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Old 04-19-2007, 08:34 PM   #1141
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*cough* what? flexures? lol where's marty when we need an update to the f1 car. when i finally get settled in after all the stuff going on here with work n such, i'd go broke just getting all these neato cars to tinker with.
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Old 04-19-2007, 08:44 PM   #1142
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Well not exactly flexures, but this lower arm has quite a bit of fore and aft flex due to its barrel shape. Should prevent breakage. The upper arm is quite rigid, so I have built in some extra fore and aft flex by supporting it by a cantilevered aluminum beam that attaches only at the front and by giving its plastic support a narrow bolt spacing. This is a durability thing rather than a performace thing. Steering grip was phenomenal at the last race. I had some troubles with water on the track. I make no apologies for the eventual price. The performance is truly outstanding.

Have not heard from Marty. He is responding to some e-mail. His health has taken a turn for the worse I suspect.

John
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Old 04-20-2007, 05:20 AM   #1143
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john, it's the modern age. it's all done virtually with cameras asn lcd screens...
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Old 04-20-2007, 05:50 AM   #1144
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Is this powell conversion to make a 235mm car, and if so, where is it available and how much?
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Old 04-20-2007, 07:23 AM   #1145
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Quote:
Originally Posted by JoelV
Is this powell conversion to make a 235mm car, and if so, where is it available and how much?
Joel,
E-mail or PM me for more info about the MAX10 chassis.

Doug
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Old 04-20-2007, 07:01 PM   #1146
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Traction Poor from dust at first. Airtemp 85F track temp 110F.


I got my new maxamps.com batteries in. Took them out for a test. Quite a bit faster on the straight. I had 3 minutes longer runtime. Quite a bit higher motor temp from the new batts, longer run time possible, and increased air and track temperatures. After the first run the 3.5R was at 176 F. I opened up the topside vent on the body a bit which is a bit small on this Associated Nissan Body. Usually after I run two complete packs the car starts really ripping around the track as it has picked up most of the dust from the race line. This was true again. The new front end was working superbly. I gave the car a bit more antisquat, now it felt just like the older 3-link chassis. I was lacking just a bit on forward traction before the antisquat change. Then the GTB let out the smoke and took one of the new batteries with it from an internal short in the speed control. When you send one back like this the tech guy tells you you must have had an external short. Well external shorts leave a heavy evidence trail like a motor on fire. No such trail here just an almost melted controller. The controller is well used at this point and may have been causing the excessive amp draw and lowered run time I was experiencing from a deteriorating condition. I have a MambaMax on the way, but sadly have nothing to run this weekend. The Tekin is still on back order. The Trinity N60 motor is on the way.


John

Last edited by John Stranahan; 04-21-2007 at 12:58 PM.
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Old 04-20-2007, 07:11 PM   #1147
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send it in anyway..
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Old 04-21-2007, 12:47 PM   #1148
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Breakage Report Front Suspension
I had a severe crash at the end of the straight. I was running up to the back of a Nitro 4-w-d car and was waiting for him to commit to the sweeper so I could make a pass early. Instead he hit the brakes hard. I hit the car with the right front. My car flew about 10 feet and landed on the tires. It was my fault, I offered apologies. Now the suspension was still in good working order. No breakage. Inspection at home revealed a lower inner hinge pin had bent. This indicates to me that The more flexible Delrin might be a better material for the suspension mounts. The arms held up well.


Complete Metdowns
TallyRC-sad to say this GTB controller has been to service 5 times. 5 times in the touring car, The last time there was a serious fire with 20 foot smoke plume and flames when I turned the car over. Gator aid put the fire out. The message on the repair order was "Typically melt downs like this have some "help" in the car, a battery short, a wire short something to make the fire."

Welll there was no "help" that time: there was some "help" this time. The front motor bearing was seized up solid. The bearing cage was completely shredded on inspection. There was plenty of grease still left. It is possible that a ceramic bearing is not suitable here. The ball may crack from vibration. I have replaced it with the $1:00 Avid steel bearing with steel ball bearings. These appear to be lubed with some type of grease.
"The second message was warantee replacement as a one time courtesy." My only excuse to send these products back is they are supposed to have a Thermal shutdown feature to prevent the controller from "meltdown". I have not run without the blue wire on the motor either. I have tried strange methods too cool the motor though. Some of these repair orders contained the message "failure of the thermal protection circuit"

Novak has been more than helpful and their controller lasted quite a while in the pan car. These things really need better cooling like maybe a liquid inside the case. The sphere comp is in the same condition "melt down" so the problem is not unique to Novak.

