John Stranahan

iTrader: (27)

Here are a couple of more Motor Spring testers that I have come accross on the web.

This is a digital device from Eagle Models. They also sell a digital device for coil springs like shock springs and coiled motor springs.

http://eaglemodel.com/en-net/en-menu.html
go to category, motor, spring dyno.

Niftech also sells a device that uses a standard gram pull scale. Here is a link to a (poor) image of the device.

http://www.niftech.com/pix/cat/4725.jpg

Here is a link to the Niftech catalog page.
The listing and description are near the bottom of this page.

http://www.niftech.com/catalog/index...ode=4000series

Niftech also has this fixture that lets you use a balance to measure a number of kinds of springs. This is similar to what I do when at home.
http://www.niftech.com/pix/cat/4730.jpg

I don't have these devices to give you a report on their quality.

BATT_MAN

John,

After I saw your spring gauge I decided to take your idea a step further

I took an off theshelf 500g scale and took it apart, just kept the string gauge and electronics. I am machining a new cvase with a spring post to attach the spring and put the pressure against the gauge.

Its working just fine. Once I finish the project I will post it.

The scale costs under $15, therest of the necessary equipment should be under $10. So for $25 I have a very accurate gauge that will give me the spring compression in grams and ounces...

Thanks for the idea John.

Isaac

Roedor

Hello, I am new on this, can anyone tell me which "numbers" are good with 4.8 volts for a modify motor?

Thank you and happy new year.

eg

iTrader: (1)

Hello All,

Great discussion... Here is a chart that I created to simplify things for me. Please feel free to comment on the chart. I have this in excel if anyone needs it.

Note: Remove the decimal point in the RMP value. I just did this because the RPM numbers were to large. Exe 151.25 is equal to 15,125 RPM.

Thanks,

John Stranahan

iTrader: (27)

I found a Trinity Spring tension gauge on the wall at Mikes. Here is a conversion to ounces. Good tensions for stock motors are going to be between 1.75 and 2.5 on the gauge. The gauge really needs a softer spring. I pushed it on the scale with a fixed support to get numbers. Took two sets of readings. Precision is about .2-.3 ounces. Now if that full page ad up above was just a bit smaller we would not have to scroll this thread.

Trinity Spring Tension Gauge

Trinity Units, Ounces
1, 6.3
1.25, 7.1
1.5, 7.9
1.75, 8.7
2, 9.5
2.25, 10.3
2.5, 11.0
2.75, 11.8
3, 12.6
3.25, 13.4
3.75, 15.0
4, 15.8
4.25, 16.5
4.5, 17.3
4.75, 18.1

John Stranahan

iTrader: (27)

I had some good luck tuning a couple of Trinity Cobalt 10 x 1 Mod motors (one flat wire, one round wire) using the Trinity spring tension gauge that I described in my previous post. Here is a link to a report by Cristian Tabush on the motors performance as well as his FTTC4 performance.

http://www.rctech.net/forum/showthre...ed#post2174057

Now that I have some time on the little instrument I can clarify a few issues. When you push on the spring with the device while the spring is installed on the motor you are at a point on the spring that gives you less mechanical leverage than the little spring stop on the top of the brush hood. This means that the numbers that I posted above will be higher than the force applied to the brush, about 3 ounces higher. So subtract 3 ounces from the measured ounces that the tool applies to the spring for the Trinity purple spring. I may come up with a more accurate correction formula later. It will probably be a percentage correction or better, a new little table of values.

The tool was easy to read on this heavier spring. The reading was in the middle of the scale which is always good. The Cobalt 10 x1 round wire motor was ballistic when I tuned the spring to the number 4 on the Trinity gauge. This is slightly more tension than the motor had as delivered. Stock silver Octagon brushes.

I also should report that I removed the two heatsinks from the brush hoods. This left two nice huge holes for air to enter and depart the comm area. I think that large holes are much more efficient at cooling the comm than heatsinks. Cooling the brush is probably not so important on these silver brushes.

SA_Racer

Now why do motors that draw low amps not perform on my Dyno. Don’t get me wrong, I don’t believe just because a motor draws 7-8 amps during run in it will be a good motor, I believe its more likely to be a good motor. But what I have noticed is that none of the motors that draw low amps ever perform.

