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Old 06-24-2007, 09:57 PM   #1516
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John,

I have tried 40% brake with LRP 1 star motor, just like you said, it was almost nonexistence. With 5700, the brake is hard enough to cause major spun at the end of the straight line. That's why I had to tune it down. I can now entered hairpin nicely if compared to my Spheres and GTBs, gosh I love the Mamba max.
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Old 06-24-2007, 10:24 PM   #1517
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Say we adjust the Novak GTB 3.5 to 70 percent brakes (at the radio) and the Mamba to the same (at the radio (software at 100%)). Same Motor. Just hold the car in your hand spin the tires up a bit and apply the brakes. You will swear that the Mamba is going to rip the teeth out of the spur it is so rough. It is not braking faster just rougher, almost as if every other pole is skipped and there is a power reverse added in between. The GTB will make the tires slow to a nice smooth fast stop. Our pan cars do not like any shock to the rear tires.

Now let's say we adjust both controller to 50% at the radio. I found that the deceleration rate is about the same. Very likely however the Mamba will lock up the axle and cause a spin. The GTB will brake very smoothly at this level which is not very high.

So what I do with both controllers is that I drive with the radio set to adjust the brake endpoint. I setup the controller with 100% brakes. I turn it down in practice at the radio until I get no spins braking into the hairpin. Traction will pick up during a race and you will have a little safety. Typically the Mamba ends up at 40% or below. Very little additional brakes over my dragbrake. Rarely will the GTB need less than a 60% setting to prevent spins. My LRP competition brakes used to work very similar to the GTB brakes.

My rear suspension may help braking as there is lots of droop available at the back and it is more supple maintaining even tire loading.

Brushless motors do not have the potential to brake a touring car as fast as a brushed motor. For our pan cars they have a little excess of brakes.
John

Last edited by John Stranahan; 06-25-2007 at 01:49 AM.
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Old 06-24-2007, 10:33 PM   #1518
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John,

interesting! you mentioned about the mamba max drag brake. With around 4 years of toying around with novak and lrp brushless esc, I have some mindset change to make when switching to mamba max.

I noticed for Mamba max that 20% or 30% of drag brake may not mean 20% of the total brake as what we put in for the total brake box.

For LRP and Novak, the initial brake is determined by the amount of drag brake we set.

I made some testing with 20% drag brake and 30% total brake. If I let go the throttle after a full throttle, the motor will slow down and takes some time to reach full stop. However, if I hit a full brake the motor will stop to stand still.

This makes me wonder on what does it mean by 20% drag brake?
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Old 06-24-2007, 10:37 PM   #1519
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Azmio-I experienced this myself. I found the brakes almost useless if I programmed in less than 50% brakes. That is why now I just leave the Mamba at 100%. My drag brake works right, and I can turn down maximum brake only at the radio.
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Old 06-25-2007, 04:17 PM   #1520
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Binding the Small Spektrum Pro Receiver with Failsafe
I have answered my own question. I thought I would post the results. When binding the small receiver the jumper loop goes into port B of the receiver. This is where I erred. I tried two other ports. The car is turned on, the amber LED blinks rapidly. Turn on radio with partial brakes and spektrum button pushed. It would be nice to have a third hand as usual. When both lights quit blinking, you are done. Success. Thanks Azmio. This will reduce my stress greatly on the next speed run.

Pic :Note binding loop on small receiver. Must go into port B. Awaiting final install.

Speed Run
OK here are my personal rules 7.4 Volts, wide pan car, any body or aerodynamic mod. Any motor. Anything that I already have in other words. I have several old bodies to cut up. Last session, on the parking lot, I had some blowovers. Our secondary parking lot area is graded somewhat like a drive in movie to create good drainage. This means there are gentle humps peaked between the row of cars and lower in the drive areas. My car would fly at speed when it reached the peak of the humps (alias launching areas). Nick and I test the path with my car first.
We changed to a shortened primary area which is smoother. The rest of the primary area was a little wet. I was able to obtain top speed. One time beyond the radar gun the car launched. It might have been a pebble. Many times it did not. We did walk the course to remove pebles. I swept just a little. If I want to go faster I am going to need more front downforce and less rear downforce. So I cut the entire spoiler off a Peugeot body. Left the side dams in place. Constructed a half belly pan from the nose to the middle of the car. It will have some upward rake going towards the back and may produce some ground effects. I am removing the soft dam. The main purpose of the belly pan is to keep small lifts of the nose from jetting air up into the body shell at the front gap. Who knows. I have two small wings that I can attach near the rear body post area. I will gear my 4.5R to the moon as I think it is the more powerful motor in my stable at present. Measured speed so far is 53 mph with the 3.5R with settings and gearing for the track. It did go faster in a previous test with the 4.5R geared 4 pinion teeth higher than normal, but we had no radar at that point. The rear of the body is 3 holes lower than normal. The front seam is taped. I have some Nylon tape to reinforce the front fenders coming. Front ride height will be higher.
John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-speed-run-trim-resized.jpg   Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-speed-run-b-resized.jpg  

Last edited by John Stranahan; 06-26-2007 at 03:27 PM.
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Old 06-25-2007, 07:16 PM   #1521
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Here is pic of my makeshift wind tests. I tested the high speed body with wing and without the low little black wing. Wind speed was 14 mph. Scales were zeroed with fan off and car on. Positive here is a force downward or down force.

