3573 replies to this topic

[Michael Rigsby]

Custom X-12 arms !

Now there's a thought !!

I have a Heap of the Shorter Mura Blanks,..Whats a Custom X-12,..??,..ROFL
Heck for that Matter What Turns/Wire does an X-12 use anyway?

Answered myself, 50/29#

Stoo,

An X-12 is one of the classification of Group 12 arms for use in Box 12 wing car racing , uses 50 turns of 29 gauge wire, but the stack length is only .350 inches. Timing is normally either 38 degrees, or 42 degrees on the one's most commonly used, and can go as high as 46 degrees, though I know of no one using that high a timing in most of them. Stack diameter can be .510, .513, or .518 on some arms.

Michael Rigsby

[GTPJoe]

Michael,

X-12 arm diameters now go out to at least .540 and even maybe .560.

I know Monty at BOW got some .540 dia. arms approved recently for USRA racing.

See ya!

[Michael Rigsby]

Michael,

X-12 arm diameters now go out to at least .540 and even maybe .560.

I know Monty at BOW got some .540 dia. arms approved recently for USRA racing.

See ya!

I believe the arms that Monty sent to USRA were Contender, Stinger (Super Wasp), and Super 16C
in the .540 diameter, and yeah, they were approved. According to an Addenum published in October, all
group 12 arms are allowed a max. diameter of .540, but this is for Division 2 only. I haven't seen a regular X-12 arm yet in the bigger diameter, only the SuperWasp, and then only from Bow, not the major suppliers like Pro Slot or Koford.

Michael Rigsby

[havlicek]

I finished some quick and dirty tests using some brass cut into thin/small strips and bent to simulate a com tab with a piece of magnet wire layed in.


Test #1 clearly shows the silver and I think it's a bit heavy (although this stuff is almost pure silver and should be a great conductor.

Test #2 is a neater job with the silver barely showing. This stuff melts/flows at around 1200°F so I doubt there will be much trouble from these connections.

I made two carbon electrodes using "D" cell carbon/zinc batteries and shaped one down to test how their different sizes would affect the process. The larger carbon electrode is easier to control than the smaller one since it takes maybe 2 seconds to complete the "weld". The smaller one will almost melt the brass in that time and without some sort of timing relay to precisely control weld time, is too risky. Maybe if I get the timing setup sometime, I may try that one again for like 1/2 second or so.

I'm also showing the heatsink/negative electrode com connection thingie. When clamped with the negative lead, it tightens snugly around the com and should prevent any heat damage by siphoning-off heat. The whole process goes so fast that I don't know that the com would get that hot anyway, but it seems like a prudent measure to take.

I also did some tests with "SolderIt", which is a low temperature powdered solder/flux. It flows at only 450°F, but will only remelt at over 600°F. It works fine with an ordinary soldering iron and is probably good for really mild winds or even chassis work requiring extra strength (soldering-in a motor etc.), but I probably won't be using it for the com connections since brazing/welding with silver doesn't seem to be much of a problem.

***Note: The above is for informational purposes only. If someone tries this stuff and blows themselves up, tough luck

[LindsayB]

I think getting the silver solder thin now is the key. I have heard of people running this thru a tool to extract it about the thickness of 22# piano wire.

Have u setup a foot operated relay yet. I will look around for some variable timing circuits.

[Jairus]

The above was preformed by a professional on a closed course. Kid's don't try this at home...

All kidding aside, I am very impressed John!

[havlicek]

Hi Lindsay (and thanks again for pointing me in the right direction),

I don't see the diameter/gauge of the silver as a problem, I ordered the thinnest wire I could find and what I have here is pretty danged thin. I also have some of the same silver (so-called "EZ" grade that melts at a bit over 1200°F) coming as a paste/flux combination. That way, I can put a bit on the com tab with a toothpick before I crimp it. That would free-up one of my hands since I wouldn't have to hold the silver...it would already be on there.

If you can show me a simple (ie...for dummies) way to wire the thing with a list of parts, I may just do that. I've got a HD momentary footswitch with 40A contacts coming which should be a help also.

Hi Jairus,

Nothing to be impressed about (but thanks!), especially compared to what you do! I just pestered Lindsay and some other folks until I was semi-clear on what I needed to accomplish and then spent a bunch of quality time on Google I (ahem) think this should be the last bit as far as getting the armns up to snuff. Of course, I could start figuring out how to cap the coms also ...NAH!

-john

[havlicek]

I had some sort of vintage EBD arm here that someone else had epoxied. I was able to carefully saw off the old magnet wire and figured this would make a good test for welding the com since I don't have any use for an endbell drive arm anyway. I put on a Kirkwood com (very little advance...around 10° or so), did a #25 wind and it all sounds fine and looks fine...although a little sloppy. Practice should help tighten things up, but what I was a little worried about (damaging the com) turns out not to have been a problem. If anything, the possibility of heat damage may be less doing it this way than soldering because it happens so quickly.



