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Old 01-31-2010, 09:53 PM   #241
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Thanks for the posts.

Motor Mods
One of the reasons I selected this car is the chassis is a little more flexible than most dual plate cars. It peforms well in the corners. Because of this and the fact that brushless cans are longer than the old brushed cans the end of the motor tends to rub the ground in a high g corner. I let the original motor get marks and then sanded it away to match the chassis bottom which is not flat. the edges are rolled up at an angle for ground clearance. You can see in the pic the light area I sanded away on this new 3.0 LRP X12 motor. I found that by aiming the leads forward a little instead of straight up that the motor screws are out of the way. Sanding away this material thus does no harm. Use a straight edge on the chassis and sand away until the straight edge does not touch the motor. The bottom is angled to the motor so you cut away a little wedge. Make sure the motor is aligned not to cut away screw heads.

Note that a previous owner enlarged the motor hole in the chassis. This weakened it an caused a break even though impact was on the front corner. I reinforced the chassis by gluing on a little graphite plate to the side. Should be good as, well used, which is what it is.

Note also lightened rear bumper as part of an overall lightening strategy.

I am using one long strip of tape and three cross strips now to keep the battery really secure.

Sway bars again
Sway bars increase responsiveness stability and steering precision at the expense of a little cornering traction.
I have increased the size of the front and rear by one size. I had small (.050) front, medium small (.060), rear now I have medium small front, medium rear(.070). I had some new scratches Sunday even on the beveled motor. I shaved a little more motor off, but the car may improve lap times with slightly more roll stiffness.
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LOSI XXX-S, Tips and Tricks, Open Mod, etc-losi-xxx-s-motor-mod-002.jpg  
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Old 02-05-2010, 09:26 PM   #242
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Track Report, Air Temp 60F

Finally the sun showed up. I managed to put a few packs on the Losi XXX-S. First a motor test. I started off with an LRP X12 3.0. I ran 6 minutes plus 3 laps on the pack. The motor temp was 190F. The speed control did not thermal but was blinking all the lights when I got back to the bench. On the track top speed was good but not better than the 3.5. Punch out of the corner was less than the 3.5. Mid short straights showed good acceleration but not better than the 3.5. I thought there might be some advantage with the tires by not hitting them so hard out of the corners but cornering did not seem to be improved. That was a quick expensive test. The second run was with an LRP X12 3.5. I finished 6 minutes plus 3 laps with it until the battery got soft. Temp was 170 F. On track performance was just better on our layout with the 3.5

I tested slightly harder sway bars than previous. I lost a little overall traction which I missed. I was able to do the tricky left side of the layout tighter and it seemed quicker than before. Tomorrow, I will remove the medium swaybar rear, readjust the shocks to balance oversteer understeer and try to get by with medium light front and rear sway bars. Slightly less roll stiffness than today but a little more roll stiffness than in the last race. Fine tuning so to speak.

Sweep Racing Premounts

My Sweep racing premount tires came in. Thanks John. They come on yellow wheels of medium stiffness. I like the stiffness of the wheel. I inspected the glue bead carefully looking for the best premount 30's to put in the photo. It was apparent they were glued by hand. I saw evidence of a couple of stalls where the glue builds up more than normal. Practice eliminates this. This does not affect performance and cannot be seen without very close examination.

The wheels mounted easily but snugly on the Losi axles and hexes showing a good fit. The 36R tires that I will test tomorrow came unglued as they are prototype units. I scuffed the wheels as instructed and superglued the tires on. I had a couple of the stalls where the tip glues itself to the tire for a moment and stops the smooth round movement necessary for a visully perfect glue job. The insert were nice tapered rubber inserts in pink. Similar in shape to Sorex inserts. They felt like medium stiffness, although the literature with the tire says they are soft. The tire itself is identified with its temperature rating on the inside sidewall, and the tire brand on the outside sidewall. Thats a nice touch that saves you grief later on.
Road test tomorrow. Lap times maybe on Sunday.
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LOSI XXX-S, Tips and Tricks, Open Mod, etc-sweep-racing-007.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-sweep-racing-premounts-004.jpg  
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Old 02-06-2010, 02:03 PM   #243
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Sweep Racing 36R vs SJ racing 36R, 66 F air temp 84 F track temp.