High Speed Body (Peugeot)NO WING or Spoiler (pictured in my previous post and below)
Front Downforce +.4 to .5 oz, Rear Down Force -.1 to -.2 oz(not good at the back, I have a little lift.)

Small Black HPI wing
Front Downforce +.4 to +.6 oz, Rear Down Force +.2 oz (much better at the back. I don't need a lot but I need some
downforce back there.

The motor cog action against the magnet in the motor was enough to hold the car still. This indicates a low drag. My square aluminum bars needed a heavy iron bar to resist the wind. This shielded the front scale and prevented uplift of the flat plate.

A moving roadway may inprove these numbers with ground effects. More front downforce would be OK.

Much Testing on the McAllister Nissan body that I ran in the GT trim (with spoiler and wing) showed that this is a very good place for the wing to keep the car planted. I can move it around higher or lower, forward or back with the little HPI pedestals it came with. I know its ugly there. I do have a clear one.

High Speed Body with small black wing with the front elevated to 1/2 inch on a spacer.
Like after a bump
Front Downforce +.5 Rear downforce +.2 to.3 This is little changed from level. I was hoping the belly pan would do this.


Tests on Standard Body

Standard Toyota GT1 Body with soft dam and 2 inch Spoiler chord.

Front Downforce +.1 to +.2 oz, Rear Downforce 1.4 oz. (The front downforce is an order of magnitude less than the rear.)

Standard Toyota GT1 body with belly pan and Soft Dam
Front Downforce .4 !!!, Rear downforce 1.9 (Both of these numbers are too much higher to be just a coincidence. This should be worth a test on the track.)

As above but Lose the soft dam
Front DownForce .4 oz (not as steady). Rear downforce mostly 1.9 swinging as high as 2.6 (There was more rear downforce.)(Note that my rear lower pod plate sticks down and can catch some air.)

Raise the standard body front up on a spacer with no belly pan with soft Dam
Front DownForce 0 to -.2 !!, Rear 1.9 oz. This low Front number seems to cause the blowovers. The belly pan seems to prevent this lowering of front downforce as well as increases front downforce by a factor of 2 to 3! Hmmm. Certainly worth a road test. I was rained out today.

Toyota GT1 Body with Spoiler Vents and Without
I took the GT1 Body with the two holes cut in the spoiler (with body pan) and then put a strip of tape over the two holes in the spoiler. Downforce at the rear increased from 1.9 oz to a steady 2.9 oz. I should be able to feel this change on the track, but I never have run this body without holes. This seems to be counter to conventional wisdom like a lot of things in RC. These results were very clear. I don't expect that the Peugeot body is different in this regard as the two are very similar.

John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-wind-tunnel.jpg  

Last edited by John Stranahan; 06-26-2007 at 03:31 PM.
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Old 06-25-2007, 09:18 PM   #1522
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Thats cool John. Your test is like the windtunnel testing I did in college on a few inverted airfoil designs.








This is what 80mph does to a lexan wing. It almost touches the trunk of the body.







Here is a link to my full design report in PDF format.
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Old 06-25-2007, 10:08 PM   #1523
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Quote:
Originally Posted by John Stranahan View Post
Adam-The question is answered. That is just another dark blue charger. I thought the power supplies fed your system from the left just off the picture. But they must connect between the dark blue charger and the red chargers.

DrewDC90-Good luck with your car. It looks like it might not be an Associated car at all as it has Trinity on the Chassis. Maybe a Trinity Switchblade. Interesting front suspension, similar to a newly released car that Mathijs posted not to long ago.
John
I know it's old but I just ran across it...Anyway that is an Associated RC10L chassis but it has the Trinity EV10 front suspension for it. Trinity made a version that would bolt up to the RC10L front suspension holes.
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Old 06-25-2007, 11:41 PM   #1524
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inspGdgt- Thanks. I think you caught that one already in a previous post.

Now here is the question. Just how much downforce are we dealing with on the oval and with the 1/10 pan car set up for a Road course? I don't have a complete data set, so I made the following plot from Nicks Data and My data. I frankly expected a curve upward squared or even cubed with speed. Nicks data, shows a gentle upward curve. Only .9 lbs or so is generated by the oval car spoiler at 50 mph. My data is at lower speeds (I have a 3 speed fan) and it shows the upward curvature I expected. If I extrapolate mine unreasonably far beyond my numbers I end up with about 1.8 lbs at 50 mph. This is backed up by observation of the car at the end of the straight. It is hard on the bump stops or the chassis is dragging at the back a little without bump stops. This requires about 2 lbs of force on the scale. We are not dealing with huge forces, but large in comparison to the weight of the car.