-john

[Michael Rigsby]

Very nice looking arm, John. I would think, like you, that this would spread less heat through the arm since it does happen so quickly and less heat is always good. Looks like a good arm for a classic eb drive inline all brass chassis setup.

Michael Rigsby

[havlicek]

Very nice looking arm, John. I would think, like you, that this would spread less heat through the arm since it does happen so quickly and less heat is always good. Looks like a good arm for a classic eb drive inline all brass chassis setup.

Michael Rigsby

Thanks Michael. On the arm itself, I guess it might be but I don't personally have any use for it. I needed to actually try welding on a real arm instead of just pieces of brass...so it served my purpose

-john

[Dan DeBella]

Michael, We have been making x12 arms in .540 for well over a year now, along with SW, Cotender and big diameter 16C, 16D and S16D. Available at all of the distributors and in our catalogue.

[Jairus]

I can think of a use for that arm...

[havlicek]

...say no more Jairus, it's on the way For all I know, the original arm may have come from you anyway (I forget this stuff ) , so it's fitting if it makes the return trip.

-john

[havlicek]

Here's a new one with all the doo-dads on a longer blank

-.007" lam arm

-welded com tabs

-approx 17° advance

-.490" stack (finished length approx .495")

-hi-temp epoxy

-#25 awg



-john

[TSR]

John, you are getting better...

[Jairus]

Better? Better? Better?

He is the BEST!

[havlicek]

Merci beaucoup Philippe I'm nothing if not persistent. Thanks also Jairus...that EBD arm is on the way with some added goodies .

-john

[havlicek]

I forget where I saw it, but someone posted a picture of a Pooch #26awg here a while back so I wrote down the wind did the same here on a new Mura .007" blank. The com welding is a little sloppy, but I'll refine that as I go. I've also figured out a better way to polish the stack that I used here. So bit by bit...



-john

[havlicek]

I just did this #24 and when spinning it up, it sounded rough and was drawing almost 7 amps. It also was arcing noticeably at the com, a sure sign that something isn't right. When I put it in the com lathe and marked the com with a sharpie, the first pass revealed that the com was pretty far out. A few passes later, it looked fine and this time it spinned smooth and current draw was down to around 3.7 amps. Considering the cost even of the raw materials for winding these things let alone the time involved, the Xipp com lathe has been a really useful tool!



-john

[Jairus]

John,
You are the best to be sure. If we had a true RETRO series to play with you would be KING of the ARM WINDERS!

I have three silver wire re-wound arms here purchased in a trade... would you consider testing for me?

[havlicek]

Hi Jairus,

It's easy to be good at something (relatively speaking) when you're the only one doing it I've tried my best to get other folks back into winding, but have only had really limited success. It seems clear that people will be most interested only in what they can run in a sanctioned race. Not many people who'll build stuff just to run for the heck of it. On the arms themselves, I'd love to come up with another affordable source for blanks and coms but have totally struck out besides Mura. It could be that the cost is keeping the few people who are interested from trying their hand at it again. Even some nice used arms that haven't been balanced and epoxied for rewinding would be cool if the stacks and coms are good quality. It was great when all this stuff was "off the shelf" at your local track/hobby center.

Sure I'd check those arms for you, but there isn't much to that unless you also want me to cut the coms and give them a spin. The epoxy on some of those old arms is probably getting brittle by now, so I'd go slow. Oh yeah, I don't have any 26D setups either.

-john

[Prof. Fate]

Hi

John, I still wind. Have to to keep the oldies running! One of the reasons I can call to mind what winds and when in our conversations. However, even IN the day, almost everyone bought arms rather than wind. In the day, winding helped pay for my program by selling arms. I only knew two other people in my area with thousands of racers who wound.

When someone said "I got a rewind" it was that they had bought an obsolete kit with the 1 buck "dyna rewind" upgrade!

I have told the story that the first arm I used that wasn't my wind was a Bob Green arm in about 70. When I talked to Bob years later, I framed it as a compliment!

I LIKE building. Racing is extra credit.

Fate

[Jairus]

I LIKE building. Racing is extra credit.

Agreed!

[Bill from NH]

I like building too, but much of mine is woodworking.

[havlicek]

Hi Rocky,

I think we've sort of touched on this before, but in the mid to late 60's (the timeframe is a guess) a whole bunch of my friends and I were winding everything we could get our grubby little hands on. We had a pretty nifty little competitive thing going on trying to one-up each other. While I ran at one particular place in Queens NY, we did travel around a little and every place we went they had armature blanks, coms, wire and the crank winders for those who wanted them. Even a couple of years later when I moved to Long Island and went Phaze III in Farmingdale, all the stuff was there for winding even though the hot factory "rewinds" were all over the place. Of course, more people bought "rewound" arms than did them themselves...but a LOT of people also bought scratchbuilt chassis too (Roy was the first guy I saw that tumbled chassis). Good quality blank arms were cheap then, I shoulda stocked-up!

-john