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Old 05-23-2008, 10:24 AM   #31
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That small gear only has 8 holes. In pro stock it is actually an advantage to have less weight here. In onroad mod I use a larger gear with the full compliment of 12 balls.
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Old 05-23-2008, 01:44 PM   #32
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I'm not sure how it is in oval so this might be a dumb question but do the short 12 guage wires restrict/affect the pod to chassis movement?
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Old 05-23-2008, 02:23 PM   #33
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I asked about 12 gauge use at the nats. It was very common in 13.5 class. My wires are short but they have a nice curl to them which makes them quite flexible. It also helps if they don't touch each other and create friction. The deans wire being a high number of strands also helps here. They don't feel like they are inhibiting the pod rotation much. If they did add some spring or resistance it is of a spring like nature and I can reduce the side spring tension to compensate. I don't think I will have to. I do have a full set of side springs and center shock springs coming for the car.

Left Hub Clamping Screws
Note also in this pic the left hand hub clamping screw. It must be steel. Use blue locktite on it or you will lose the left wheel on the track on occasion. Tighten the crap out of these.

Wheel Lugs
I use four short 5/16 inch aluminum screws that just reach the back of the threads for low rotating mass. Some use two, but I found my wheels more warped after a couple of runs this way. I am back to four Aluminum screws. Tighten only very snug.

John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-battle-axe-lead-wire-curl-resized.jpg  

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Old 05-23-2008, 03:09 PM   #34
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I added text above.

Strut Front End
If you have an associated style strut front end, there is no doubt that it will profit from some handwork to make it smooth along its entire travel. The procedure is well described here with plenty of good diagrams.

http://www.swiftracingproducts.com/Page.cfm?InfoID=5192

Now the goal is to remove the spring, push the suspension up by the kingpin snap ring all the way, and then have it drop by gravity alone. Now put the spring on and push it up again and feel how smooth it is after you have completed the procedure. I can do this last push test now, and by feel tell if somebodies car has too much front end friction (stiction). When you get it smooth you will be rewarded by usable front end traction like never before.

CRC Pro Strut front end
This front end is a little different. The steering block now extends up to a pivot ball similar to what is used for Nitro 1/10 and 1/8 scale car. There is an adjustment retainer or ring that can be used to give the ball just the slightest amount of play.
Remove the spring. Push on the kingpin and feel for gummy friction or drag. There should be little. The suspension should drop back down by gravity alone. This one did not. There was extra friction at the kingpin to the lower pivot ball which is the standard Associated type of pivot ball. The pin was well polished as advertized but the hole in the ball was slightly undersize causing the drag. I polished the pin some more until it would drop free (I removed maybe 1 or 2 tenthousandths inch off the diameter of the pin.). Chuck about 1/8 inch of the snap ring end of the kingpin in the drill chuck of the dremmel and polish the remaing part of the kingpin with fine sandpaper. (I also have a new kingpin and teflon coated pivot ball that may also solve this problem.)

Note in the photo that the upper arm is supporting itself up high wihout the kingpin. This is not good. I will remove the upper A-arm hinge pin and remove just enogh material from the arm pivot end to make it drop free. The pin was tight in the A-arm pivot although the pin was nice and smooth. I spun an undersize drill bit at medium speed in the dremmel and opened up the A-arm pivot until the pin would rotate easy by hand. Now that upper arms drops free with gravity.

Also note in the photo that tiny brass 4-40 set screw. It let's you screw in your kingpin assembly by hand and then tighten the screw when you have removed vertical play. I ordered a couple of spare set screws. As delivered the car had a lot of preload. This makes it act more stiffly sprung than without preload which is my standard.

am going to try fairly soft blue front cylindrical springs from windtunnel racing first. I am using thin blue spring buckets which will give you more clearance at the wheel when you remove all the play.

I sanded the bottom of the kingpins which are the large 1/10 scale size on the bottom to have a little more clearance with the wheel rim with the pin set for 0 preload on the windtunnel springs. There is still enough allen socket left to adjust the pin and enough lip left to support the E-clip adequately.


On the lower arm you will see an additional screw that lets you tighten or loosen the play of the pivot ball in the arm.

when I push the front end down, it feels smooth and soft like the back now. The aluminum teflon coated lower balls are in.

Note the assembly should have no upper spring bucket. Progressive spring pointy side up or cylindrical spring.

