MikeXray

iTrader: (73)

SMC's packs have excellent voltage as well my 4000 cycles at 7.37AV and are ROAR legal if you need to worry about that kinda thing.

Mike Haynes

iTrader: (2)

Hey John i have one of those scorpian chargers as well, yes it does a good job balancing, but mine also puts in a significant overcharge to 8.54 volts. That would give a pack around 200mah of additional runtime, you may want to check into that.

John Stranahan

iTrader: (27)

Thanks for the posts.

Mike I assume you are reporting on an SMC LIPO. Would it be this one. Your initial number is very good what did you get for capacity. Maybe you can report the data again after about 25 cycles. Thats a number I try to get on each brand of LiPo. I ditch the NiMH before I get that far.

RCracingkid- Mike - I'll check the finish voltage one day. By the slow rate my FMA packs are deteriorating I would not say that my packs are getting an overcharge. Overcharge tends to kill capacity over time. I have had a very long term test with these chargers. What kills capacity is charging at over 1C (5 amps on a 5000 mAH packs). Many manufacturers still say their packs can withstand 2C or even 3C charge rate. They can but it kills capacity much faster. They don't tell you that. Typically though I pull the pack while the charger is blinking medium fast or rapid rather than waiting for a 100% charge. I also have experience with an astroflight charger with auto cell selection. I would not get this. It ruined two partially charged packs.
These old FMA packs still have killer punch in the touring car and wide pan car.

MikeXray

iTrader: (73)

Yes the Lipo 4000, I got 573 sec runtime, I ddin't record the mah, I also use a 6.1v cutoff and 25amp discharge since I run mostly stock and 19t, and I am paranoid about ruining the lipo from over discharge. with the same settings my 4 month old SMC Energ 4600 6 cell pack was 7.41AV and 542 runtime. (5.4v cutoff). I would assume better #s when new, but I didn't have a turbo35 at the time, and don't plan on getting any new 6 cell packs if I can help it.

John Stranahan

iTrader: (27)

Mike-Thanks for the extra detail. That LiPo comes out to 3979 mA-h new. The NiMH is 3763 mA-h which is about what 3 of my 4600 NiMH measured new. I returned these.

BSR Capped Rubber Tires for the Oval
I received Ricks BSR Capped Rubber tires. Thanks Rick. He has a secret advisor or experience apparently as the set is fairly complex. Here are the descriptions. I will try to test these tomorrow. My touring car gets very good and smooth traction on rubber tires on this asphalt. I look forward to this test. The L and R are offsets rather than left and right.
R Blue Front Radial (I need more info to determine the side)
S Blue Front Radial (Standard offset)
S blue Rear Radial (used on right rear)
L blue Narrow Rear (used on left rear)

Also came a similar used set in all pink.

Also note from the pic. The new top plates came in. They have removed the extra hole. This is good for strength. With the top plate off it is easy to feel the tension from the lead wires in this arrangement. It is negligible.

I have just installed the Spektrum capacitor. I had a couple of corner exit glitches which may be caused by low voltage right where the motor has its highest load.

The caps measure 2.480 inch in the rear. I will regear accordingly.

Amp-seconds (A-s) to mA-h for my 5 month old Worley Parsons cell from FMAdirect.com
843 s x 20 A x 1 hr/3600s x 1000mA/1A = 4683 mA-h

John Stranahan

iTrader: (27)

Rubber Caps
I gave the used pink capped rubber tires a short test. First without track treatment. I could drive them but they were a little squirrely on corner exit due to the different left and right rear tires. They may work good on the wide pan with two fat rear tires on the road course untreated.
I treated the track with 4 lbs of sugar. I was hooked up now. I had too aggressive steering. The tires would screech into the corner and stumble on themselves a little. Less dual rate cured this. Now I had some late corner oversteer. I cured this with more left down tweak and a more rearward wing. The car felt pretty good now. The tires roll really well as they are so much harder than foams. They are also heavier which carries good speed through the corner. I felt I should increase rollout .1 or .2 from 3.2 inch/rev. I'll try that tomorrow or Sunday in the race. They are showing promise. I have no times to report yet though. I was using a used set of pink tires that scrubbed in pretty quickly. They look like they wear forever.

GenX10
Turns out the battery trays are identical with the Losi JRXS Type R. I ordered a pair of these for $3 to replace the one I modified for soft packs.

