Here is a list of all the postings David Germany has made in our forums. Click on a thread name to jump to the thread.
|Thread: Home Made CNC/Laser Cutter|
I have just finished my Dremel CNC from the Nikodem Bartnik design, I'm using Fusion 360 for CAD/CAM and Cncjs as the interface. Currently just messing around using a Dremel 3mm routing bit. Have you tried vinyl cutting yet, I've purchased a Chinese drag knife but need to make an adaptor to suit, I'm also interested in fitting a laser module and wondered what the capacity of these small units was in the real world, mainly in balsa and lite-ply / laser-ply.
Any info from anyone would be appreciated.
|Thread: Servo power-up movement|
Yes Martin, definitely selected 5 cell (6V) on the tester.
A good point though, would be an easy mistake to make.
Fully charged the battery then discharged at 2A as C8 suggests, after 80 minutes battery was down to 5.7V so looks OK. Will try the extended stick stirring with meter attached tomorrow. I'm more & more inclined to think this was a connector / wiring intermittent fault so will replace the switch / harness and connectors and bind connectors with floss to secure. I think we are also going to replace the Rx anyway.
Receiver was replaced after second crash, so unlikely to be the culprit. I'm thinking it's got to be along the battery / lead / connector / lead / switch / lead / Rx connection route. We checked the battery (2500 mAh 5 cell NIMH) after the crash with a load tester and it showed OK, and it still shows OK after 5 days so I don't think it's that but I will check for voltage drop with all servo's operating. I can't make the switch fail either even with lots of waggling.
As a matter of interest does anyone else get servo movements when switching on the Rx ? with the Tx on obviously.
It's the re-connection and subsequent servo twitching that ultimately caused the crash. On replicating the fault on the ground the ailerons would travel about 60% and the rudder about 20% in the opposite direction. You're right though about no servo movements when the power is cut, switching off the receiver and leaving it off the servo's do not move.
I was flying the model on the last occasion and it did feel as though something was wrong in the couple of seconds before the model flipped, my recollection was that the throttle was not responding, then the model rolled over and went into a dive, I then found I had control again, righted the model and cut the throttle hoping to glide back down.(it was only at about 15 / 20 feet at this point. Then the same thing happened but this time it just rolled into the ground.
Whilst investigating a series of crashes with a club members Wots-Wot (kit built) it seems the most likely cause was a momentary power interruption causing the servos to twitch on re-connection. Receiver and servo's have been replaced to no effect.
The cause of the interruption is most likely a faulty switch / harness or connection, and to this end we are replacing all wiring and connectors.
However this has got me to thinking why do some servos move temporarily on power-up, whilst some don't, and can anything be done to prevent this. It does not seem be brand specific, affecting Spektrum, Futaba, Hi-Tec and New-Power that I know of.
Obviously this is not normally an issue as we do not expect to switch the model off in flight but it would be interesting to know the explanation of why it happens.
|Thread: Bleriot XI|
I realise it's some time now since your Bleriot was on topic but I'm after a bit of info subsequent to crashing mine at the weekend. My error, let the airspeed drop too far on the landing approach in zero wind, dropped onto the runway from about 5 feet.
It's not as bad as it looks, the rear 'birdcage' has shattered and the front undercarriage support structure has broken away. All flying surfaces are undamaged.
As I no longer fly at an electric only site I'm thinking of rebuilding as IC powered. What was your final ballast weight with the SC30FS ? I have a Saito 45 Special which is 470g, and an RCV58CD which is 540g. My preference would be the RCV as it is compact and sounds a bit more scale than the Saito. It also runs great inverted. If these weights are less than your total up-front weight I should be OK.
Hope your Bleriot is still surviving,
|Thread: Mantua Models Kosmo 3|
Thanks for the links, I've finished the translation (2076 words), Using the instructions and the pictures on the build blogs it starts to make sense. Plus I've learnt some Italian. Noticed that the wings are built in a jig and include alternative ribs for fixed u/c or retracts, I have a set of 60 size electric retracts which I hope to fit.
Masher, no I couldn't find any online blogs, can you remember where they were ?. I had noticed the laminated leading and trailing edges and put this down to their laser cutter not being able to cut the full thickness.
Thanks for the replies,
I've found an on-line translator site that seems to work OK. As many of the words repeat it gets easier as you go, I'm about 2/3 of the way through (1014 words). I will try the email route as well though.
The first line of the instructions begins "Procurarsi un piano" apparently this does not mean "Get a piano", rather "get a building board" !!!
There are no full size plans for the fuselage, instead it is built in a jig using parts included in the kit.
Thanks again for the replies.
It's actually printed on the plan, but I estimate about 1500 words.
Have just purchased one of the above kits, it's a big box nicely packed and looks to be of good quality.
Problem is the instructions on the plan are all in Italian. I guess I could just build from the plan but I'm concerned that the quite lengthy instructions may contain some valuable tips which if ignored could prove embarrassing later on in the build.
Last resort will be to use an online translation site, but that could take some time.
Any help would be appreciated.
|Thread: Flair Fokker DVII downthrust|
Thanks for the ideas. I think I'll pack out the hard points with ply, fill the void with expanding foam and cut away the cheeks around the cabane fixing screws.
Finally the airframe and now need to fit the cabane struts / upper wing. I see that 2 of the struts fit through the plastic side cheeks which are glued on after covering. As these are hollow and fairly fragile I fail to see how this is achieved other than fitting hardwood blocks to fit inside the cheeks.
Any help appreciated.
Looking at a split fuselage for ease of transport / assembly. The images show my proposed method which is similar to my Puppeteer, just slightly beefed-up to allow for the increased vibration. Assembly involves connecting the two servo leads and inserting a screw from the underside of the fuselage. If the tounge joint is made with a close tapered fit then the lower assembly screw should tighten the assembly when screwed in.
Yes, the bearers are only dry-fitted at the moment, I need to get some more 1/2 x 5/8 beech to make some more, will try to get over to SLEC today to pick some up.I.m on the lookout for a used 70 but may have to save up for a new one.
Any thoughts on how to make the rigging easier at the field ? I built my Puppeteer with a split fuselage which makes assembly at the field a 2 minute job (2 servo plugs and 1 bolt) but that is electric and vibration free, not so sure about doing that on the DVII though.
Dennis, the plan notes do state 3mm liteply for that part, I think I'll laminate that and the front former with another layer for extra strength and gluing area.
I've reached this stage with the fuselage, although the engine bearers are not glued in yet. I've cut them to fit the Laser 80 so I'll need to make up another pair to fit the 70, or use a nylon mount as recommended by Jon. I'm not sure how I could fit the nylon mount now to give the correct thrust angles, I'd definitely have to reinforce the firewall as this is only 3mm liteply. Would staying with the beech bearers and reinforcing them with glass fibre/resin be ok ?
Ok, Feel happier about the thrust angles now. In the light of Jon's comments I think I will probably go with the Laser 70, luckily I havn't glued in the engine bearers yet which I had trimmed to fit the 80. (Jon, can you tell me what the current lead time is on a new 70 ?)
Thanks for the info.
Don, did you have any issues fitting the Laser 80 as that is what I am hoping to fit also. How did you arrange the exhaust ?
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