Master Contactor to Starter Solenoid & Main Bus.

The plans show using a copper bar to connect the master contactor to the starter solenoid. This point is also the the main power lead to the main buss (as far as I can tell). I used some .125 copper bar for the master-to-solenoid connection, but this doesn't leave much room on the master contactor stud to add a connection to the main power circuit.

It seems to me that .063 copper bar would do the job and be a lot easier to work with. The only problems is that I can't find any place to buy it. What have other people used and where did you get it?

BTW. I'm using the B&C contactor & solenoid which require a 90 degree twist to connect them - not as simple as the Van's components.

Try wiring your main feed to the input terminal of the battery contactor. It should be the same as going from the output terminal of the master except that the stud is longer (at least on mine).

EDIT DOH, I meant to say the input of the STARTER CONTACTOR! Not the battery contactor (that would be always hot) DOUBLE DOH!

Jekyll

Model airplane store

I bought 1/16" brass strip at a model airplane store. For now, that'll do until I look up the conductivity of both brass and copper and see if they're close enough.

As far as not having enough room on the stud, one thing you can do is lengthen the copper strip enough to add another bolt to it, and then attach your bus feed wire to that.

Whats the advantage

Rick_A said:

BTW. I'm using the B&C contactor & solenoid which require a 90 degree twist to connect them - not as simple as the Van's components.

Click to expand...

Can you return it and get standard contactors like van sells? I am not sure what the advantage is of the different style contactor?

Rick,

The plans actually call for two parallel strips of 0.063" copper between the master and starter relays, so your 0.125" strip should be just as good.

I am also using the B&C master relay, because they seem to sell high quality stuff and it's a drop-in replacement for the one Van's sells. However, I went with the Van's starter relay, because as you mentioned the B&C one has a completely different terminal arrangement. The Van's starter relay also has pretty long terminal posts on it, so I am planning to bring power from the relays to the main bus via a copper strip like in this photo from Checkoway's site.

btw, you can buy 0.063" copper stock from Van's here

mcb

Copper tubing

I used a piece of copper tubing. I put it in a press between to piece of steel. 10 tons of pressure and I had a nice flat buss strip. It has been working great for 150 hours

Jim
RV-6
Burlington Iowa

New old ideas

N24YW said:

I used a piece of copper tubing. I put it in a press between to piece of steel. 10 tons of pressure and I had a nice flat buss strip. It has been working great for 150 hours - Jim, RV-6, Burlington Iowa

Click to expand...

Nice to have equip.

Contactors: Master, Starter solenoid or relay.

Look Van can be cheap and there is always a gold plated solution, but these contactors are as good as it gets. The ones Van sells are Cole-Hersee have been around a long long long time; these contactors have been made by them and others almost identically since who knows WWII. Like so many things electrical on light planes they are adapted from the auto/truck industry. These contactors are all car, truck, folklift, farm equip stuff.

To answer my own question about why the B&C unit is better, I seriously doubt there is anything better about what B&C sells in regard to contactors. Now I have found cheaper prices than Van's but not better contactors, because they are all the same inside and made in simular shape and sizes. Yes there are different shapes and terminal arrangment, but inside is a coil, plunger (solinode) and two contacts.

There is a new TYPE or design I find interesting and thought about using it, a Tyco kilovac relay. http://relays.tycoelectronics.com/datasheets/ev200.pdf

It cost about $120-$150. It would be used for a master. The cool part is its huge volt opening rating, more than the standard we use, is small, about the same weight, and it only takes 1.7 watts, about 0.10-0.13 amps to hold closed. A standard master contactor takes almost an amp of current (14 watts) to hold closed and gets too hot to touch. It uses some kind of magnetic latching and is failsafe, so if it fails or power is lost it opens the contacts.

Now the above is not to be confused with a true latching solenoid, which have been around for a long time as well and do not cost much more than what we currently have. The down side of these types are that can fail closed. "Latching contactors" will use power to switch and than require no power at all to hold that position, closed or open. There used in boats, large trucks and industrial equip typically. They would work in a RV and save the extra heat and current to hold it closed, but are not good choices because you can end up with it closed and unable to open under some possible concevable conditions.

The problem with true latching contactors is not the case with the kilovac unit I mention above, which is held in closed position with linkage and a magnet and is ready to "spring" open at all times, requiring very little current to keep it close. The down side is cost and it really does nothing more than save an amp of current. The kilovac is made to high standards of operating conditions, vibration, G's, temps and so on. Still for 6 times or more money its not value added.

I guess I'll stick to the plans. The ones Van sells have long studs and can accommodate several lugs plus a thick strap, washer and nut.

George, thanks

for the interesting info. Since I already have the B&C parts, I will use them. The Master contactor mounts just likes Van's and has the same stud orientation. The Starter solenoid mounts the same, but the studs are oriented differently. When I bought them, I did so because I thought they were higher quality, but as you pointed out, there may not be much difference.