John

John Stranahan

iTrader: (27)

Race Report
The car performed well. It won 3 heats qualified first and won the main. Was I better than last Race. Well no about the same. Here is the blow by blow report.
Last Friday I had treated the track with 4 lbs of sugar. Track temp was 140 F. I had tuned the car to the pink rubber caps and they were hooked up except a gearing problem. Turns out I was overgeared. I had forgotten to reduce the pinion for the overly large tires. They seemed fast and seemed to roll through the corners better. I tried this morning early, but the track was only 90F. Part of it was also shaded and perhaps a bit cooler. The pink caps were not hooked up at all. I just slid around on too hard a tire. I used traction compound. I went back to GRP foams all around, pink all around. Traction was good, but not high. I had reduced the sugar as we had complaints from other drivers of too much traction. Changing the car back right for foams was not a swift put it back just like it was.
I oversteered in the first heat.

I understeered in the second heat from changes to left down tweak and wing. I was within 1 click of dual rate of having the car perfect. I tried to increase my steering in the race with my thumb on the dual rate thumb wheel, but I can't really accomplish that, I spun out due to medium traction conditions. I ran my fastest heat which was compromised by the spin. 53 laps. I also ran my fastest lap. The lap was not as fast as last Race but faster than last weekends practice.

In the third heat the car handled well. I was getting a wiggle toward the inside board from that corner exit oversteer.

I swapped left and right tires for the main (front and back) and added a 1/16 spacer inside the left wheel. This made the car steer toward the outside board too hard. I found myself on the paint a lot early on, but won by good fortune and getting used to the car later in the race. That's too many changes for the main. Swap your tires after heat two so they can scrub in a whole heat before the main.

I had two hits on my rear quarter panel. If you are driving your normal line and you get hit in the rear quarter panel that is a hack even if you have just got your lap back.

John

John Stranahan

iTrader: (27)

Track Test
Air Temp 96F, Track temp 145F, slightly dusty.
I had a new Protoform THD body (Toyota). Ok not real proud of that. I have decided to go back to the road race type of wing. Here are some reasons. Fast laps were not faster with the oval wing, not much slower .02 seconds, but slower. The car gained weight up high. This caused three middle of the straight traction rolls very similar to what the SUV's do when they have a blowout. I would loose a little traction on a difficult spot on the straight. We have some water that comes out there on occasion and removes the sugar. The car would torque steer just a little. I instinctively counter steer after having driven pan cars for a long while now. I found the car on the side. Very odd. Not always the same side. Racers would utter what the ___ was that. Anyway I corrected my driving to eliminate this. But the wing was not faster. It is heavy it is high it has considerable drag from the huge side dams. I put the .3 ounce wing back on. I'll get some more data this weekend. Now I have to say that above 40 mph you appreciate those huge side dams as they give the car straight line stability. We are not going that fast with a 4 cell and 13.5 on flat asphalt.

Nat came by and we tuned a little bit. I had the caster set to 2 degrees right and 2/3 degree left. I could just not drive this smoothly. The dual rate setting was too critical. I had too much turn in. I went to 2 degrees on both sides and the car settled down. Now I had a range of dual rate that was suitable. This is better in my opinion, to have a more rugged setting, that is not so critical. Nat thought the car was rolling too much. We increased spring rate on the front from Red 10 lb/in to Purple 14 lb/in cylindrical.

I increased the axle spacer inside the left rear in two stages to 1/4 inch where it completely cured corner exit weaving to the inside.

Nat reset left down tweak. The car was driving very well. I measured left down tweak at home it was 10.4 ounces with body on on the corner weight scales. This is the excess left rear weight. Ready to race. I am scrubbing less than before. Steering was excellent. Corner exit wiggle is gone. We will see if lap times improve. They should.

John

John Stranahan

iTrader: (27)

Some questions came up by private message.

Gearing
I thought I would discuss rollout here as many guys new to pan cars may be unfamiliar with it. Touring car guys that run rubber tires usually just calculate overall ratio.

