65 replies to this topic

[MSwiss]

If I get time, I'll elaborate tomorrow, but the timing not being exactly what is engraved on the stack never kept anyone from winning a slot car race.

[Ben Morrow]

Mike, 

 

Good Morning!  No need to waist your time. Winning races is not the point. The point is, why put the timing on the stack if not correct. It just seems a waist of time. Don't want to ruffle feathers here.

[MSwiss]

When the comm is set, it is on an unground arm, with hysol encasing everything you fixture off of, so you are not referencing off of a precise surface.

Also you are referencing off of only one slot. The slots are seldom a perfect 120 degrees apart.

Once the comm is set, it is put in the oven, for the epoxy to cure. It is no longer in the fixture, as the armature are made four dozen at time, not one at a time.

Whether it wanders a degree or 2, while in the oven curing, I don't know.

Even if you made 48 expensive fixtures, again you are working with an imperfectly-shaped item.

The arm gets finished and racers check it with an imperfect measuring device.

You are relying on the arm to sit "flat, on two tips of rotor, that is constructed from imprecise stampings.

I'm not familiar with how accurate the Go Fast timing measuring device works, but when I worked at Koford, there was only one way, with an approx. $10K optical comparator.

That transcends relying on the arm to sit perfectly flat, and will confirm how imperfect all these little armatures, that still perform extremely well, are.

[Ben Morrow]

Thanks,

 

Thats all very interesting information, always wondered what the steps were in arm manufacturing. However on many arms the bottom line is that the timming on the stack in many cases doesn't match what the timming really is. 

 

Ben

[havlicek]

Here's a little tidbit about all this:
 

Thats all very interesting information, always wondered what the steps were in arm manufacturing.

 
First off, comms rarely fit a shaft so snug that you can set the timing, remove the arm from whatever gauge you're using and then "fix" the position of the comm without it moving before you tug on it while winding. Matter of fact, some comms are a relatively "sloppy" fit because of imprecise boring, and that just drives me nuts (and also can mean other issues not related to timing). I take an extra step to make the comm only "barely movable," and then still check timing before and after winding to see if it moved... before epoxying, because it sure isn't going to move afterwards. Add to that the imprecise nature of many/most/all gauges, and there is certainly room for error or at least straying from the stated advance number on the package.

If you use a protractor (which is fine) to set timing. The 2mm hole you drill needs to be precisely at the intersection of the various degree lines scribed into it, and it should be close to the level you need to have the arm sitting flat on your (hopefully hard and smooth) work surface without the arm... or the protractor. If you are "off" by even a few degrees, take comfort in the fact that the manufacturers are also. 

 

Oh and, as Swiss pointed out, being off like that won't stop you from winning a race.

[MSwiss]

Ben,

 

I thought I just explained the difficult logistics to get them all "perfect."

 

Maybe you should try installing 48 comms, on 48 hysoled blanks, in 20 minutes, and see if they all wind up identical, and match the perceived timing from another party, measuring them.

 

Racers are more concerned that the winds don't shift, the lams don't mushroom, or the comm doesn't blow, vs. whether the arm being 36, 37, or 38 degrees, and matching the engraving.

 

(Was posting this as John H just added his above; great insight)

[Phil Smith]

It will depend upon where you drill a 2mm hole for the arm shaft & how you intend to keep everything level. From the pictures, the distance from the protractor's bottom edge to the point where all the angles start, appears to be less than an arm's diameter. Maybe not?

 

It's far from perfect, but with varying diameter arms and pole gaps, how do keep any of them level?

 

I think I can get an accurate hole, and get it level. The main appeal is that it's small.

[Bill from NH]

Use a thin wedge to keep varying arm diameters level.

[Ben Morrow]

Bill,

That's just what I'm thinking.

[MSwiss]

Obviously not a deal breaker for most racers.

No matter what time of the year it is, when I order custom arms, it's a four-week lead time.

I receive them 75% of the time, in the quoted four weeks. If I'm lucky, I get them in three

I was GM at Koford for 19 years and witnessed him working 75-80 hours a week, to make the best armatures possible.