John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-front-suspension-mods-004-resized.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-crc-battle-axe-front-suspension-resized.jpg  

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Old 05-23-2008, 08:06 PM   #35
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Side to Side Balance

On a road car we want the side to side balance to be equal. You use a setup similar to that in the photo with two scales and two beams and try to make them both read the same. More detail on road cars here on the TC5 tips and tricks thread.

On the oval we take advange of a unique property of rubber and the mechanics of weight transfer to get a little more cornering capability turning left at the expense of cornering right.

The property of rubber is this. Rubber is more efficient at developing cornering g's the more lightly it is loaded. Thus the way to have two tires on one axle (one left and one right tire) have the highest cornering capability as a pair is to have them carry equal weight.

The dynamics of weight transfer is this. The higher the cornering power, the heavier the car, the higher the car, the more narrow the car, the more weight is transfered to the right on the oval. When this weight transfers right it kills the efficiency of the right hand tires to some extent. The axle has poorer cornering power every time there is lateral weight transfer on an axle.

So what we do, to take advantage of these two situations, is preload the left side of the oval car. When weight transfers right the tires approach that happy 50-50 weight distrubution on the pair. Efficiency remains high. Cornering is good but only to the left.

I have seen setup guides that suggest a 12 ounce left preload on the oval 1/10 scale pan car. I made some small movements of the only things in the car that can be moved to bump my left total to 12.1 ounces left. I moved the receiver back and left. I moved the transponder left. I also can move that big Novak capacitor back and left on top of the speed control if I want more weight back.

Front to back weight balance
Front to back weight balance is measured with the same setup. Just put the front tires on one beam and the rear tires on the other. This car has a 5.6 ounce excess in the rear. This is less than my other car had. We'll see. The optimum position of front to rear weight is a complex function of front and rear tire width (contact patch size), Front and rear compounds, and motor power. So one thing you can do is try and match the front to rear balance to the tires and motor on the car or you can do the opposite and set the car up to drive well on the front and rear balance that you have. I can move my weight only a little due to the fixed nature of the battery tray. I can move it one cell forward, but previous experience tells me I am going the wrong way.

If you are driving mod pan forward traction is at a premium. I put lots of weight back. As one author said, "you can't put too much weight on the back of a two wheel drive". Of course he is talking about a powerful full size car. If the motor is detuned like in stock or superstock then we can concentrate on improving cornering speed at the expense of some forward traction. Maybe move the weight a little more forward for road superstock.

Plastic Body Posts
I replaced 5 aluminum body posts with 6 plastic ones. An extra supports the center of the bumper. I lost 2 ounces. I am happy this BSR blue foam bumper will survive and protect the graphite of the car because of the way that it is supported by the 3 body posts. I will test the CRC Battle Axe posts eventually. They are plastic but use a screw to put on the body. That really looks neat.

Black strapping tape from lefthander RC $6.00 instead of $20.
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-side-side-balance-003-resized.jpg  

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Old 05-23-2008, 08:41 PM   #36
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Old 05-23-2008, 09:41 PM   #37
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Well thanks. Just passing time till I die and if some race car science passes through to you that would be nice.

Here is the car ready to race
The Aluminum pivot balls did not fit the kingpins. Both are a little undersized, but the pivot balls are smaller on the ID than the kingpin OD.

I have a full set of Windtunnel center and side springs for testing.

I can move the motor over left by two full spacers if I need to tighten the rear.

It should be ballistic. Mike D is going to cry!

Second pic is the fit of that BSR blue bumper. It touches the body on the top front corner. My undercar aerodynamics should be improved.

John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-ready-race-004-resized.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-bsr-front-foam-bumper-002-resized.jpg  

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Old 05-23-2008, 11:15 PM   #38
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Quote:
Originally Posted by John Stranahan View Post
Well thanks. Just passing time till I die and if some race car science passes through that would be nice.

Here is the car ready to race.
The Aluminum pivot balls did not fit the kingpins. Both are a little undersized, but the pivot balls are smaller on the ID than the kingpin OD.

I have a full set of Windtunnel center and side springs for testing.

I can move the motor over left by two full spacers if I need to tighten the rear.

It should be ballistic. Mike D is going to cry!

Second pic is the fit of that BSR blue bumper. It touches the body on the top front corner. My undercar aerodynamics should be improved.

John

Hi John,

What body is that?