I have to admit that I act like a tester to find the limits of performance of these products.

John

Last edited by John Stranahan; 04-21-2007 at 03:34 PM.
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Old 04-21-2007, 04:41 PM   #1149
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John,

I wonder if the Novak guys monitor this thread. It would be interesting for them to hear about some of the repeated problems you're having, pushing their gear to its limits.

Have you found any correlation between the front bearing's ABEC rating, and its life?
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Old 04-21-2007, 04:46 PM   #1150
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yea a seized bearing is a problem.. i wonder if a small "foam thing" from offroad ball cups, infront of the bearing would help keep it clean?


one funny thing (to me atleast) on my gtb is the orientation of my cooling fins.. tho "open" ends of the fins is right into the plugs on one end, and the wires on the other.. certainly not the optimum alignment for airflow from the fan.. anybody know if these can safely be removed and rotated 90 degrees?
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Old 04-21-2007, 07:07 PM   #1151
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I experimented giving the heatsink more airflow by putting The GTB on the side in the touring car. Then I could run the heavy lead wires from the bottom. I removed the plastic from the plugs on the other end. Did not help much. I don't think you can rotate that heatsink.

Failed Bearing
The 3.5R bearing came with seven balls and had seven after failure. None were cracked or broken. I cleaned the race and inspected it. They look pretty good. No brinneling from crash damage (little dents in the races). The balls looked good under magnification. Only problem was the cage was broken up and ground to pieces. I usually don't find grease in a bearing in this broken up condition. It had gobs of grease left. I don't know what is causing this damage. Rotor was new. Clearance of the shaft on the inner race of the bearing seems about normal. .0008 inch. Finish on the outer race was somewhat dull or poor. This might be caused by dirt entry. I was thinking of a seal, It might be worth the extra friction. What I would like is a teflon sealed bearing. I'll look for a supplier. That was one expensive failure. The speed on the straight was normal. Speed out of the corner was normal and then the car just stopped on corner entry. Started heavy smoke when I was on the stairs. The bearing felt good before the session when I rotated the motor by hand with the spur.

Where is that stalled rotor shutdown or thermal shutdown when you need it.

Note my 4.5 did not have excess trouble with this bearing. It might have something to do with vibration from the gears. They don't mesh particularly well at this ratio. Gears are short lived.
John

Last edited by John Stranahan; 04-22-2007 at 08:31 AM.
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Old 04-21-2007, 07:38 PM   #1152
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I have had LRP Sphere comp and GTb's suddely heat up and catch on fire, too. This happenend several times, especially during the hot florida summer weather. Switched to the Castle Creations Mamba Max ESC w/ 7700KV Cm36 BL motor from Castle Creations, and it the Mamba Max system is just more rugged and tough. Its as fast as 3.5 systems, but you can gear it 2-3 teeth higher on the pinion for greater top speed if needed and the temps are really good. When I run at the large 160FT straight of the 1/8th scale track, I have geared it 5 teeth higher than the max for the GTB and the temps are 184-188F after 6 minute runs, with just a heat sink! I just got sick of running into thermal pblms with the GTB and going thru the hastle of replacing them and missing weekends of racing due to the tech repairs.
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Old 04-21-2007, 07:54 PM   #1153
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I don't imagine that Novak monitors this thread. Now here is a thought. The bearing is spinning at 63,000 rpm at the end of our straight geared 90/12 at aproximately 60 mph. I wonder if that cage is just failing from centrifugal force; the bearing is not rated for a high enough RPM. These forces would be larger in the oversize Novak bearing and not a problem on the lower powered motors. I have not determined the difference between expensive and cheap bearings yet. Seem to be about the same. The ABEC rating is not reported. I have not used the $1.00 bearing yet.


The mamba max is on the way.
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Old 04-22-2007, 03:02 AM   #1154
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I had the races break on the ceramic bearings I used on my rear axle.
I suspect the problem with a ceramic bearing is like using a stainless steel screw in a high stress area. They have no "give", they simply break.

The revs these 3.5's run are simply insane.
I think the future is more to sensorless motors which run way less revs, but reach the same speeds with taller gear ratios like the GM and Hacker series.
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Old 04-22-2007, 08:34 AM   #1155
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was that with a ceramic hybrid or all ceramic? i imagine a hybrid would be better, with ceramic balls and stainless all else.. the ceramics have better dimensional stability under temperature so i imagine you could probably use an abec 5 or maybe 7.. call boca and ask them.. bocabearings.com. i'll ask my dad if i get the chance today, he used to work for fafnir as a matallurgical engineer.
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