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Author Topic: E-36 "Puzzle"  (Read 9479 times)
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che
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« Reply #125 on: March 21, 2017, 09:00:45 AM »

(Apologies in advance to Tapio ...............)

Alan,

Thanks for your time in considering this question. I suggested a multiple pulse avoidance delay (MPAD) a few responses back so we seem to be gelling on what MAY work (legality ignored, after all this is for trimming and can be disabled).

I do see circumstances where those of use without the skill, experience and general craftiness of people such as Prof. Thompson would need to and can successfully stop an engine and then DT (via separate button pushing) without breaking the wings, so it is a realistic scenario. I also think that data on the Bauer system at least might be available. The question is would you want to provide a 2nd system for what might be a small market ?

The issue of multiple pulses being sent and their legality is I suspect a red herring as this was used in the original (?) RCDT system back in the mid 80s, in fact it was a requirement of the receiver to get, if I remember correctly, two coded pules within 0.25s or else the DT wouldn't operate. If not legal then a switch would be required to send just a single pulse when the unit is being inspected I guess................

CHE

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afb
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« Reply #126 on: March 21, 2017, 01:29:50 PM »

Che

The Bauer instructions give insufficient detail for *my* purposes - I've mailed Ken for further clarification.

Alan
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rivers
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« Reply #127 on: March 21, 2017, 04:44:32 PM »

Hi all, For what it's worth I build my own RDT systems which closely follow the Bauer format, except I use spread spectrum (LoRa) transceivers for greater range. When the transmit button is down RDT pulses are generated at an 8 per second rate continuously. The pulses are negative going 50 ms wide.

I think it's a good idea to have continuous pulsing. At long range the target model may be low, with the line of sight not so good, as well as RF propagation difficulties. Multiple shots are a help.

I don't think the Bauer system was originally conceived with motor stop on mind. Nevertheless, it works well with timers configured to stop the motor with RDT. My own timers are designed to stop the motor then automatically DT 1.4 seconds later. I think the FAI rules for contest flying are pretty clear on this, any use of radio must end in DT.

 
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rogermorrell
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« Reply #128 on: March 22, 2017, 01:00:59 PM »

As one of the originators of this RDT stuff along with Ken Bauer I support Dick Ivers comments - I think the RDT Tx should send multiple pulses
"to make sure it gets through". I have tried different other "clever" combos of pulse sequences etc and with the simple radio protocols we use they are just not reliable.   To reliably have some more complex system you need to have a 2 way transmission between the two radios so they know the signal was successfully received.    Ken is a F1A flyer and at the time we did the original work most power flyers would not entertain using any form of electronics so the possible need to stop the motor then activate the after a delay D/T did not arise.

Because in my MAGIC timers I let the sportsman decide what actions to take on the receipt of the RDT signal he can decide what actions and sequences are appropriate for his particular model - shut off motor/engine, pop stabilizer and/or wing, move rudder etc possibly with delays.  I also agree with Dick that rules say the object is to terminate the flight of  the model i.e. D/T so that has to happen. 

In the early days of F1Q in the USA I observed some people in a FF competition using  a regular R/C system to cut the motor and later D/T the model. That is clearly outside of the rules.  You might want to use this during testing.

I have built timers that would let you use a regular R/C Rx as the RDT system - where for example using the throttle stick to do from full throttle to full slow would D/F the model, the timer making the decision based on the length of the pulse.  The ideas was to see RDT costs coul;d be reduced by using an inexpensive regular R/C set instead of the more specialized and expensive RDT. Nice theory but cheap, small R/C sets don't have the range required to RDT  a performance FF model.

Roger
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Tapio Linkosalo
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« Reply #129 on: April 17, 2017, 12:38:19 PM »

Let's return, from RDT, back to Puzzle. I have been lately toying the idea of trying a single-bladed prop. eCalc suggests that a 7x6 single-blader should produce slightly more thrust than 6x6. I would assume that the prop is more efficient, with the area being in one wider blade than two, and also the increased prop disp diameter should add to the efficiency. Also single-balder should be straightforward to make a folder.

So I took an APC prop, saw off one blade. Drilled a hole for the pivot pin, filed the root to fit in a folder hub. Made counter-weight holder from aluminum, and added some brass nuts for counter weight. I still would need to find a means to properly balance the setup (and most of all to figure out how to balance. I recall reading a paper in Aeromodeller suggesting that the counter-weight should be a bit lighter than the blade. But cannot find the paper.) I did some rotation tests, and the vibration is not bad, also the blade can hang on at 13000 rpm. But as you can see, my counter-weight holder is too weak, and starts to bend. Gives you some impression of the forces involved.... Also, the one blade of 7x6 weights over 5 grams, as much as the whole 6x6 prop. Too much, as I already have problems with the CG being too far forward. The 7" APC blade is quite wide and thick, so I suppose I could make the blade much lighter out of carbon fiber and foam/balsa core. But maybe I first try to find good balance for the blade and test if I can get more thrust out of it. Also if I make a mold I need to move the pivot point, with this one the blade does not fold past the motor, but remains sticking at 45 degrees...
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JohnOSullivan
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« Reply #130 on: April 17, 2017, 01:58:58 PM »

Might be worth using already usable Graupner CAM prop blades. eg 7.5"x4" at 3.2 gm per blade.  
Adding the counterweight is going to add considerably to the total prop weight.
Also consider moving the counterweight outwards on a wire as per the old Rubber model single blade Props.
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John O'Sullivan
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« Reply #131 on: April 17, 2017, 11:55:14 PM »


Those CAM blades do not have enough pitch, I need that 5.5 to 6" for a DYS motor turning 13,000 rpm for enough forward speed to climb enough. With 4" pitch the motor should be turning 20,000 rpm, which would need a kV like 4000 I guess. Have not seen such motors.

 
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che
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« Reply #132 on: April 18, 2017, 10:16:09 AM »

Tapio,

I've been using the 7x6 APC modified to a folder and suspect with a single blade you could go to an even larger diameter. One issue is that the balancing would only be correct at one rpm but if you're still intending to use a governor function then maybe that would work. Agree that you need less mass at a longer moment to keep the wight down.

The reason the aluminium bracket bent is quite obvious I'm afraid.

CHE
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RayE
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« Reply #133 on: April 18, 2017, 07:35:00 PM »

Tapio,

I have been playing around, on and off, with the use of large diameter single bladed propellors for F1B and F1G. In doing this I came  across 3 papers which you may find of interest in relation to what you are doing;

- Design considerations for one bladed propellers   by Hewitt Phillips   ( NFFS Symposium 1971)

- Single blade propellers for F1K, why?  by R Hoebinger      ( Free Flight Quarterly  January 2004)

- F1B Enjoyment and the single bladed prop   by George Matherat and Jean Wanzenreiter     ( NFFS Symposium 2005 )

Phillips proposed that, compared to a 2 bladed prop, the diameter and pitch should be increased by 10% and the width by 75%.  I increased the diameter and pitch as suggested but only increased the blade width by a small amount. I have since produced a much wider blade but have not yet tried it.

Ray
 


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Tapio Linkosalo
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« Reply #134 on: April 27, 2017, 12:35:26 AM »

The mailman brought this yesterday.eCalc suggests 10 more Watts than my previous DYS motor. Maybe 180 meters on 10 second motor run with this one?
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