DIY Airbrake...

[rosspix]

This originally was to be an Airbrake w/out a rheostat but I found one in my
parts drawer.

Nice...

The fan isn't hooked up yet. I'm waiting for the DC jax and if that's a noise
maker I'll wire in a typical 9V connector.

Just as a thought - is there any way you could use the internal voltages to drive the fan? Not sure what impact (if any?) it would have on the final output... Something like this, maybe?

[img:875:563]http://www.rossedwards.net/wp-content/u ... 03/fan.jpg[/img]

Ross.

[zephody]

Noel Grassy: Thanks.

But rather I had the variable resistor and especially the clamps up against the side of the chassis see my picture. I bent the mount brackets toward the center of the box and now it works just fine

Do you care to explain that one again? I don't quite see the picture here.

I have a similar problem with the adjustable lugs on my variable resistor. I seems that they won't clamp firmly enough to make the connection. When I try to measure the ohms from the lugs to the other pole on the resistor, I get nothing. No contact.

Do someone have an idea of how to fix this?

[M Fowler]

zephody,

If you go back a few pages you can see I was calling my self a dumb ass because all the time I as having problems it was because I had my resistor to close to the chassis and my adjusting lugs were grounded against the chassis. So after I realized my stupid mistake I bent the mounting hardware straighter so it would pull the resistor further away from the chassis. I don't think you did the same thing did you? You said you removed the shipping strip off the adjustable resistor, I thought I read that in your post.

Your wiring looks correct to me and we have plenty of diagrahms from Bnwitt to help with that.

Mark

[zephody]

Mark,

Thanks, now I understand the problem you had. Mine is different, though. The lugs on mine are not in contact with the chassis, but as I mentioned earlier, they don't seem to be in contact with the metal on the resistor either. If I move the lugs and measure, I get nothing. (Yes, they are firmly fasten.)

From pole to pole I get 25ohms, which is normal, and if I place my multimeter probe somewhere into the chunk and on the right side pole, I also get the correct ohm values from point to point.

I've checked my wiring twice, so nothing wrong there either...

[M Fowler]

Make sure the adjustable lugs are on correctly as I due believe there is a small bump in one spot on the loop of the lug that contacts the adjustable resistor for contact. See those indentations on the lugs in this attached photo?

If they don't get tight enough to contact the resistor, then you take each one off and make then fit the resistor. You may need to put a noncombustable piece of something between the coated side of the resistor and the adjustable lug making sure the dippled part of the lug is against the bare part of the adjustable resisitor.

Mark

[bnwitt]

try lightly sanding the exposed wire on the tappable resistor with fine sandpaper to knock off the grey oxidation on the wire. That will improve your contact to the clamps.

[zephody]

Mark, bnwitt,

Thanks for answering.

Is it the brown or the grey part that is the insulation on the tappable resistor? I can't seem to understand how the lugs can reach the conductor part there...

[M Fowler]

zephody,

The resistor is coiled wire and the brown is an insolater. Barry wanted you to carefully sand on the wire to expose the wire since there maybe some residue from manufacturing.

This may be a dumb question on my part, but you do have the variable resistor and can see the wires right? Or is your resistor solid brown everywhere with no wires showing. The picture I include previously shows what yours should look like?

Mark

[Structo]

The lugs have a dimple that should make contact on the resistor winding.

The strip of exposed winding is the part shown in Mark's photo.

Take some 400 or so sand paper and sand across the strip of exposed wire.

Something doesn't sound right if the taps aren't making contact with the exposed winding of the resistor.

Can you post a close up of your resistor with your taps installed on it?

[zephody]

Mark,

It's an tappable resistor, all right.


Thanks for the answer, Structo.

The lug to the far right has contact, but not the other two. Seems there are dead spots all over the place.

Here is a picture of the bugger:

[M Fowler]

Yeah that is a variable resistor alright, now what?

Should get 6 ohm, 11 ohm and 16 ohm off the three lugs and this is a 25 ohm variable resistor.

[zephody]

Thanks alot guys!

I sanded of quite alot on the resistor and some on the lug too, and now it works perfectly.

[M Fowler]

Zephony,

That is great, nice to get something working properly and it is so strange that your resistor and lugs needed so much prep work. It shows that we should not just randomly throw parts together without inspecting them or preparing them.

Good work Zephony, hope you enjoy.

Mark

[Ron Worley]

I had to burnish the resistors too to get a good contact- they are apparently coated with something....

[ettepostkonto]

Hey Matt,

Here's my order from Mouser for the Airbrake parts:

(1) 546-1444-14 1444-14 Hammond Aluminum Chassis
CASE 9X5X2 $11.44

(1) 546-1434-14 1434-14 Hammond Aluminum Chassis
COVER 9 X 5 1 $4.38

(1) 588-L100J25RE L100J25RE Ohmite Solder Lug Power
Resistors 100watts 25OHMS 5% $9.45

(1) 588-RJS150E RJS150E Ohmite Power Rheostats 50watts 150OHMS $41.84

(1) 10WA365 CK1455 6.35X20.7MM FLAT SHAFT Lorlin Nylon Rotary Switches RTRY 2POL 6POS SLDR $4.33

(1) 588-D100K25RE D100K25RE Ohmite Adjustable Tap Power Resistors
100watts 25OHMS ADJ $16.86

(10) 588-2125E 2125E Ohmite Hardware ADJUSTABLE LUG $12.00

(10) 588-12-E 12-E-100 Ohmite Hardware RES MOUNTING BKT $5.30

Sub Total: $105.60

Hope that helps,

Andy

Hi everyone! I'm new here.

This thread has been extremely helpful for me as I'm a bit of an idiot when it comes to schematics and D.I.Y. projects. But now I'm just about to order the components and (try to) build one!

A stupid question though: Will the Airbrake work OK with both 8- and 16 ohm amps?

Edit: Never mind - I have since found Ken Fischer's article and I trust his judgement... At least with 8 or 16 ohm amps. From what I gather here - a 4 ohm amp might be pushing your luck.