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Old Dec 24, 2012, 01:21 PM
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Ken,
One thing i have done that has worked well in situations where the prop shaft treads dont stick past the prop hub enough, is make an extended shaft prop nut.

What i mean, is the prop nut has a smooth outer diameter shank (that is threaded inside to screw onto the prop shaft. The smooth shank penetrates into the prop hub (the prop hub has go be drilled to accept the size of the smooth shank). This allows you to get a proper tread qty. into the prop nut and keep the prop centered on the shaft. You can also keep the hex nut end solid and drill and tap that for a spinner bolt.

Ill see if i can find the setup i use on my seidel radial
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Old Dec 24, 2012, 01:23 PM
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Found it!
In the baggy above the prop blades:
Bottom right corner is the prop nut. The smooth shank goes into the prop hub and is threaded on its inside diameter. The acorn'd end is drilled and tapped for the spinner bolt.

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Old Dec 27, 2012, 07:47 AM
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Hope everyone had a great Christmas

Thanks for the ideas regarding prop adapters I am sure now I can come up with something.

Canopy is complete for now, carefully seperated the windscreen and glued in place. I wanted a method of holding the sliding canopy closed in place without using screws so came up with using the very large rear view mirror with a piece of M2 studding in the base, as its a piece of alloy the mirror actually works

Next up is to glue the motor mounts in place and wire them up
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Old Dec 27, 2012, 08:15 AM
Failure is not an option
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Elec motor / Radio set up

Ken - interested to see what you are using for motor/radio set up. Are you using sep batts for the radio vs taking power from the motor batts to power the radio? Interested to see the gizmos you have planned.
Rob
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Old Dec 27, 2012, 12:41 PM
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Hi Rob, I am using a seperate RX battery up in the nose to get as much weight forward as I can,

I have used 14swg wire back to a small distribution board made out of Vero, I will power Aileron and Flap servos seperately from this
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Old Dec 27, 2012, 01:03 PM
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Rx System

My interest in this was also for my 80 in Sparviero - after looking into using lipos I determined that I would have to step the volts down to avoid frying my servos (7.4 to 6v). This would require the equivalent of (2) BEC's, more connections, etc etc. I am planning on using the JR AR9100 which handles (2) input batts (ea backs up ea other) of just about any voltage, but it does not step the voltage down. What's wrong with that picture? So, I reluctantly decided on (2) 1000 mAh nicad 6V packs that I will probably stuff in the wing roots.

Noticed that you are using a mechanical valve for your retracts... have you seen one of these things? I am using something similar in my small Mossie and they are slick....

http://www.flyeaglejet.com/en/Electronic.html
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Old Dec 27, 2012, 02:13 PM
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Wow, only 2000 mah for an 80" airplane! I use more than that on airplanes 2/3 of that size!

Nimh/nicad technology is really old. Look into the A123 packs. 6.6v output, so no voltage regulators are needed
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Old Dec 27, 2012, 02:41 PM
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Quote:
Originally Posted by invertmast View Post
Wow, only 2000 mah for an 80" airplane! I use more than that on airplanes 2/3 of that size!

Nimh/nicad technology is really old. Look into the A123 packs. 6.6v output, so no voltage regulators are needed
I looked at them but since I am running 6v servos, won't still need to step all this down? Re the mAh capacity, I will be running (9) servos (2) of which are tiny for torpedo and light housing retract, (1) for retract switching unit (not really a servo), and then (2) ea for ail/flaps, elev and rud. This is not a particularly fast model with large control surfaces and the elev is aerodynamically balanced. 10-12 lbs is contemplated. Comments?
Rob
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Old Dec 27, 2012, 04:44 PM
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Rob,
A 5cell nicad can hit 7-7.2 volta when fresh off the charger. A 2 cell A123 rarely if ever goes over 6.9volts off the charger and quickly drops to 6.6-6.7 volts for nearly its entire useable life. There is no need to use a regulator with the A123 batteries unless you have servos that are listed as 4.8v servos only.
I would do at minimum a pair of 2300 mah A123's on your model. Afterall, even if you dont need all of there capacity for the model, they will allow you to fly more often between charges, and who knows, you may find that as a plus and that you really do need that kind of capacity. Batteries are cheap, Compared to replacing the airplane!
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Old Dec 28, 2012, 02:48 AM
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I don't think I've used any servo whose manufacturer is happy to guarantee them over 6V. When they say 6V they mean 6V not 6.6V or more.

