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Post by rocketrod on Feb 14, 2009 15:36:02 GMT -6
I recieved my 32' Freedom aluminum track and Microwizard timer earlier in the week and got everything setup so my son and I could fine tune his car for districts. :  The car would normally run 2.546 - 2.56, with an occasional 2.6x, but had a severe wiggle due to an overly aggressive CG. We moved the CG to 3/4", and replaced the lead weight with tungsten plates attached to the bottom of the car and the times dropped to a best of 2.520, but the times for subsequent runs are all over the place (as high as 2.66). We can not seem to figure out how to get consistent times out of the car.... We then decided to test a second car we built for districts to see if we would have better luck. This car was very similar, same CG and weight as the first car, but it has canted axles. Initially this car was very fast, 2.52x range, and consistent, but after about 20 runs the times jumped to the 2.55 and higher range. I re-applied graphite to no avail...in fact the car seems to be getting slower    .... Both cars are rail riders and the dominant steer the car into the rail about 1"-2" in about 4'. Any suggestions would be appreciated? |
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Post by roosclan on Feb 14, 2009 17:23:02 GMT -6
since your times are slowing down no matter how much you re-lube them, I would say check the axles to make sure they haven't migrated any. If you shifted the COM but didn't realign, that could be your issue.
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psycaz
Addicted to Speed
Posts: 86
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Post by psycaz on Feb 14, 2009 19:23:36 GMT -6
Couple of things to look at from reading the forums.
You may be seeing vibrations from the start gate which could be slowing the car down.
THe other things is maybe you are getting a lube buildup in the hubs. I would try taking one of the cars and cleaning out the wheels and see if that helps.
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Post by rocketrod on Feb 14, 2009 22:13:57 GMT -6
You may be seeing vibrations from the start gate which could be slowing the car down. I did notice the when I released the starting gate the starting pins would nudge the front end of the car to the right. To compensate for this I make sure the lever holding the starting in the up position just catches the edge of the gate. Not the best design and I can see reworking this in the near future. THe other things is maybe you are getting a lube buildup in the hubs. I would try taking one of the cars and cleaning out the wheels and see if that helps. I will keep this is mind if things don't change soon. |
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Post by rocketrod on Feb 14, 2009 22:14:50 GMT -6
since your times are slowing down no matter how much you re-lube them, I would say check the axles to make sure they haven't migrated any. If you shifted the COM but didn't realign, that could be your issue. Good point. I did recheck the alignment and it was good. |
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Post by jkracing on Feb 15, 2009 11:31:36 GMT -6
rocket, you meationed a wiggle in the car#1. did you get rid of all the wiggle. if not i would try more steer that should help the consistent times mabe even faster. i would also agree on the starting gate can make a huge diffance in times.
my 2 cents worth
jkracing
kelly
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Sappington R
Head in the Pine
"The Sappster" 10oz
Posts: 210
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Post by Sappington R on Feb 15, 2009 12:35:29 GMT -6
Rocket, I Have the exact same set-up in my garage. After table top tuning (making sure that the rear wheels to not migrate to the body in either forward or revers), I take it to the track and place the car at the bottom of the slope, let it go and watch it in slo-mo. Watch all the way, follow it down the track, get on all fours if necessary to inspect your rear wheels. Be absolutely positive that the rears are not touching the center strip. In order to accomplish this you may need to take a little of the front dominant side- most league racers agree that about 1/16" is ideal. If you want examples, I suggest looking a builders cars on the PWDR board. Guys like "Proquest" are very good at this.
One other thing about the wiggles- it could be that your axle holes aren't quite right- may wan to re-check by just putting drill blanks in each hole and inspect carefully from every angle by eye. It will be very revealing.
Hope I've helped.
Sapp.