Firstly if you run a brushless motor, you need gearing advice from somewhere. The Novak guide in the link is a good starting point. For example if we want to run a stock motor equivalent 17.5 you get a 2.9 inch suggested rollout.
This means the car moves 2.9 inch for each revolution of the motor. Now if you are a gearhead like me this is all you need to know, you whip out your calculator throw pi in at the right place and come up with a pinion spur ratio to buy but there is a little more to it.

http://www.teamnovak.com/tech_info/brushless/br_gearing.html

Gear Pitch
There are two common gear pitches used on pan cars: little delicate teeth (64 pitch), and big rugged teeth (48 pitch) Most of us, outdoors, on a road pan car prefer the big rugged teeth. The little delicate teeth will tend to strip on the first application of the brakes even if by accident. Tiny rocks will get stuck in the tiny spur teeth and ding up the pinion.
On the oval mosts guys tune out all brakes or at least drag brakes. The little teeth do not strip as much and allow finer tuning of gear ratio without pulling the spur off the car. You just pick one or the other (pitch) and stick with it. 64 pitch pinions that are aluminum and hard coated last about 5-6 runs on our outdoor oval. At this point the hard coat is lost, the gear gets white on one side of the teeth, the teeth start to point up and power is lost.
A hardened steel 48 pitch pinion, however, can last years with a stock motor and the bigger teeth.
A gold hard coated steel pinion in 12 tooth will last 20 runs with a 3.5 brushless. A nickel coated steel pinion will last barely 2 runs with this same motor. This is the worst combination for extreme gear wear.

Spur size
Not every size spur will fit your car. 96 tooth 48 pitch (128 tooth 64 pitch) is large and may require grinding parts of the car away to fit. The motor must be able to move far forward. A 84 tooth 64 pitch spur (63 tooth 48 pitch) is small and will usually fit. At some point here the motor starts rubbing the rear axle. Spur gears in between these two extremes will fit without trouble.

Rollout
What is the difference between a 3.00 rollout and a 2.60 rollout"

Rollout is how many inches per motor revolution the car (rear tire) travels. The more inches it travels per motor revolution the taller the gear. The 3.0 rollout is taller than the 2.6 rollout. There are more teeth on the pinion on the 3.0 rollout. The car will accelerate faster with the 2.6 rollout (more like first gear in a car). The car may reach more top speed with the 3.0 rollout (more like 3rd gear in a car) given sufficient distance or motor power.

If you want to duplicate a rollout first measure your tire. Mine is 2.1 inches. multiply by pi, 3.14, to get the tire diameter. Mine is 6.59 inch. Divide this by the rollout and you get your pinion spur ratio. If I divide by 3, I get a 2.19 ratio.

If I am using a 100 tooth 64 pitch spur then divide 100 by 2.19 to get your pinion. You get a huge 45 tooth pinion. The 2.6 rollout gives you a 39 pinion.

To calculate your rollout (Tire Diameter x 3.14)/(Spur/pinion) You can use inches or millimeters.

Here are some more thoughts on rollout. If I were on a hard banked velodrome where lap two could be significantly faster than lap one due to a slow build up of speed then I could use a huge rollout. This would probably be the highest of the rollouts for a given motor. ( I have seen an adaptor to put spur gears on the motor.) If the track is flat asphalt and the car slows down significantly in the corners where lap 1 speeds equal lap 2 speeds then you would not need as much rollout. You need to accelerate better on the straights; there is not such a speed buildup from lap one to lap two. Now where our track sits between these two cases is a matter of debate. I suspect it is more like the second case where you don't need as much rollout.

From a motors view if you could have the motor at maximum power for most of the lap then you should get the most out of it. So where is that. I did some calculations and peak amperage on four cell should be about 45 amps or so. This means peak power is at about 22 amps or so. If we could get the motor to pull 22 amps for the average our performance will probably be better.

Another factor I don't consider is that a higher rollout has the effect of numbing the motor. This lets you corner at the limit without possible disruptions from too much motor torque. I'll have to see.

Pic shows a Nickel Plated Hardened steel pinion after only two runs on a 3.5 powered pan car. Yikes!. It still works but is no longer fast. The rounded tooth form has become knife edged and now slides intead of rolls on the spur teeth. Get the titanium nitride gold steel pinion from Stormer instead. Right pic. This gear is smooth just magnified a lot for a camera experiment.
john

John Stranahan

iTrader: (27)

Flywheel Motor Dyno
The first pic shows Barry's Fantom Facts Machine Dyno. Trinity P2K2 installed for testing. This is a flywheel dyno that operates at 5.00 V. The output is thus well suited to 4 cell racing. The dyno works very similar to a Dynojet Full Size Car Dyno where you put the driving wheels on a heavy cylinder shaped wheel. You put the car in 3rd and rev the full range of the motor. The dyno then calculates torque and Horsepower from the acceleration of the wheel and can plot these as a function of RPM.

We are getting this thing in operation in several stages. Barry found a newer motor builders software that allowed the use of a more modern computer. The original floppy disk software failed. Unfortunately at this time I can only print motor labels which you can see in photo 2 and may have seen on a variety of brushed motors. The key indicator here is power in Watts. 746 Watts=1 HP. If you gear the motor correctly, a more powerful motor (more Watts) should complete the race faster.