Don't forget when you overvolt your onboard equipment the current draw goes up as well. That's when you need seriously more capacity in your pack.

I only tried a 6V system once and that was the model that crashed due to power loss. I have since stayed with 5V via regulator even for the real biggies - 144" DH Heron included.

My view is that there is no point going higher voltage. A standard servo averages 0.15 secs for 60 degrees of travel - way more than a slow-flying scale model requires - and if I'm worried about overall strength I wire trim tabs as servo-assist. This even works for the 115" Short Stirling with its 47.5" tailplane and full width elevators... same single standard servo but assisted by tabs and on 5V supply. (Though it has a HUGE 2S LiPo pack in the nose because I needed the weight there - probably run the radio stuff all day! )
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Old Dec 28, 2012, 04:31 AM
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Quote:
Wow, only 2000 mah for an 80" airplane! I use more than that on airplanes 2/3 of that size!
Its a 5000mah battery in the picture but it wont be the battery I actually use, I will stick with NiMh with this model I dont see any need for anything else, I run big helicopters on LiPo through a regulator but keeping it simple for this one, besides I want the weight up at the front
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Old Dec 28, 2012, 08:22 AM
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Originally Posted by eye4wings View Post
I don't think I've used any servo whose manufacturer is happy to guarantee them over 6V. When they say 6V they mean 6V not 6.6V or more.

Don't forget when you overvolt your onboard equipment the current draw goes up as well. That's when you need seriously more capacity in your pack.

I only tried a 6V system once and that was the model that crashed due to power loss. I have since stayed with 5V via regulator even for the real biggies - 144" DH Heron included.

My view is that there is no point going higher voltage. A standard servo averages 0.15 secs for 60 degrees of travel - way more than a slow-flying scale model requires - and if I'm worried about overall strength I wire trim tabs as servo-assist. This even works for the 115" Short Stirling with its 47.5" tailplane and full width elevators... same single standard servo but assisted by tabs and on 5V supply. (Though it has a HUGE 2S LiPo pack in the nose because I needed the weight there - probably run the radio stuff all day! )

Actually, the whole "6 volt" rating came about from the old days, when a 5 cell nicad batteries Nominal voltage rating was 6 volts. As technology changes, the term's never have. I have been using A123's on every airplane I own for over 3 years with no issues. Not to mention, I know of at least 100 other people who do the same with no problems at all.

Just because you had a model that crashed due to a power system loss that happened to be 6V doesn't mean that 6v was the issue! There are many more components and setup issue's that could of been the reason for the failure (battery condition for one).

I have also seen more failures, near crashes and crashes due to regulator failures than I ever have from a battery failure (post Nicad/Nimh days). IMO, if you have a battery technology that works fine (A123) with a minimum use of specialized items (regulators) in the system, then you are running a more failure resistant system and have less things to go wrong.


Here is a Good link with a FAQ On A123's. Many people dis-miss them b/c they are misinformed and think they are like a Lipo:
http://hangtimes.com/a123_batteries_for_giants_faq.html
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Old Dec 28, 2012, 08:23 AM
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Originally Posted by heli_madken View Post
Its a 5000mah battery in the picture but it wont be the battery I actually use, I will stick with NiMh with this model I dont see any need for anything else, I run big helicopters on LiPo through a regulator but keeping it simple for this one, besides I want the weight up at the front
Sorry Ken, that comment was meant for Casor's comment on having a pair of 1000mah nicad's for his plane.
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Old Dec 28, 2012, 09:46 AM
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Originally Posted by invertmast View Post
Just because you had a model that crashed due to a power system loss that happened to be 6V doesn't mean that 6v was the issue! There are many more components and setup issue's that could of been the reason for the failure (battery condition for one).
Quite so.. the comment was intended to support the reminder that the higher voltage means greater current drawn - THAT was the issue.