I set the track to medium-high traction like I do on race day. I ran a pack to fine tune my sway bar changes. Things were in good shape after a couple of upper shock mount changes. I ran 5 laps on my control tire the SJ racing 36 R. These tires had 8-12 runs on them. I ran some good laps. I noticed how quickly I gained on a blue Nitro sedan. The car was good. I traded tires and ran the sweep racing tires (new). I was rewarded with more traction and better handling. I made progress on a blue Nitro much quicker. I ran only 6-7 laps and then decided to save the tire for racing tomorrow. The tire did not fade.
Normally a new tire is a little quicker than a well used tire. This is especially noticeable on indoor asphalt. On our outdoor track there is a new tire effect but it is much smaller than idoors with stock motors. Chances are good that I will still have more grip after 8-10 runs.
The only thing left now is to test durability. I will try to count runs on this set.
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LOSI XXX-S, Tips and Tricks, Open Mod, etc-sweep-racing-premounts-004.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-sj-racing-premount-001.jpg  
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Old 02-10-2010, 08:26 PM   #244
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Default 41T overdrive

John, I've take a look at JRXS spool pulley (black) you mention on previous pages back, and its 41T. was that means your car drive ration is "overdrive" (front axle rotate faster than rear axle)?,, please advise..
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Old 02-10-2010, 09:04 PM   #245
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Faiz-I made sure my front and rear pulley matched. I don't care to overdrive or underdrive this powerful car. Both 41 and 42 tooth spool pulleys are available.
41 tooth
https://www.ssl-stormerhobbies.com/c...ns&pn=LOSA3324
42 tooth
https://www.ssl-stormerhobbies.com/c...ns&pn=LOSA3325

My race was trumped by superbowl. The tires test will have to wait.
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Old 02-10-2010, 09:43 PM   #246
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John, Thanks for the confirmation,,
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Old 02-20-2010, 05:32 PM   #247
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Sweep Racing Premounts, 70 F

I gave the tires a good test. We had some track prep to give us medium traction. The computer was on announcing times. We had a sunny day. I started with Sweep EXP 36 premounts. I am told the sidewall is a little shorter than the previous version. Indeed my ride height needed a small adjustment up. The tires felt great on the track. I was in the mid to high nineteens for the first time in practice. Previous best in practice was a low 20. I ran a set of SJR premounts which are Sorex tires on Jayco wheels. I was at my low 20 level but no 19,s. I tried a set of Sorex 40 premounts on Jayco wheels and was in the low 20's again. I had some trouble with one bead, but I had glued these tires on so that is my problem. Give a set a try. They are at an outstanding price right now.

Tekin RX8
It is starting to warm up now. I used a 90% setting on the amp limiter to keep things cool. The car was unnaffected it seems and ran a little cooler motor temp. I tried 85% on the last run and thought I might have lost a tenth or two. I went back to 90$. I replaced both fans one on the motor was missing blades. The one on the speed control I replaced with a very effective LRP cooling fan that comes with their TC model speed control.

LRP SPX8
This speed control is out now in limited numbers. I have one on order but it did not ship yet. Maybe next week. It is a 1/10 size speed control but has stronger components to handle high amperage or 1/8th scale use. It looks like it comes in the old LRP TC edition Case. I'll know for sure when it arrives. It should be lighter and more compact than the Tekin.
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Old 02-22-2010, 10:05 PM   #248
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LRP SPX8 Arrives

Here are some preliminary impressions. Firstly the SPX8 case is identical to the older LRP TC edition (Pre SXX). That is the last 1/10 scale speed control that used to work for me in mod TC on our track. A couple of racers still run it successfully at our track. See the first photo. The fan has been changed to a thicker unit. Hopefully it is as powerfully as the old fan. The weight of the SPX8 is identical to the old LRP TC edition in the photo once the wire lengths are equalized. 3.5 ounces out of the box. In the installation into the TC the wires can be trimmed shorter and you end up at 2.7 ounces. Importantly, the Rated Current: 764A/Phase is up about 260 amps from previous speed controls that I have seen this spec listed.

There is a familiar capacitor installed with nice leads internally. There is also what looks suspiciously like a Shottky diode installed externally connecting the plus and minus lead. The fan is wired internally rather than plugged in as in the Old TC edition case (not the SXX)

The LRP SPX8 compares to the Tekin RX8 at 4.2 ounces installed with capacitor.

Setup was familiar and easy. You do have to solder the BEC wire to your positive lead to run 2S LiPo. I did this under the board. I also soldered motor fan leads under the board.

The car is at our tracks weight limit of 50.3 ounces now. I lost 1.5 ounces of extra weight. Side to side weight is good. I centered the speed control in the large space for the best cooling. Thats a 3% weight reduction. I am going to notice that.

Now my demands of the speed control are simple. I don't want it to show normal temps on motor and speed control and then catch fire one day for no reason. We will have to see on this.

I turned off LiPo setting using the mode button. I do this to prevent unecessary low voltage (due to high amp draw) shutoffs near the end of the race. I turned drag brake to level 3.

