LOSI LST XXL Conversion ideas

[mistercrash]

This is what I had.

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1.8333333333333333
Other Ratio: 1
Spur Tooth Count: 54
Pinion Tooth Count: 24
Total Voltage: 22.2
Motor KV: 1577
Tire Diameter (inches): 5.65
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0.008
Spur/Pinion Ratio: 2.25 : 1
Total Ratio: 13.64423 : 1
Tire Circumference (inches): 17.75 inches (450.85 mm)
Rollout: 1.30:1
Total Motor Speed: 35009.4 RPM
Vehicle Speed: 43.13 mph (69.28 km/h)
Effective KV Value: 1577
KT constant: 0.86 oz-in/A

Now I opened the tranny and took the CD out and put back the stock Traxxas spool. I checked the gears and all bearings and everything is in top shape in there. My wheels are well balanced. I always balance my wheels the best I can. There's no binding anywhere on the drive train, everything spins very freely. The body had holes in the front grill and a big round hole in the windshield. Plenty of air flow there. I was running a pair of Zippy-H 3S 5000 mah 20C. The truck weighs very close to 14 pounds with 3S lipos in it.

While I was working on the truck, I reinstalled the stock XXL Losi wheels and tires so I changed my gearing. Now when I use Brian's top speed estimator, I never factor in tire ballooning. Maybe I should so I recalculated with .25'' tire ballooning this time and this is what I'll be trying.

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1.8333333333333333
Other Ratio: 1
Spur Tooth Count: 58
Pinion Tooth Count: 19
Total Voltage: 22.2
Motor KV: 1577
Tire Diameter (inches): 6.75
Tire Ballooning (inches): .25
Motor Current Draw: 0
Motor Coil Resistance: 0.008
Spur/Pinion Ratio: 3.05 : 1
Total Ratio: 18.51147 : 1
Tire Circumference (inches): 22.78 inches (578.52 mm)
Rollout: 1.23:1
Total Motor Speed: 35009.4 RPM
Vehicle Speed: 40.79 mph (65.52 km/h)
Effective KV Value: 1577
KT constant: 0.86 oz-in/A

[nuz69]

Ok
The batteries are too weak :(
Here in France we experienced very bad things with 100A discharge (5000, 20C) zippy lipo, even on light buggy, so in heavy Monster truck like yours ... Zippy batteries are often overestimated in their discharge capability, that's why you have this kind of temp in yours. The batteries will start to take volume in the time :( A good temp for batteries is 120 MAX !
Keep us posted if the setup without CD heat less !

[mistercrash]

Today is another extremely hot day in this heat wave we're having up here in the Great Toronto Area. So I took out the LST again in the same spot and let it rip on 6S. I over did it again as I blew the front diff after 5 minutes but I kept on going despite the loud clicking sound and at the 22 minute mark, I broke a front shock shaft. Good news is, the temps were great even though it is 40 degrees outside with the humidex.

Motor: 162
ESC: 134
Lipos: 109
Tranny case: 106
Front diff: 162
Rear diff: 141

So lesson learned here, when using the Top Speed Estimator, it is important to factor in the tire ballooning because since I didn't do it before, I was geared to low every time.

[mistercrash]

My truck is resting right now until I get the new TiNi shock shafts and a couple more parts in the mail to fix it. On the shock with the snapped shock shaft, I also noticed that the shock cartridge had started to come out of the shock body. So I searched on the LST forums for a fix and I came up with the idea of straps to limit suspension droop. I used zip ties that are secured to the upper arms and sandwiched between the shock towers and the CF plates I made to reinforce them. I'll be trying those out when the truck is fixed.

Compressed


Resting


When the suspension is extended, the straps let the arms drop almost fully, just shy of full extension to releave the stress on the shocks.

[mistercrash]

So I have a snapped shock shaft and a bent one. While I'm waiting for the new shafts to arrive and start playing with my truck again, I searched the web to find stronger shock shafts. I couldn't find any. I'm thinking that 5 mm shock shafts would be stronger then the original 4 mm shock shafts. Problems would be, where to find them and how to make them work in the shock cartridges.

Is there any manufacturer that makes 5 mm shock shafts and cartridges? If you know of any, please tell me.

In the meantime, I started looking at the stuff I have in the garage to try to make my own. My E-Revo's pushrods are 5 mm in diameter and are about the right length. Just a little too long. They have M4 threads on each end.



So I grinded one end to make it short enough to match the LST shock shaft. The center hole of the shock piston would have to be drilled to 4 mm and a 4 mm washer with a 4 mm lock nut would be used to secure the piston to the shaft. Then to shorten the opposite end to match the length and put some M5 X 8 threads on the shaft.



With the shock piston drilled to 4 mm and the shock ball end drilled to 4.2 mm, this is what it looks like assembled, with the stock assembly next to it for comparison.



The shock cartridge has to be disassembled to enlarge the center holes of the cartridge and the snap cap to 4 mm. The spacer between the two O rings inside the cartridge either has to be drilled or a new spacer has to be found or fabricated. I had a spacer with a 4 mm hole in the middle but it didn't have the right length so I cut it to match the length of the stock one as close as possible.



I was able to squeeze the new 5 mm shaft in the cartridge using the stock O rings but it is too tight so a new set of O rings with a 5 mm ID and 2 mm cross section (9 mm OD) would be needed. I could get durable Viton O rings for cheap from this guy on ebay.

http://cgi.ebay.com/10-x-Viton-o-rin...item4145e04d6e

So what do you think? I made one shaft to see if it could be done without to much trouble. Would this be something that would benefit the LST?