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Post by rocketrod on Feb 15, 2009 13:07:28 GMT -6
rocket, you meationed a wiggle in the car#1. did you get rid of all the wiggle. if not i would try more steer that should help the consistent times mabe even faster. i would also agree on the starting gate can make a huge diffance in times. my 2 cents worth jkracing kelly The wiggle disappeared when I moved the CG up to 3/4", the CG was previously at 1/2" Rocket, I Have the exact same set-up in my garage. After table top tuning (making sure that the rear wheels to not migrate to the body in either forward or revers), I take it to the track and place the car at the bottom of the slope, let it go and watch it in slo-mo. Watch all the way, follow it down the track, get on all fours if necessary to inspect your rear wheels. Be absolutely positive that the rears are not touching the center strip. In order to accomplish this you may need to take a little of the front dominant side- most league racers agree that about 1/16" is ideal. If you want examples, I suggest looking a builders cars on the PWDR board. Guys like "Proquest" are very good at this. One other thing about the wiggles- it could be that your axle holes aren't quite right- may wan to re-check by just putting drill blanks in each hole and inspect carefully from every angle by eye. It will be very revealing. Hope I've helped. Sapp. I will re-check the alignment again as like everyone has mentioned this may very well be the culprit. I am also going to recheck the track to ensure it is level and the transition between each section is smooth. Thanks again for all the suggestions. I 'll post my results later. |
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Post by thebeav on Feb 15, 2009 23:43:11 GMT -6
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Post by rocketrod on Feb 16, 2009 19:50:04 GMT -6
The saga continues  (sorry for the long post)... I had the den leader bring a car over to benchmark the track. His son's car ran consistent 2.50xs with a couple 2.53s & a 2.54. Alignment of the cars drastically changed the times as is to be expected. So we are thinking the inconsistent times are related to my son's cars and not the track. I have noticed my the nose of my son's cars, all of them, tend to adhere to the starting pin. The nose of each car is 1/4" thick. We rechecked the track alignment and cleaned the track with no improvements. At this point we reapplied graphite to the wheels and ran the cars again adjusting CG/COM... - Car #1 - Moved weight around on car adjusted CG and COM with no improvements in consistency. The alignment was not affected when moving CG/COM.
- Car #2 - Replaced canted axles with straight set and car is faster that car #1, but times are also inconsistent.
- Car #3 - Had enough parts already to assemble one more car. Car was by far the fastest with a 2.509, but like the others is inconsistent.
Typically the cars times varied by as much a 0.03x from run to run regardless of who staged/started the race. I am at a loss at to what to try next. The only noticeable difference that I can see is that cars #1 & #2 have quite a bit of graphite on the tread surface and seems a little sticky. What is the best way to clean the tread surfaces with the wheel installed? |
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psycaz
Addicted to Speed
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Post by psycaz on Feb 16, 2009 20:09:37 GMT -6
Well, with the cars sticking to the pin, you could rub graphite onto the nose to slick them up. I would see what others have to say about that.
Have you tried running the cars with the wheels against the rail to start and see if the times tighten up?
You say the other car that was brought was running consistent, but also turning some times that were about the same over than what you are expecting - that 0.03.
Did you see a pattern as to what caused that to happen?
I am wondering if it is just something with alignment or bounce with the start gate.
Since you still saw that same type of increase - that .03 - that is making me think you might be getting some bounce from the gate.
The track we practice on does the same thing, very inconsistent runs. I ended up not using the pin to pull the release, but already having it pulled while holding up the pins then releasing them by hand. Easier to show than explain here - but it did tighten up my times a TON.
I was getting bounce just by the way the slide pull ( think an sliding latch that would lock a door) would let the gate slam back hard. Drove me nuts for a long time. Times got lower too as the track didn't bounce at the top and that will affect times.
Hope you are able to find it, or get it to a level you can live with.
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Post by rocketrod on Feb 16, 2009 22:53:29 GMT -6
Well I finally made some headway, or at least it seems like it. I started looking at the incline section of the track and notice all four legs of the stand were not sitting flush on the ground. I shimmed the legs and and made sure everything was level. I also added set some weight on the back legs and the track seems very solid now. In addition, the area were the track transition from the incline to the flat section would flex. I took a some 1x2 and slid in under the track until supported that area and ran the cars again....
I ran cars #2 & #3 a total of eight times, four in each lane. Four runs were solo and four runs head to head alternating lanes. Both cars were slightly faster running solo, but they were both very consistent!
Car #2 fastest time was 2.519 (tied a personal best), the slowest 2.536 and an average time of 2.5273.
Car #3 fastest time was 2.53 (2x), the slowest 2.542 and an average time of 2.5346.
Overall I am pretty happy. Both cars are much faster than the car we raced in a our pack races on our new track. I know from experience these results will vary from track to track. I will test again tomorrow and if the results are consistent I will start trying to modify the slower car to make it faster.