I had a Black Diamond Speed control in my hand a couple of weeks ago. It may have worked in this application as it is advertized down to 3.0 turns. I could not bear the price though.
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LOSI XXX-S, Tips and Tricks, Open Mod, etc-lrp-spx8-002.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-lrp-spx8-004.jpg  
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Old 02-23-2010, 09:05 AM   #249
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John I know you like your power, have you looked at any of the GM delta wind motors? I know the delta wind is meant to have a higher amp draw than the wye winds we normally use. I know someone that has a 6T delta and he said it is easily quicker than a 3.5t..

Food for thought, also Speed Passion are bringing out slotless Cirtix motors with an 8000kv which will be a 3.5t/4.5t equivalent incase you didnt know.
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Old 02-23-2010, 10:02 AM   #250
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Conrad-I am actually quite happy with the LRP X12 3.5. I am right on the edge of the envelope power wise. Any more power and leads will desolder, batteries will dump, the motor will overheat. I tried the LRP X12 3.0 and ran the same or slower with more heat evolved by the motor. It would not work in the summer here.

by slotless, you might also mean no steel stack or core. I tested slotless motors from Mamba. That steel core in the LRP and Novak motors raises induction by a huge factor of 10 and makes the motors more efficient. I found the Mamba just ran hot without sufficient power.

I will take a look at the models you mentioned. Here are some links. Note power at 7.2 V is missing
http://demonpowerproducts.co.uk/prod...oducts_id=3949

Here is link to the slotless speed passion motors. I cannot tell if it is coreless or not.
http://www.redrc.net/2010/01/speed-p...red-bl-motors/

In the XXXS I would have trouble with this motor dragging the ground. The ring on the back end is bigger than the can and the motor appears to be longer than X12. You can already see in the above pic the metal I have removed for clearance.
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Old 02-23-2010, 03:54 PM   #251
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John, check out Shawns posts on this and the next page in that thread for insight in to the cirtix motors.

Yes I did notice the lack of a rating at 7.2v for the delta GM as well and did think it was mainly for 5 cell mod like we ran in the UK but my mate who does have one would of definately of run it on 2S lipo, he is a real power freak. I havent seen the speed in the flesh as I stopped racing outdoors years ago but I am toying with the idea for this year again, just for a bit of silly modified speed fun
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Old 02-23-2010, 04:43 PM   #252
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Conrad -Thanks for the link. Very imfomative. You might understand my skepticism here, when I was told all these same wonderful things about the Mamba. Then I put it in the wide pan car after running with Novaks 820 Watt output (measured by me) HV 3.5 and it was just average. Without sensors the Mamba had all these little drivability problems as well. Kudos to Citrix for including sensors. Now I need a picture of the insides like the one of the Mamba below. Not much room for a core in the Mamba.

The way I understand the Citrix now is that it does have a core. The core just does not have teeth extending inward. Like a Mamba, inside, wrapped with a metal core on the outside.

One thing that is puzzling is the claim that bigger wire will make the motor run cooler. When my trigger finger is on full throttle on the straight just the opposite will occur. I already pull 200 amps there based on dyno runs. Maybe the part throttle sections of the track will compensate.

May be worth a test.
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Old 02-24-2010, 07:50 AM   #253
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Surely just simple ohms law would account for running cooler? Bigger wire means less resistance so less energy will be lost as heat in the windings.
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Old 02-24-2010, 09:56 AM   #254
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resistance heating = current^2 x Resistance

Heat will go down with resistance decrease, but Heat will go up as the square of current. All my experience with mod motors indicates a fatter wire motor will draw more current during acceleration and will be more powerful but will run hotter. I'll see if I can test this motor in the future. Funds are tied up with speed controls at present.
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Old 02-27-2010, 04:24 PM   #255
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LRP SPX8 (66F air temp)
The speed control worked as planned. Lightening the car 3% reduced Practice laptimes about .3 s or about 1.5%. This is on SJR Sorex 36Rs which I had baselined previously at low 20's. Now I had one 19.6 and several 19.8s. This was not immediate however, it took a little tinkering. In the first run I felt I had too much punch. I was slipping the tires and the car would noticeably not accelerate as much and then catch and rocket forward. On the second pack I rolled on throttle slower and got into my low 20's. I ran 6 minutes plus a lap on my worst pack. Temps were 192 F motor and 127 F speed control. That is a little hot on the motor for this cool weather and a good indication the LRP is up to the task. On the third pack I went from #2 linear throttle to #1 smooth throttle. Lap times improved to the mid to high 19's. The car ran over 6 minutes. I was extremely pleased. Motor temp was 182F, also OK.

I had a sweep tire that had partially thrown a bead earlier. This was the 5th run. Unfortunately when it threw the 1 inch of bead the first time, a small tear developed in the tire. I had superglued the tear and reglued the bead and have done so previosly on other brands of tires. Today the tire threw another inch of bead and then shredded completely. Since I glued these tires, it may in fact be my fault, so I wont make a big deal out of this. I have a new set on order to race when they become available as premounts.

The XXXS just keeps getting better.
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