Thread Tools
Sep 17, 2019, 07:35 PM
Scale Aircraft = Scale Crators
mikejr83's Avatar
Thread OP
Discussion

Winch Resistors


I recently purchased a winch. For those interested it is a Bernie Sizer designed winch which is either the same or close to the one sold by by SoaringUSA: https://www.soaringusa.com/AC-NN-WINCH.html


The winch as I received it does not have an adjustable resistor as I've seen on the Ober winches. I got this winch to be prepared for F3J TS. It slipped my mind till the other day that it needs to be set to the correct resistance for competition. How should I go about making a resistor for this winch?


NOTE: This thread was originally started in the Sailplanes FS/WTB forum: https://www.rcgroups.com/forums/newr...ply&p=42759469


Quote:
Originally Posted by whacker
Hi Mike jr

You may want to do some research on current shunts, I believe there's formulas on length of shunt, based on cross sectional area. Stainless is a good material

Surely you could bend one up once you find the base of reference for testing the power loss across the shunt.

whacker
in the wet Waughs River Valley


Quote:
Originally Posted by Bmwjoon
Mike, that bar between the solenoid and the motor is the shunt. You would adjust that. Mike Lachowski just helped me test my winch this weekend. You need the whole thing hooked up and then you need to arrest the spool. I used by hands but you could use a clamp as well. You'll need to measure the voltage of the battery while the system is idle then you need the voltage and current of the system after it's activated (the FAI book says 30 milliseconds after you hit the pedal). There is a specific testing box used but you could test your own using a volt meter and and amp meter. Minimum resistance is 23 milliohms.

Take a look at the FAI sporting code for F3B, the explanation is very good.

Hope that helps. As long as you can adjust it, you'll be okay, you can adjust the winch at TS.


Quote:
Originally Posted by V1VrV2
I built a prototype F3B winch years ago and documented it here on RCG. The resistor used Manganin rods that could be slid in or out to change the resistance.
The resistance was tested by using an old "Der Windentester" electronic measuring device but nowadays they use a clamp OHM meter instead. Not sure which one but there might be more info in my RCG post here:

https://www.rcgroups.com/forums/show...=usa+f3b+winch

I never made any others as too many F3B guys wanted very individual specific things and that would have been a nightmare to produce them as individual winches. They all wanted it to be like an OBER but that was already available.

Manganin is hard to find. I had to order it overseas. There may be other materials not affected by temperature variances. Manganin is the best material for this.

Quote:
Originally Posted by mlachow
I have a little 1mm thick manganin sheet around. Enough for another 3 or 4 strips suitable for use as a resistor if it is a normal Bosch motor and with a normal battery, not a really high CCA, low resistance battery.

Last Bernie Sizer winch I tested that didn't have a resistor on it was in the 20 milliohm range with a bigger battery. Great for launches...... But far from legal.

The Ober resistor material is four 3mm rods. So for resistor length, a 28mm wide strip of 1mm is close to the four rods in ohm's/mm. The ober also has a slider and other brass pieces. So all the places you have metal to metal contact, you add a little resistance. The obers when adjusted usually end up around 2.5 inches between brass pieces that clamp on the rods.

The sheet I have is left over from when I built a bunch of winches a long time ago. It is crazy expensive if you just wanted to order enough for one resistor from Goodfellow. About $200 if you wanted just one. If you wanted enough for 20, then maybe it would be $25 a resistor. Or maybe there is some cheap source in China.

Probably the easiest to build would be some of the 8mm rod since then you only have one rod to adjust. It just reduces the surface area for heat dissipation.

The low budget and less efficient solution is to use stainless steel. Resistance goes up as it heats up.

The resistor will get very hot on a longer launch. It might be only 2 to 3 milliohms but when you put a few hundred amps through that. it gets toasty.


Quote:
Originally Posted by mlachow
It is in the F3j rules too.

https://www.fai.org/sites/default/fi...soaring_19.pdf See 5.6.8.2
It is 300ms, not 30.

Don't forget the general rules
https://www.fai.org/sites/default/fi...les_19v2_0.pdf


Quote:
Originally Posted by Bmwjoon
Yess 300 !

Mike you are the winch guru! I actually learned a lot, thankyou!

Joon
Sign up now
to remove ads between posts
Sep 17, 2019, 07:58 PM
Scale Aircraft = Scale Crators
mikejr83's Avatar
Thread OP
So after some back and forth with Mike I decided to get some manganin. I did revisited looking at how the solenoid is hooked to the motor. It appears that it is a piece of brass or copper and a "jumper" that could be a resistor.

The piece that I'm betting it's copper is going to have low resistance so I could add the manganin between it and the positive point on the motor. I know that I just can't just add more pieces for more resistance (resistors in parallel don't increase resistance). So I would have to make it longer. How would I make the pieces interconnect so that I can make this adjustable.

I don't want to guess and get to the contest and find out that my winch isn't legal or overly handicapped.
Sep 18, 2019, 09:14 AM
Registered User
Mike, it's my understanding on Bernie's winch where that flat piece of metal is between the motor and solenoid, there are supposed to be plates of manganin to adjust the resistance. If you look at Bernie's website he has a picture. I am unsure of the thickness and number of plates. Good luck, you should be able to figure it out.

Joon
Sep 18, 2019, 09:49 AM
Scale Aircraft = Scale Crators
mikejr83's Avatar
Thread OP
Joon, Share a link?
Sep 18, 2019, 09:56 AM
Registered User
Avaldes's Avatar
Mike, to be clear, you are going to remove the copper bus bar and replace it with the resistor that you fashion.
Sep 18, 2019, 12:37 PM
Registered User
https://nnewinches.com.au

In the gallery starting about 10 pictures down you can see pretty clearly.

Joon
Sep 18, 2019, 01:01 PM
Registered User
Quote:
Originally Posted by Bmwjoon
https://nnewinches.com.au

In the gallery starting about 10 pictures down you can see pretty clearly.

Joon
Interesting approach. Looks like only step changes are possible with that set up.
Mike clearly doesn't have multiple plates as shown in the link.

My preference is to put the adjustable resister on the ground side. I think it gives more configuration options. . .
Sep 18, 2019, 01:34 PM
Registered User
Quote:
Originally Posted by Kiesling
Interesting approach. Looks like only step changes are possible with that set up.
Mike clearly doesn't have multiple plates as shown in the link.

My preference is to put the adjustable resister on the ground side. I think it gives more configuration options. . .
I don't see how you can really fine tune the resistance like you said. Plus as Mike taught and demonstrated to me, each conductive point is another source of variability.
Sep 18, 2019, 03:35 PM
Registered User
Yup, each interface adds to the resistance. Which isn't necessarily bad, but there typically is dirt, surface finish differences, etc, that can change how much the interface adds to the resistance. That variability is not ideal.
Sep 18, 2019, 04:06 PM
Registered User
I sent mike a 4 inch long strip of manganin. If he cuts a slot in the copper bar for a bolt, and maybe two slots in the 1mm manganin sheet. Then makes a third piece that has three screw holes to use as an adjuster, it should work.


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Kanthal resistor for F3B Winch manic moore Multi Task F3X 22 Nov 02, 2014 09:34 AM
Discussion consequences of using a resistor array in place of burden resistor amnakhan786 New Forum Requests 0 Mar 05, 2010 02:04 AM
Question To resistor or not to resistor... SpeedVision DIY Electronics 5 Oct 12, 2007 04:01 PM
Discussion F3B winch resistors D_Ryan Multi Task F3X 2 Jun 25, 2007 07:21 PM