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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
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

Thread: Easter Eagle Senior
11/09/2019 17:44:47

You have made a very nice job of your Eagle there Anders!

Thread: Model vs Trees
19/07/2019 17:16:34

Certainly could be Martin... I still lead into a banked turn with rudder/yaw pedal due my flying career starting in gliders...

Best

Rob

19/07/2019 16:43:51

However, the seeming majority of pilots trained on lightweight foam models and taught to use glide approaches may disagree - at least until they move on to a higher wing loaded warbird and wonder why all the runway is behind them!

Edited By Martin Harris on 19/07/2019 16:19:3

Well said Martin - I guess the argument is then do you try to use the same techniques for all models or do you use 1 method for one (e.g. foamy sport) and a different technique for another (e.g. heavier warbird). For me in the interests of primacy (when things go wrong and panic sets in you revert to the first thing you are taught) I teach the one method..

There are many documents around that have arguements for both methods, although it is the accident rate that drove the recommendations to the method we now teach. Sadly most things in aviation take an accident to change things especially documents or techniques. I often quote to my compatriots/pupils that "the day you stop learning about flying is the day you should stop". Techniques, ideas and understanding evolve all the time especially in the flight test world, howeever it is your students who often 'teach' you a great deal about flying, especially when they get something wrong....laugh

I also agree with you that models react to power changes quicker than full-size due to inertia and as you say with foamies this isnt a realy problem but with higher wing loadings it really is...

19/07/2019 16:19:15

Hi Peter - that's very interesting and a good indicator of how we viewed engine reliability 50 years ago to the way we do now..... I think you are right and probably does explain the difference. It might also be where the cut and glide method transposed to model flying too.

I guess it's like most things - if it works is it wrong?

19/07/2019 16:00:40

Hello Martin, not really, it is applicable for all. Although I have seen both methods taught, in my experience the power for height method leads to a porpoising style approach and more heavy landings and is therefore not the preferred method. Interestingly, the use of power to adjust height has been a factor in a number of approach accidents and is not recommended. This is because that using power to adjust height takes much longer to see the height change than it will when using the elevator - given that the elevator is there to adjust pitch attitude the response is almost immediate - but as the speed slows then more power is required.

From my own experience flying full-sze for 30 odd years from light prop, through jets to helicopters, they all use the same technique. During my own flying instructional experience of 15 years ranging from ab-initio pupils to experimental test pilots we use the elevator (pitch) to control approach angle technique is used as it is a safer method.

For interest, if we consider an aircraft in its approach configuration (i.e. stable approach angle to the runway touchdown point and lined up on the centreline) maintaining the angle with elevator means that the pilot only has to alter the approach attitude into the landing attitude by a gentle flare then close the throttle to get touchdown - much less to do on the elevator.

Invariably the two controls (pitch and power) are intrinsically linked on the final approach.

Rob

19/07/2019 15:18:59
Posted by Peter Christy on 18/07/2019 12:28:41:

I was always taught to control speed with the elevator and height with the throttle. There may be exceptions during aerobatics, but it works very well in circuit flying!

--

Pete

Interesting Pete, In the full size word we teach that elevator controls the glidepath angle and throttle the speed. So on final approach we point the nose at the touchdown point from a given distance and height (thus giving the correct angle) and maintain that sight picture position with elevator and then keep your approach speed with throttle/thrust levers. I fly my model approaches like that too, although it is more difficult to judge airspeed of a model when it is flying toward you.

Rob

Thread: diy canopy
21/05/2019 11:03:05

Thanks for the links Andrew - most useful.

Up till now I have carved wooden plugs and hadn't thought about using pink foam, but i think pink foam it is for my next project canopy.

I was also considering making plaster of paris molds for some of my in-service canopies so if any damage occurs I can replicate another using the methods in the articles.

Rob

Thread: Lightweight Filler
07/04/2019 16:39:48

Big Boy lightweight filler is great too. It is a two part filler that sands really easily like p38 to a glass like finish - it's used for car body work and it is more durable than the one strike stuff.

Great for filling edges on removable parts like canopy hatches etc .

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