I've explained the obstacles to getting them dead on. John has tried, also.

If you elect to ignore the experts and insist it should be better, without ever mass producing armatures yourself, that's your decision.

IMO, not a good one.

[havlicek]

Hi Ben,

I don't know if you've ever tried it, but try setting the timing on an arm and see what a tiny move of the comm does for timing. It can be a real shock the first time when you make a move so small you're not even sure there was a move and the comm changes by 5-10 degrees!  I think* that all arms are made to within a certain "tolerance," and the cost/labor involved in making arms is not insignificant. If a shop were tossing arms outside of the narrowest range for "perfect," a lot of perfectly good and maybe even race-winning arms would wind up in the garbage.

[old & gray]

Diameter x pi / 360

or

For a .210" comm diameter, .0018 inch changes the timing one degree.

Edited by old & gray, 15 May 2018 - 12:59 PM.

[Cheater]

Ben,

 

I think you're being a little obsessive here.

 

As has been pointed out, none of the arm makers have been able to generate the kind of timing accuracy you're wanting. Can it be done? Sure, if people are willing to pay the price it'll cost.

 

Virtually any manufactured item carries a dimensional plus or minus tolerance and it is a given that the smaller tolerance, the more the item costs.

[Ben Morrow]

I don't know if you've ever tried it, but try setting the timing on an arm and see what a tiny move of the comm does for timing. It can be a real shock the first time when you make a move so small you're not even sure there was a move and the comm changes by 5-10 degrees!  I think* that all arms are made to within a certain "tolerance," and the cost/labor involved in making arms is not insignificant. If a shop were tossing arms outside of the narrowest range for "perfect," a lot of perfectly good and maybe even race-winning arms would wind up in the garbage.

 

Hi John,

 

I know that you are a hand winder and a damn good one at that! Now, First off in your case I do have a great respect of help, knowlage and opinion. I do want you to know and understand this.

 

Now my question, if a customer calls you and asks you for a 40 degree GP12 arm would you send that customer an arm that reads 30 to 50 degree? That's 10 degree off in either direction.

 

Ben

[Cheater]

Ben,

 

Let me make a suggestion to you.

 

You seem to have a small stock of arms on hand. Take your timing gauge and measure the timing of each of the three slots in the comm. Record your figures so you know what number you get from each slot. Go through all your arms and then do it all again, maybe twice more. And take a hard look at the figures you got.

 

Let us know if you found that you timing gauge is repeatable for multiple readings please. And also if you find arms that have the same timing for all three slots.

 

[Ben Morrow]

As has been pointed out, none of the arm makers have been able to generate the kind of timing accuracy you're wanting. Can it be done? Sure, if people are willing to pay the price it'll cost.

 

Virtually any manufactured item carries a dimensional plus or minus tolerance and it is a given that the smaller tolerance, the more the item costs.

 

Hi Cheater,

 

That's the only post so far that has anything in an honest direction. I can understand this way of thinking. I feel hand wind arms should cost more but also be pretty dang close to what's ordered. On the machine winds although I feel it a shame the machines they use are kinda sad. I guess it's all you can get. The machines can wind nice good-looking winds but fail in the timing dept. "In my eyes anyway"

 

Everyone has an opinion, guess I'm a little too strong on mine.

 

I would just like to let things go and put and end to all the BS. My topic started as a help me do this and has turned into something I'm not proud of.

 

I would like to say if can that Swiss not even reply to my post? Just too negative and seems to start trouble anywhere he posts. I'm asking please stay away and not reply to any post I make. I'm asking this in a nice way! I know your an expert in your eyes but certainly not in mine

 

Greg, I'm sorry for you having to step in this. Please advise if needed.

 

Regards,

 

Ben

[Ben Morrow]

You seem to have a small stock of arms on hand. Take your timing gauge and measure the timing of each of the three slots in the comm. Record your figures so you know what number you get from each slot. Go through all your arms and then do it all again, maybe twice more. And take a hard look at the figures you got.