The two curves have similar shape but not real similar. There is probably more flex in Nicks car that is causing the disimilarity. My spoiler is .040 Lexan and does not flex much at the lower speeds I tested it and run it.
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-spoiler-downforce.jpg  

Last edited by John Stranahan; 06-26-2007 at 10:23 AM.
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Old 06-26-2007, 05:13 AM   #1525
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John, I would like to commend you for your valuable and informative postings on this thread. This thread has the most technical information explained in a manner that can be understood without the use of a referance manual. I really enjoy your detailed runs with your car and your encouragement to others. My son has been so impressed with your continuous improvement of your pan car and its increasing speed he has searched out and bought a car. Its actually older than him. Even though he has improved his touring car driving he gets more enjoyment from tinkering round with the pan car.
Well done. Was really impressed with your HOME MADE wind tunnel and data measuring

Drews dad Tom
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Old 06-26-2007, 09:31 PM   #1526
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Tom-Thanks. Now If I had a big carboard box I could make a tapered section and boost my air speed and improve turbulence.

High Speed Body Continued (Bending Lexan)

I made a light weight spoiler for the back of the high speed body out of .020 Lexan. This will let the spoiler collapse at speed but allow it to add some rear traction up to about 50 mph. I have a heat gun that I have used to bend this stuff before with poor results. This time I clamped an Aluminum 1/4 inch thick plate to the Lexan to block the heat from getting to the edge to prevent wrinkles. I used the weight of the metal to add a gentle force. It came out with a nice smooth curve and no wrinkles.

This body should have a very low coefficient of Drag and about 1/2 the frontal cross-section of the stock body. This should help it go faster. I also put bigger side dams to help with straight line stability. The spoler is placed like the Nissan NPT 90 GTP body but with a low wing that existed on some of the full size cars. It will help extract air from under the car with two fender vents and because the lower surface is gently curved. Hopefully I wont need the ugly little forward wing.

I used some of my now identified I.R.S white thin foam doublestick tape on the roll in the picture in a previous recent post to attach the original side dams to the body. If you do a neat job here it provides a white accent. Place it on over size. Cut the top of the tape off with scissors. Push the lower part of the tape into the fender groove with a finger nail to mark it. Cut along the top curve and tear off the excess below the fender curve at the cut line. I then added bigger dams with the original screws. This foam stiffened the side dams side to side a lot. Some guys use shoogoo here to glue on the side dams. I could not do a satisfactorily neat job this way.
John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-high-speed-body-resized.jpg  

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Old 06-26-2007, 10:29 PM   #1527
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JOhn, for ultimate high speed running have a look at this body:
http://www.customworksrc.com/Product...001-1057798354
It's designed for wide 10th pancars.
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Old 06-26-2007, 10:41 PM   #1528
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Mathijs-Thanks for the link.
That body has the benefit of a tiny cab, but the spoiler and wedge are huge. I would get too much downforce and drag. I was trying to reduce both rear downforce and drag with the trim I made. It looks good so far. I might test it tomorrow. The Camaro body there looks good. How do you tell what size car they fit.

Lets say I can reach 80 mph. The stock GT1 body that I race would have 4.5 lbs of rear downforce if I extrapolate my data some more. I think that is way more than I need. I am happy with a 1 lb.
John

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Old 06-27-2007, 02:13 AM   #1529
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I have increased my windmachine speed to about 16.0 mph. Its not a tunnel yet but I cut up a box to make a tapered section. I was moving the Kestrel wind speed meter (anemometer) around the car at full flow. Here is an interesting tid bit. I have my body with no spoiler at present. The spoiler was causing front end lift. I put the meter just above the rear of the body. I lowered the meter below the body in the center of the car and you could see the impeller stop and then reverse directions showing a 1.2 mph wind going underneath the body, spoiling the vacuum as I had hypothesized previously. I don't know where that air exits yet but it is not up high. That is why I don't like to cut the bodies out so high in the back. I had no soft dam so I was expecting some flow out up there.

Air speed at the sides of the car was increased 1-2 mph. Airspeed between the axles on top of the car was reduced 1 mph. My wing at the top of the body posts was barely doing anything. It needs to go higher, but not so high it levers the front wheels upwards from drag.
John

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Old 06-27-2007, 07:44 AM   #1530
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John, your idea about a collapsing rear wing rang a bell. Did you ever run slot cars? Remember their wing/air dam system? They had a stiff piece of lexan stapled to the front end to keep air from getting under the body, side dams that ran the length of the body. They also had a rear dam that was bent into something like a scoop. At speed the side dams would collapse and the rear dam would straighten out. Group 7 (open class) cars could get around a Blue King 155' track in less than 4 seconds! Don
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