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khouse
Head in the Pine
Posts: 199
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Post by khouse on Feb 21, 2009 19:17:01 GMT -6
I have found that the more you move your COM back the more you have to steer your car into the rail. The lighter the front end the less traction you'll have between the wheel and track. You have to adjust accordingly.
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Post by rocketrod on Feb 22, 2009 21:40:39 GMT -6
I have found that the more you move your COM back the more you have to steer your car into the rail. The lighter the front end the less traction you'll have between the wheel and track. You have to adjust accordingly. Good point. I was wondering how people put so much weight in the rear and the car not wiggle real bad. Any suggestions on how to aggressively steer the dominant wheel into the rail? I have the Pro-Rail Rider tool, but I am not really impressed with its ability to cant the axle. |
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khouse
Head in the Pine
Posts: 199
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Post by khouse on Feb 22, 2009 22:07:05 GMT -6
That's a crap shoot. I'm building a car right now with 7/16 COM. I'll bet I'll have to steer it 4 inches in 4 feet to start out. I don't have a test track so I really won't know until it races. When your car is at speed everything changes. I wish I had a track at home!
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Post by railrider on Mar 16, 2009 1:03:50 GMT -6
I am a little late with this thread and this is my first post. It has taken me many thousands of runs on my own wood 39' track to come to the conclusion that you may have to set more drift when rail riding than you might expect. I am using a Newbold timer (2 lanes) and have also seen some inconsistent times and rear end wiggle, even with what I consider near perfect alignment - that is, the rear wheels staying outboard against the axel heads, the raised wheel totally free of the rail and car body. Also rear wheels remaining outboard with the car running forward and backward. I have tried the suggestions on this board of drift of just a few inches but I always have to resort to increasing the drift on my tuning table (6 feet long) to sometimes 9 or 10 inches! This is counterintuitive since the frictional force of the dominant wheel against the rail would be increased, but my timer verifies the reduced run times. I usually run the cars for 10 runs, and I can see this visually by much smoother and straight runs with no wiggles. I don't always achieve the "wiggle free" results but the increased drift does seem to help. I think my times would be improved if I could really only be able to run with less drift but I haven't figured out how to achieve this yet! Anyway you might try more drift and let us all know the results.
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beakerboysracing
Head in the Pine
You can pick your friends, you can pick your nose, but you can't flick your friends across the room.
Posts: 167
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Post by beakerboysracing on Mar 16, 2009 15:45:22 GMT -6
I am a little late with this thread and this is my first post. It has taken me many thousands of runs on my own wood 39' track to come to the conclusion that you may have to set more drift when rail riding than you might expect. I am using a Newbold timer (2 lanes) and have also seen some inconsistent times and rear end wiggle, even with what I consider near perfect alignment - that is, the rear wheels staying outboard against the axel heads, the raised wheel totally free of the rail and car body. Also rear wheels remaining outboard with the car running forward and backward. I have tried the suggestions on this board of drift of just a few inches but I always have to resort to increasing the drift on my tuning table (6 feet long) to sometimes 9 or 10 inches! This is counterintuitive since the frictional force of the dominant wheel against the rail would be increased, but my timer verifies the reduced run times. I usually run the cars for 10 runs, and I can see this visually by much smoother and straight runs with no wiggles. I don't always achieve the "wiggle free" results but the increased drift does seem to help. I think my times would be improved if I could really only be able to run with less drift but I haven't figured out how to achieve this yet! Anyway you might try more drift and let us all know the results. The thing you have to remember when rail riding and using a bent axle up front to steer the car is that if you angle is correct on the bend( I use 3 to 4 degrees) and the bend is down, the wheel will actually be rolling down the center rail instead of rubbing. This helps offset the friction generated by large amounts of steer because you are rolling on two surfaces instead of rubbing on one. Outside edge of the wheel rolling on the track, inside edge rolling on the rail. Each car is different, and a track is crucial to find the sweet spot. Scott Beakerboys |
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Post by railrider on Mar 17, 2009 0:27:09 GMT -6
Scott,
When I visualize what you are saying about the way the dominant front wheel runs with the axel bent down it makes sense. I have never seen that geometry discussed on this board. Canting the wheels has been described as bending up for both rear and front axels, but I can see the rolling versus rubbing advantage for the down bend for the front - I will try it!
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Post by shadetreeracing on Mar 17, 2009 12:16:23 GMT -6
beak hit the nail on the head try it you'll see a big difference some don't like sharing secrets like others do  |
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