 
Hi Cheater,

 

I've tried what you're describing and it's part of the reason for help needed in this thread. I'm having trouble understanding why when everything's at 120 degrees, comm tabs and comm slots I cant get matching numbers.  This part was come later on but was sidetrackeded with Mike before I could get that far.

 

Glad you brought this up.
 
Ben

[Cheater]

Ben,

 

Assuming that "everything's at 120 degrees" is simply not correct.

 

Maybe you missed that Mike said in his post #28: "The slots are seldom a perfect 120 degrees apart." 

 

Don't neglect the repeatability of your timing tool. Measure the same arm, all three slots, a few times and see if you get the same figure for the slot every time. I'm betting you won't...

 

And please keep in mind that virtually no arm maker manufacturers the comms they use. In fact, as John H. will tell you, finding anyone to supply comms for the arms he's winding is/was a real struggle.

[Phil Smith]

Pro Slot has been claiming for years that their comm timing is accurate.

Armature timing and Aftermarket timing fixtures

[Ben Morrow]

Cheater,

 

I'll give it a try and report back.

 

Ben

[zipper]

With my similar tool 1 deg difference is normal, must be pretty exact when measuring to get at least that. Exact 120 deg comms may be one of 100 arms... The normal spread on good arms is 2-3 degrees.

 

But when getting a Gr 27 32 deg that measures 27 I'm not happy.

[havlicek]

Hi Ben,

- If someone asks me for a 40 degree arm, I'll try to hit that number... end of story. 

- A spread of anywhere between 30 and 50 degrees would be totally unacceptable. If I asked for a 40 degree arm and got a 30, I'd send it back. 

- If I got a 35 degree arm, I'd be unhappy, but probably try and make up for the difference by dropping or adding a tooth. To me, I think a spread of up to maybe 3 degrees in either direction would be "acceptable"... but... I wouldn't think someone who wanted more accuracy would be necessarily "unreasonable." 2 degrees in either direction is getting pretty darned good IMO.

[jimht]

Given that the comments of those producing arms indicate degree numbers and measurements are approximate...the use of a tilde (~) ahead of the degrees combined with perhaps a +/- wag factor is obviously necessary on every armature header card (and perhaps engraved on the arm itself in case the card is misplaced).

 

Shouldn't raise the overall price more than ~5-20% +/- 5%.

[Ben Morrow]

Hi Ben,

- If someone asks me for a 40 degree arm, I'll try to hit that number... end of story. 

- A spread of anywhere between 30 and 50 degrees would be totally unacceptable. If I asked for a 40 degree arm and got a 30, I'd send it back. 

- If I got a 35 degree arm, I'd be unhappy, but probably try and make up for the difference by dropping or adding a tooth. To me, I think a spread of up to maybe 3 degrees in either direction would be "acceptable"... but... I wouldn't think someone who wanted more accuracy would be necessarily "unreasonable." 2 degrees in either direction is getting pretty darned good IMO.

 

 

Thanks John,

 

@ 2 degrees anyone would be happy or should be after seeing some of the readings I have and many others have I'm sure?

 

Just what I hoped I would hear from you!  A+ Builder in my eyes for sure! 

 

After all this discussion on timming and how close it should be, it's looking like I was being a little tight on the numbers here.

 

"Just an idea here"

It seems if the timming marks on the arm stack were marked after the arm is finished it would be a more accurate, honest  number / reading. Arms are hand scribed or marked and would take no more time to do either way. Plus would be a good close, maybe not perfect, but good honest  reading. Maybe that's asking too much, I just don't know.

 

I really just want to get this thread back on track! Forget all the BS and keep going on with the help of "MOST OTHERS" and teach me the proper way to time and wrap a good close to correct arm.  With Just plain old comms with 3 tabs and 3 slits at close to 120 degrees!  No more CRAZY stuff I've for sure never seen.

 

Greg, I have those readings on 3 arms and I think you'll be surprized. Will post findings after supper..

 

Thanks Guys!

Ben

 

 

 

 

 

 

[brucefl]

I have the shaft hole drilled through a glass mirror (the scale is on the back side) with a dentist's diamond – no play there so far.

whats a dentists diamond?

 

being a dentist im only aware of the dental drill bit being referred to as that.