I don't recall the battery capacity I was using (1000mah NimH I think) but the model had 3 standard servos one mechanical retract job and one ESC. The first flight was barely 5 minutes duration and I expected to be able to make a second (and possible a third) flight on the same charge - and who wouldn't?
I think if I had flown on my usual voltage I might have made it, but there you are. We all tend to stick to what we know works and learn our lessons as we go.

That crash stuck a bit of piano wire straight through one LiPo cell and into a second. Killed the cells of course but contrary to the scaremongers there was no fire to guide us to the crash site - it took 5 mins to find it in long grass and the cells were just quietly fizzing their last.
You might think I should have gone to A123s after that event (for the hard case), but the lesson I took away from it was that LiPos were safer than reputed to be and that the videos gleefully put out by people to show how prone to explosion they were must have taken a lot of abuse to make happen.

Maybe it's just chance but I have never seen, let alone had, a BEC go down in flight.
Or maybe (to paraphrase Simon and Garfunkel) a man sees what he wants to see and disregards the rest?
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Old Dec 28, 2012, 10:01 AM
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Originally Posted by eye4wings View Post
Quite so.. the comment was intended to support the reminder that the higher voltage means greater current drawn - THAT was the issue.

I don't recall the battery capacity I was using (1000mah NimH I think) but the model had 3 standard servos one mechanical retract job and one ESC. The first flight was barely 5 minutes duration and I expected to be able to make a second (and possible a third) flight on the same charge - and who wouldn't?
I think if I had flown on my usual voltage I might have made it, but there you are. We all tend to stick to what we know works and learn our lessons as we go.

That crash stuck a bit of piano wire straight through one LiPo cell and into a second. Killed the cells of course but contrary to the scaremongers there was no fire to guide us to the crash site - it took 5 mins to find it in long grass and the cells were just quietly fizzing their last.
You might think I should have gone to A123s after that event (for the hard case), but the lesson I took away from it was that LiPos were safer than reputed to be and that the videos gleefully put out by people to show how prone to explosion they were must have taken a lot of abuse to make happen.

Maybe it's just chance but I have never seen, let alone had, a BEC go down in flight.
Or maybe (to paraphrase Simon and Garfunkel) a man sees what he wants to see and disregards the rest?
This will be my last Off-topic post for respect for Ken, unless he say's it's ok

I've seen both the good and the bad of Lipo's. I've seen some handled very carefully and be involved in a light crash (plane was intentionally landed inverted). the battery slid forward about 2" (it wasn't punctured) and errupted into a storm of flames.
Then again, i've seen some that were routinely abused and finally punctured in a fairly violent crash (full throttle, straight down) that were bent in half and 4 of the 6 cells punctured and them not go "boom".

Personally, the inconsistency and the Possibility in them errupting into flames in an aircraft carrying fuel (jet A, kerosene, gasoline, whatever) is enough of a reason for me not to use them. But when handled with care and the model constructed to avoid most any way for them to be damaged during normal use, they are perfectly fine as long as they are treated with respect.

A123's have never let me down. I use them in my GWS slow-stick and have on occassion flown them down to Zero capacity. They recovered with less than a 1% loss of capacity and out-perform the A123's who have been treated correctly. For Rx, ECu and ignition batteries, there's really no reason not to use them if you need weight! especially considering you can top them off with the charger in less than 10 minutes.
I have one model that has been sitting for 14 months with the A123 fully charged (I never got around to flying that model).. I just topped it off a week ago and it only took 15mah to top it off.
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