Have fun tommrow!!!!!!!!!!!!

Rick
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Old 05-23-2008, 11:25 PM   #39
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Thats is a Monte Carlo HD lightweight from Protoform. The guys at my track prefer the HD charger that you included. I have a charger ready with similar paint. I like them both. This one seems like it has less front and rear overhang and is maybe a little more maneuverable in traffic at the expense of some all out downforce. Not really any lighter except maybe .1-.2 ounces. I purchased it to be lighter.
Will do.
John

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Old 05-24-2008, 09:55 AM   #40
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Bump Steer
Bump Steer is when the wheel goes up in bump from either a bump or chassis roll, the wheel changes steering direction by itself. Bump steer is easy to check. Hold the car in your hands with the wheels straight forward. On this associated style pro strut front end push up on the front of the upper A-arm with your finger all the way to the stop. View the wheel carefully. If it is changing directions then you have bump steer. If it steers out as the tire goes up in bump you have bump toe out. If it steers in you have bump toe in. Bump toe in can cause the car to oversteer as it rolls in the corner. I avoid it. A little bump toe out is OK.
The car had some bump toe in. The inner steering link pivots were mounted in the middle outer holes of the servo saver. I moved them down one hole and at the same time replaced the aluminum ball studs with hardened steel. You can also make small changes to bump steer with washers under the outer pivot balls on the steering link.
John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-bump-steer-002-resized.jpg  
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Old 05-24-2008, 08:31 PM   #41
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First Track Session
Hot as hell. Dusty. 100F

I had difficult conditions. Here is a report of what went well and what I had trouble with.

Front Springs
Note that the front spring should have no upper spring bucket with progressive springs pointy side up or cylindrical springs.
When I first examined the front suspension it was fairly stiff. I don't think a brick would have compressed it. The main reason was the stiction at the lower pivot balls which I removed by polishing the pin. A second reason is the spring that was on the car a 12# red progressive and the ones I tried that were softer were a little long for the car. There was preload on the spring.

I replaced a red conical spring with fairly thick spring buckets with a blue 6# cylindrical spring and thin blue spring buckets. The preload problem was better but not eliminated. I set the axle blocks to the trailing axle setting which I like. This reduced the clearance from the bottom of the king pin to the wheel rim. I had to put more preload for this to work. The first testing showed very good turn in but very bad corner exit hooking.

Inline or Trailing Axle
I changed the trailing axle to in line axle (in line with the kingpin) by turning the axle blocks over. This gave me a little more clearance which I took advantage of by reducing preload. Preload is still not eliminated but better. I wonder if the beehive springs at windtunnel will work without that upper spring bucket. I'll get some later. Now the natural tendency of these tiny springs is to sag some with use so the problem of preload will go away by itself after a few session. Anyway with less preload the corner exit problem was reduced by allowing more droop.

Ackerman
I made a change to ackerman. When the guys came back from oval carpet nats they had the servo pushed way forward. This angles the steering link back. See the first photo. I put the car on the setup plate and used my combination square to see what was happening. I set the right hand wheel to 15 degree turn. The left hand wheel measured 16.5 degrees with the servo full back (steering links straight like instructions tell you to put them). Now with the servo forward and angled links the left wheel measured 16 degrees. I lost .5 degree of ackerman. The car was better mid to late corner. I could give it slightly more power. I think I need to reduce it some more and the graphite steering arm tuning pieces that are coming from CRC may allow it.

Center Shock
I was bedevilled here again with a spring that seemed to be too long. It had too much preload with the shock collar all the way forward. I replaced the plastic spring seat with an associated TC5 (or Losi JRXS) lower spring seat. Now the collar is back a bit and I can make adjustments. I went from a silver 9 pound to a purple 7 lb. The front and back are very similarly sprung now in bump. I lengthened the rear center shock rod end to give me more pod droop. I collected the promised light scratches on the chassis, some right at the front edge and some on the edge of the battery tray. This helps you determine an equal spring rate (and was recommended by the BMI crew). After this I raised the ride height to about 6 mm front 6.5 mm at the battery tray. 5 mm rear of the pod. This gives me a high pivot which was recommended by the guys coming back from oval nats. I covered the leading edge of the chassis and battery tray edge with the black strapping tape now.