Further to this I have tested different armatures in the same can/hood combo and find that even though the same can/hood combo works great for one armature, it doesn’t work for another.

Here is a test I did with 4 motors. I took one of my bets monster motors,

Cut and Measured the com, installed new brushes and run it in at 2v for 300 seconds
Ave amp draw during run in was 8 amps. On the dyno and on the track this motor was fast.

I then took 3 more armatures, cut the com to the exact size as the first motor and installed (1 at a time) these arms into the same can/endbell that I used for my best motor.

All if these were pulling around 3-4 amps during run in and showed really bad numbers on the dyno and didn’t perform on the track either.

I inspected all the arms and with the naked eye I couldn’t see any major difference between them, in fact the good motor doesn’t look like its wound any better than the bad motors, so what makes a good arm good?

Do other people also have this problem when tuning their stockers or am I just doing something wrong?

How come the motor tuners always manage to tune all their motors the same way and still get good numbers from these motors?

Hyper1

That's because motor tuners have hundreds of motors to go through and get the ones that are good and junk the rest,they don't get good #'s on all their motors,there are manufacturing differences that you just can't overcome on some motors,unfortunatley it's just one of those things that we have to deal with,when I get a motor that just won't run no matter what,I usually just chunk it and get another one,or turn it into a practice motor,I've probably got two or more practice motors for every good race motor.

BigDaddyT

Agreed. I think that's the main advantage that tuners offer to the market. A credible motor tuner will ditch any motors that really underperform. It's not good for their brand reputation to have inconsistent motors, so the oddballs go into the junker. The increased price on the tuned motors isn't just to cover the tuning - it also covers the cost of motors that don't perform well enough to ship. You pay a bit extra, but should always get a decent motor.

From there, you really just end up with the normal manufacturing variance found in any sort of automated process. Machine-wound motors will always have some inherent differences even if they are not visually obvious. Usually though, it shouldn't be a huge difference - everyone has their own range, but if a motor is more than a few percent out of whack, it's usually worth taking a second look at it.

dgullickson

iTrader: (45)

Most of our Motors that dont meet a certain criteria will be sold to local Novices as what we call a "Sport" Motor.. I think its agreat way t osave the new comers money when they really dont need the best of the best..

John Stranahan

iTrader: (27)

Stock motor amp draw at no load is pretty much controlled by the spring tension. More tension more no load amps. When I was running stock motors, I always set them up with measured springs and fully broken in brushes before I did any testing. Then the variance was actually quite small. Never more than 2% or so. If you are getting 3 -4 amps difference at no load I suspect that springs on the low amp motor have lost their tension. I would be surprised if you had that much variance changing cans if you use the exact same pair of springs with fully broken in brushes. If you do get the high variance, there is a small chance that the windings are not in good contact with the comm tabs on the weak motor from an incomplete spot weld. This problem can be be fixed by the manufacturer. Get a spring tension gauge if you don't have one already.

SA_Racer

Based on what you guys are telling me it sounds like I’m definitely doing something wrong with these motors. The spring tension is the same during all tests and changing to stiffer springs doesn’t seem to have any major improvement on these motors (using the trinity spring gauge).

funny thing is that all the motors that look bad on my dyno come from different motor tuners with good reputations. The good motors are motors that I bought off the shelf at my LHS.

my good motors tend to be about 5-8% better than the best of my bad motors, and the good ones are real screamers. When I run the weaker motors it shows

at some stage I thought maybe my com lathe isn’t up to the job, but then all my cuts should be bad, still the good motors are always good and the bad ones aren’t getting any better. I’m using a Hudy com lathe with a diamond tip, tip looks good under a magnifying glass. I also tried a trinity diamond tip.

I will just have to figure out that these weaker motors have in common

dgullickson

iTrader: (45)

How many motors?

SA_Racer

I have 11 Stockers
2 Are really awesome (probably the fastest 2 motors at my home track)
3 close to the first two, Great for club racing.
The remaining six are no good.

So I guess you could say for every good motor I have, there is also a bad one