I can't do a complete motor curve yet, but I can do a very interesting test once I adapt the dyno to brushless. There are 3 rotors available for our 13.5, one epoxy, and two sintered of different diameters. So that will be the first test. Which gives more power.
If someone can help me out with a link or loan of software that will let me print a motor curve that would be super. I may buy the $75 package from Decco software, but I would rather not at this time. An e-mail to Decco Software was not particularly helpful in reviving this machine.

A second run yielded 49 Watts at 8.2K. Very good precision and an understandable increase for a motor that has been sitting for 3-5 years.

John

John Stranahan

iTrader: (27)

The pic shows the modifications made to the dyno. A receiver from the touring car receives a full throttle signal from my transmitter and finger. The motor is run. I get a good curve and a good number. 58 Watts at 9.1 kRPM. This means the brushless is about 18% more powerful than the stock motor I tested in the previous post. The 13.5 is called a Super Stock. Now the bad news. I had 3 rotors and two cans to test. Each one yielded the identical 58 Watts at 9.1k RPM. Max RPM was the same to 1 RPM. As if a robot was limiting the spin up of the flywheel. And in fact there is a robot running the motor, the sphere speed control. It is possible that a punch setting or just a programming limitation is limiting motor acceleration. The printouts are not identical and include a spurios efficiency reading so I think the Fantom is working OK. The speed control is precisely controlling acceleration no matter what the rotor. Anyway thats my current theory. Time to pull out the LRP manual.

I maxed the punch control out to 6. No improvement. I still get the same numbers.

John Stranahan

iTrader: (27)

I found a combination that gave me reasonable numbers from the dyno. I had one problem, the 100% throttle was not being reached. I adjusted the tranmitter and made sure I got the blue full throttle light. On the suggested power (12 V battery), I got bigger numbers but still always the same. I suspect that a feature of the LRP that controls punch on first start might be to blame. I hooked the speed control up directly to a charged 4-cell pack gave the motor a few slow warmup gooses of the throttle, Reset the Fantom software to do a full 5 second run. Then I hit motor run and simultaneously pressed full throttle. Since this dyno measures power from instantaneous acceleration of the flywheel any error in hitting the throttle just right on time will not matter to these maximum power numbers. I got variable data now which is more likely to be correct. The 12V to 5 volt part of the Fantom was unused.

Small sintered rotor 66, 69 ,66 Watts for three tests averaging 67 W average 9.6 kRPM

Fat tuner Rotor 64,62,65 Watts for three tests averaging 63.6 W average 8.9 kRPM

So what does that tell me. I have been using the fat tuner rotor in error thinking it was more powerful. They don't tell you jack about it. You can use the RPM average to adjust your gearing to suit if you do a rotor swap.

I have been using 3.2 inch rollout with the fat rotor. I should adjust this with the RPM ratio I measured.

3.2inch/rev x 8.9kRPM/9.6kRPM = 3.00 inch/revolution

The system sits there for a while if you have bright ideas for a test. I won't be running the 3.5 on the machine as the RPM reached are excessive. You will have to take their word that these (and the LRP 3.0) are putting out about 746 W or 1 H.P.

I still want to get a motor curve to find peak amperage and amperage at peak power.

John

Quante

iTrader: (6)

I'd find it very interesting to see a Delta vs Star dyno-graph...
But then you'd have to have access to 2 motors that are pretty much the same specs but one with delta and one with star winds.

If there's any chance of you trying this, than it would be great!

rcbarrmeister

John,

Below is how Steve "the Rocket Man" Miller suggested using the dyno for brushless on another site.

We use the dyno, a receiver and a speedo. Hook the motor to speedo and then use the red and black wires to hook up speedo to dyno ..Now take your radio and pull full trigger and hit the dyno button ..... It works the same everytime and no need to keep charging the batts ....

Were you able to get the DOS software working?

John Stranahan

iTrader: (27)

Barry
I had it hooked up just that way. It gave me absolutely identical results each time
"It works the same everytime"
that I believe were limited by the punch control on the LRP. The reading were thus in error. That is why I changed to a more manual setup. The GTB's don't have this punch control. It might be a better speed control for this setup.

Quante
First, I assume you can get both winds in a sensored motor. I won't run any more unsensored motors as they have many drivability issues. If you have both winds ship them to me and I will give them a test and send them back. I do not have both. I also do not have a sensorless speed control.

John