm bit with a 3mm shank can cut 20mm thick material.The main thing is not to stress the cutter and clearing the swarf is essential to reduce heat. I often use 0.8mm mills for balsa and even 0.3mm engraving bits for extra fine work.

Feed rate is also important so for ply I find 250 mm/min works well and 300-350m/min works great for balsa. You can go faster but I like to reduce the stress on the cutter - they last longer and you get a much better cut.

For aluminium and mild steel use decent end mills and I find 1,2 & 3mm proxxon bits are awesome.

Others may have their own methods/ideas that work - the info I have I found from personal experience and there is always something to learn. It is quite a fascinating part of the hobby for me and I have been CNC machining/routing for over 10 yrs now making everything from single parts to kits to engine parts. I hope you have fun with it as it can be quite absorbing.

Rob

Thread: NEW POLL - Has home isolation prompted you to start trad' building?
30/03/2020 14:15:45
Posted by Robin Colbourne on 30/03/2020 12:10:04:

I agree there should be another category:

"Got lots of projects that need repairing or finishing, but this extended lockdown has inspired me to start something new."

yeslaugh

In the same boat Robin

Thread: Vac Forming
16/03/2020 11:21:29

Hi David,

Vortex Vacforms, as Dickw mentioned, are the best I have found. They can mould from your plug. Give them a call they are very helpful.

Rob

Thread: Forum 2020 Mass Build discussion.
12/12/2019 16:05:12

Hi Piers - my delta was designed by my son and I.

12/12/2019 10:52:04

Perhaps not for everyone, but here is my Delta. 4S setup and goes like a rocket..

rob_delta-2.jpg

rob_delta-3.jpg

Thread: Rob's Grumpy Tigercub build
11/12/2019 13:51:26

Very smart - well done you. I like the starburst covering scheme too. So much so that I think that will be the type of scheme I use for my next own design.

11/12/2019 13:51:22

Very smart - well done you. I like the starburst covering scheme too. So much so that I think that will be the type of scheme I use for my next own design.

11/12/2019 13:41:35

Thank you Nigel.

Have you considered building one?

10/12/2019 15:50:46

Chris - Good for you! You wont regret it

Peter - That is very true! Recognizing single engine condition is the key to success and then flying accordingly. Although the mantra 'raising the dead' should be respected the GTC doesn't seem to mind turning in either direction with either motor out - just do it with care.

10/12/2019 11:41:44

Interestingly after some 25 flights I can confirm Peter's decree that she will fly well on one engine. She does indeed cope very well with asymmetric thrust after a problem I had during a take-off.

I initially setup both the throttles via a Y lead which worked well for a many flights, but then decided to give me trouble (in fact found to be broken). During take-off the right motor stuttered and then stopped completely a few seconds before rotation. So I continued the take-off and flew a few circuits one one motor. The compensating rudder input was quite linear with increasing power and so very predictable, so it was quite easy to fly a good approach and landing. She needed about 2/3rd throttle to fly in the cruise comfortably.

I did some more experimentation and found that you can take-off on one engine as long as you are careful during the throttle up - too fast and she will ground loop quite violently....even with full rudder deflection and tail wheel on the ground, quite exciting really.

I have since put each throttle into its own channel and, strange old thing, no more problems. But I must say this is a very capable aircraft with a wide CG range, good all round performance (even on one engine) and can be flown like a trainer or flick rolled to death across the sky - I think a great testament to the design.

Merry Christmas all.

Rob

Thread: Foam Wing Cutter
15/11/2019 09:04:54
Posted by Phil B on 15/11/2019 08:13:34:

I know a guy who uses metal guitar strings about 3 foot long, probably the top E string! He gets the right tension by tuning it! He can play status quo songs while it's warming up! 😜

laugh - Phil that made me laugh for ages.....

Thread: Centre of Gravity Machine
14/11/2019 15:21:28

Pete,

The Vanessa rig does work well but can be a bit fiddly with heavy models plus you need a strong hook to suspend the model from. It can also damage trailing edges if you are not careful with your positioning of the ropes.

For heavier models that you can't use your fingers for you could use some kitchen scales, a tape measure and a calculator (or an excel spreadsheet) - this is the most accurate way (to the nearest mm) and indeed the same method used on full size. It is very easy to do - if you are interested please PM me I can send you a document explaining how to.

Best

Rob

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