My real question has to do with the inter- connects. Van's shows using 2 strips of .063 copper bar. Are 2 strips really required? Would one piece of .063 do the job? I made the jumper from the master to solenoid using .125 bar (which was a challenge, but I did get it to fit), but there is not enough room on either stud for a second piece of .125 to connect to the next part of the positive side circuit. (It looks like an ANL current limiter should be the next component in the circuit)

I went from there (left side of starter contactor) to the ANL... and there's just enough room to get all of those bars on.. so you should be OK.

Rick,

I think the reason you need 2x 0.063" strips (or 1x 0.125" strip) between the master and starter relays is to handle the zillions of amps of starting current. But the next connection downstream that you're talking about only has to handle the operating loads of the rest of the aircraft, not starting current, so it doesn't have to be as beefy. Seems like you ought to be able to determine what gauge of wire you'd need for the relay-to-current-limiter connection (based on your load analysis) then check the cross sectional area of that wire vs the area of a 0.063" copper strip, and be good to go.

mcb

A Zillion is a lot

mburch said:

Rick,

I think the reason you need 2x 0.063" strips (or 1x 0.125" strip) between the master and starter relays is to handle the zillions of amps of starting current. But the next connection downstream that you're talking about only has to handle the operating loads of the rest of the aircraft, not starting current, so it doesn't have to be as beefy. Seems like you ought to be able to determine what gauge of wire you'd need for the relay-to-current-limiter connection (based on your load analysis) then check the cross sectional area of that wire vs the area of a 0.063" copper strip, and be good to go.

mcb

Click to expand...

Actually its about 320 amp MAX for short periods. Since the distance is short 0.063 would work but would have more voltage drop and build more temp, but for short start burst this is min. Lets say the hole for the lug is 5/16 = .32. Assume the strap is 3/4" wide. The total area is (.75-.32) x 0.63 = 0.027 in-sq. This is about 1/4 way between a #4 and #6 wire. Well the voltage drop for a #6 wire is only 0.07 volts (assuming 350 amps and 0.5 ft and 0.021 in-sq equiv to #6 awg). The temp for continuous ops would be too high even with twice the area.

Think about this. Take a case where you are using a large wire say #1 or #2 and the first part is the "Lug". The 0.63 copper strap is not any worse really if the lug thickness is the same, at least in the contact area. In reality 0.125 is too thick and 0.63 is a little shy but would work. One thing you could do is make it wider. Assume you need 0.05 in-sq. So 0.05 = (X-0.32)*0.063 > X = approx 1 inch wide.

In a word this metal part will get very hot. Ideally you would need the cross section but 0.063t will work is about 1 in wide.

Here is more info. From what I am reading and all my data you should have at least 0.035 in-sq (about a #4 wire).

When you look at it AREA, it has to do with length of the wire (strap) run, amps carried, desired voltage drop, max temp and weight.

Since the strap is out in the open you don't have a heat problem, and the time you run it is short and it has time to cool. I you arbitrarily want to keep it under say 400F for continuous op (which is not a bad idea) you would need more area, say the size of a #2 wire (about 0.0521 in sq). A 0.75 in strap X 0.125 in (with 5/16 hole) gives you that. Do you need the thickness? Well not really but it can't hurt. The length of the strap is so short that weight is not an issue.

http://www.skytecair.com/Wiring_Experimental.pdf

PS: The starter relay that B&C sells not only is harder to install, it may not made for vertical mounting? In the past van suggest you mount the relays (contactor's, solenoid), both starter and master, side ways to avoid the effects of G-force during maneuvering. In the past pos G's could engage the starter contactor. Well the side ways solution caused great wear on the contactor size the solenoid was galling in that position. The solution was to mount the starter relay upside down so pos G's caused it to stay open. Since Neg G's are less this works. Master relay you want Pos G's to keep it closed. My point is, are the B&C units made to be mounted on the vertical?

A piece of .063-1/2" x 12" costs only ~$2.00 from Van's. Just ordered mine a day or two ago that they packed with some backordered stuff. Although I curious as to why it is not included in the FWF kit, it's cheap to use the two .063 pieces. Not sure if .125 stock is any more expensive.

Two strips....

mburch said:

Rick,

I think the reason you need 2x 0.063" strips (or 1x 0.125" strip) between the master and starter relays is to handle the zillions of amps of starting current. But the next connection downstream that you're talking about only has to handle the operating loads of the rest of the aircraft, not starting current, so it doesn't have to be as beefy. Seems like you ought to be able to determine what gauge of wire you'd need for the relay-to-current-limiter connection (based on your load analysis) then check the cross sectional area of that wire vs the area of a 0.063" copper strip, and be good to go.

mcb

Click to expand...

I believe the copper strips are 1/2 inch wide....

If that is the case, 2 strips are equivalent to between #1 and #2 wire...

1 strip is essentially #4 wire.

If you are using #2 wire for your starting circuit, you should use two strips between the contactors.

Numbers here...

http://www.thepanelshop.com/Wire_table.htm

gil in Tucson