For you folks with bigger elecs....

[Vamooska]

Mark Jones and Vampowerpro proudly present:
THE JONES WITCH

Why it is needed
As electric aircraft become larger, the motors that power them also become more powerful. The lithium batteries that inevitably find themselves in their fuselages also increase their power and range. As most of us have experienced, motors can and do from time to time, power up unexpectedly either from an inadvertant bump of the left stick, reversed channel, a "borrowed" frequency or simply a radio freq hit. With the larger power systems now used...this gets to be extremely dangerous. Just ask the four fingered guys at the field. With no audible warning as in a gasser or slimer engine running...the risk is even greater.

What does it do?
This switch mechanism enables the battery or batteries to be connected in an airplane just as before, but now..the esc and receiver are not activated until you are ready to be airborne. This allows the pilot to install the wing, make all necessary adjustments, and attach other flight gear in the danger zone, without risking injury due to a prop strike.

How do I install it?
If you can solder and put together an ARF kit, this will be a piece of cake. All you need to do is solder your connector of choice to the wires, drill a small hole in the fuselage for the mount...push the switch through the hole from the inside screw in the bulkhead bolt and plunger rod and you are finito! You may want to reinforce the sidewall of a thin airframe with a small piece of ply as the Jones Witch has a positive locking mechanism on it that offers a bit of resistence when the plunger is pulled. This is so that it doesn's accidentally shut off.

How much and where do I get one?
The current 60 amp model is 13.95. You can order one right now from sales@vampowerpro.com . They will be at www.vampowerpro.com soon.

I have a plane with over 60 amps continuous current...will this work?
I wouldnt risk it. We are getting some that can handle up to 100 amps continuous so wait for those!

This was in the new product showcase at SEFF with great results!

Notes:
The Jones Witch is trademarked and is patent pending.
The switch is only available from Vampowerpro.com

Click here (http://www.vampowerpro.com/Vammy/Jones_Witch.mov) to see a movie of the Jones Witch. The movie is 8MB in mov format. You can right click the link and choose "save target as" also.
Please visit the actual sale thread located here (http://www.rcgroups.com/forums/showthread.php?t=530366#post5616750) to purchase

Thanks
Vammy

[d-bledsoe]

I'll try one... I have a sig somethin' extra that im in the final stages of conversion/completion so that will be the finishing touch. Cant wait to try it out

Payment sent via paypal.
-Derek

[Vamooska]

Very good....goes out first thing.
Vammy

[BEC]

Well that's an interesting combination of shortened Anderson Powerpole housings and the old DuBro internal receiver switch mount..... What are you using in there - the APP 45A contacts?

[punkindrublik]

Ordering one shortly. Thanks Vammy!

Brian

[Vamooska]

Yes they are 45's which will easily handle the 60amps. There are more parts in there though :D The wire size is 12 AWG high quality noodle wire with silicone insulation.....just like battery hookup wire. The discharge form the capacitors will not cause pitting in the contact area either...that is definitley a plus! My Texan pictured is a 6S4000 powered Himax 5018-530 that pulls 59 amps WOT.....no power loss. I have a table that shows minimal loss of 1.06 watts at max load as tested.
Also look for these in the upcoming Model Aviation News. For the larger (100+ amps) models we have a real neat pre load feature to eliminate any sparking at all. :D
Peace to ya
Vammy

[Larry3215]

Vammy, you may want to re-think the pre-load feature.

There were several long discussions on this issue a while back (mostly in the heli forum - they were heavily into hi voltage before planes were mostly) and as I recall, both Castle Creations and Schulze both recomended against slow charging the esc caps.

IIRC it was because it could mess up the initial voltage measurements the esc's do on power up.

You just have to live with the pitting.

Becides - the newer HV Castles have that feature built in I believe.

Larry

[bhchan]

I thought you said "bigger" electric! 60 amp is not enough! :)

Brian, an EAJ

[Vamooska]

Wow great info there. We are precharging with a 35 ohm resistor. You are right though...cant really see if the ESC likes that or not. It may affect that. If pitting DOES occur, it will be at initial contact point and not resting contact points...so thats good. Thanks for that piece of info...very helpful.
We will also be modding them to include the other wire too so that all you have to do is solder on the connector of choice to them.

BhChan, We are doing just that. The very near future versions will be much larger and will hopefully handle the 100 amp curve. Will that do it?
Please let me know.
Vammy

[Larry3215]

Vammy, I forgot to mention one other thing you need to be carefull with slow charging/pre-loading the caps on the esc.

If the resistor is too large, the caps wont fully charge and you still get the spark and pitting.

If the resistor is too small, the caps will fully charge - and the esc can arm itself which defeats the purpose of the disconect.

The problem is - the correct size for the resistor is different for HV packs than it is for small low voltage packs. It is also different for different esc's. Depends on the size of the input caps to some degree, but input voltage is a bigger concern.

One size does NOT fit all applications.

If the controller does arm and if the motor tries to start - your little resistor will glow bright red and burn to a crisp very fast.

Ask me how I know :)

Larry

[Vamooska]

I think we have decided not to go with a precharge because of the controller sensitivities as mentioned. Check the above post to see in the pic that if there ever was a pittin gissue...it would be in the initial contact area...not the resting closed area.
Your input was very helpful too and thanks.
Vammy

[Larry3215]

:)

Larry