Wedge
Wedge is added to fullsize oval cars to increase steering traction. We actually do the opposite to our oval pan cars. We have a need to keep that heavy battery off the ground. You can see the preload on that right rear spring in the photo. This is actually taking off wedge or giving us reverse wedge, or left down tweak. If you tighten that collar more you take off more wedge, you tighten the car (less oversteer).

The car had very good forward traction. Very good responsiveness. A problem with corner exit hooking remains in the dusty conditions. On a high grip track, I think it is ready to race. Suggestions from the team on setup are welcome.

Likes
That adjustable servo plate is just great. I changed to the higher speed higher strength titanium gear servo with so little trouble and got it centered just right. It also allows some easy tuning to ackerman.

The appearance of the chassis is just super with all those nice red bits.

That nerf wing worked well. I got a little yellow paint on it from the slick conditions.

The car is tough. No breakages to report.

Easy to set play on the front springs.

Easy to swap trailing or inline front axles using the same part.

The pod is very long allowing the use of huge pinion gears for some applications.

The flat head screws with a large hex socket are welcome instead of philips head screws holding on the front suspension.

The car is very light allowing many high strength mods and a big servo.

Super clearance for those brushless wire leads.


Wants
A new little tape slot so I can put a small wrap of strapping tape at right angles to the primary wrap. Maybe lined up with the end of the third cell from the back with the battery back. This was popular at the nats. Some cars allow it.

I welcome opposing views on any of this.
John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-ackerman-002-resized.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-center-shock-mod-resized.jpg  

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Old 05-24-2008, 10:14 PM   #42
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First Track Session
Hot as hell. Dusty. 100F
Easy to set front play but the springs I tried are a little long for the car. These may not be CRC original equipment. John
John these are the original front springs.

You were taking about 5 degree on the left. I think you are talking about angle of the front arms. The upper arm mounts are zero degree when I built it as I had NO instructions from CRC. The mounts come in zero, 5 and 10 degree. http://www.teamcrc.com/crc/modules.p...prodID=7718914

Did ypu get my PM?
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Old 05-24-2008, 10:16 PM   #43
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Originally Posted by John Stranahan View Post
First Track Session
Hot as hell. Dusty. 100F
Easy to set front play but the springs I tried are a little long for the car. These may not be CRC original equipment. John
John these are the original front springs.

You were talking about 5 degree on the left. I think you are talking about angle of the front arms. The upper arm mounts are zero degree when I built it as I had NO instructions from CRC. The mounts come in zero, 5 and 10 degree. http://www.teamcrc.com/crc/modules.p...prodID=7718914

Did you get my PM?
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Old 05-24-2008, 10:39 PM   #44
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Rick-Thanks for the post and info on the springs. I do actually mean for Frank to Cad up and machine a custom axle block prototype if he is willing where the axle would point up at a 5 degree angle. Just a want. I may make this myself of course that would be harder but not too hard. Here is a link to the prototype. There is a photo and discussion there. There is a discussion of roll centers on the page before. I will repeat this roll center discussion in a condensed form on this thread once I get the CRC roll center tuning parts that exist in for the car. A summary is that the kingpin angle is tied to the roll center. When we put on positive camber we wreck the good kingpin angle (top going in) and raise the roll center.

I do have those reactive caster blocks coming in 0 5 and 10 degrees. I'll discuss those later as well.

A couple more items that I was asked by private message.

Weight placement on the pod.
I found the oval car is very sensitive to weight placement on the pod. I did a couple of experiments. One is I put a 1/8 inch thick motor spacer between the motor and the right side plate. This shifts weight left on the pod. The rear tires become more efficient at cornering. This tightens the car or reduces oversteer. On my previous car the pod was only wide enough to add one spacer. I got too much rear traction though and took the spacer back off. The Battle Axe pod is huge. I can move the motor over two spacers if I want more rear traction.

I don't need spacers at this point, but already I am using less rear wing from having the offset pod. The car is still tight mid corner to corner exit if I up power a bit. I have reduced the wing one more little bit.
though. If I ever get loose I can add a motor spacer or two.

As a second experiment I put the speed control on the back of the pod. There was a huge change to oversteer from having this weight that far back. I moved the speed control back forward.

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Old 05-24-2008, 10:58 PM   #45
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Spy shot by PM

Stryker Oval Chassis (LiPo ready)
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-stryker_sm.jpg  

Last edited by John Stranahan; 05-24-2008 at 11:12 PM.
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