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nbTMM

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Everything posted by nbTMM

  1. If you only ever intend to run them stock, then there is not much difference. Some notable advantages of the TT-02 however: - The differential cover is split horizontally instead of vertically, so grease/fluid leaking from the differential gear over time is captured, instead of leaking onto the ground. - The chassis supports square profile 2S lipo batteries without modification. TT01 requires the ribs to be cut/dremelled to fit packs other than a typical round cell 7.2v NiMH. - Way better aftermarket support. Aftermarket TT01 parts dried up quickly after the TT02 was released.
  2. Good thinking with the steering rock guard - I might steal that idea
  3. They are HXT connectors - prevents plugging in batteries / ESCs backwards accidentally. For inline connections there is zero chance of them exposing metal and shorting together unlike heat shrunk bullet connectors. Not pretty, but functional.
  4. Moving the link attachment point closer to the bar pivot makes the bar effectively stiffer as the arm has less leverage to twist it. Although ugly, it can be done should a thicker bar not be available, and the link angles aren't pushed too far such that they bind.
  5. Probably all the hopups trying to turn a TT02 into a plastic tyre drift car. It never handled how I wanted it to and just wasn't enjoyable to drive, probably because I didn't have the correct surface to run it on. It's much more enjoyable as an overpowered rubber tyre go-anywhere basher.
  6. From hobbyking: https://hobbyking.com/en_us/turnigy-receiver-pack-2300mah-4-8v-nimh-flat.html Generally with NiMH you get what you pay for however. In my transmitter I use Energizer 'recharge' AA NiMH, the made in Japan ones which are well known for being some of the best cells around. You will likely need to source them through an electronics distributor though as Energizer sell several different types of NiMH cells under similar names and appearances - the ones sold at mum and dad brick and mortar type stores are almost always crappy chinese made cells. There are also fakes being sold so avoid trying to source quality cells from places like eBay. A a low-power device like a transmitter isn't very demanding though, so likely cheap NiMHs will get you decent runtime and lifespan.
  7. I think even if you cut it and glued it back together perfectly, it would still be out of round because the tyre is going to want to maintain the radius that is was molded as. It will probably assume an egg shape not unlike your last picture.
  8. Same problem here. Also, embedded Youtube videos appear with an extremely narrow portrait aspect ratio.
  9. Drift car is no more. I ended up making it RWD, which required some yeah racing parts such as the aluminium steering and suspension arms to get adequate steering lock while maintaining reasonable steering lock. I decided though, that plastic tyre drifting wasn't really for me. It requires a really smooth surface like polished concrete, otherwise the 'tyres' get scuffed up too much and generate too much grip, and constantly wear into a conical shape on rough surfaces which means that how the car handles constantly changes as the tyres wear. Left: drift car. Right: a new TT02 project that I'll cover at a later date. The drift car was converted back to 4WD and rubber tyres because I had way more fun with it like that. My goal with this car is to make an all-weather all-terrain car that I can beat on and doesn't require much maintenance. I always avoided running my TT02s in the rain or gravel/dirt because the tub just ends up getting drowned or filled with debris and bearings rust solid. With this car, that will change! Also, I will try to use as many stock and half-worn parts that have come off my other cars. The first phase of making it weather proof was to retro fit a set of XV-01 mudguards or wheel arch liners. This was accomplished with some aluminium mounting bars which I attached by using longer bolts at the front propjoint bearing cover, and the rear upper suspension arm mount respectively. I also made some custom side trays to block water and debris being thrown up between the chassis and body shell. These are made from FRP - actually 1.6mm printed circuit boards that I had made. I goofed some of the hole locations, but managed to salvage them by drilling some new locations. They were designed to make the chassis exactly 190mm wide to suit another project, but I cut these ones down to the same profile as the Lancia Delta Integrale shell so they aren't so obvious. Some closed cell foam seals the gaps between the guards and body. Just in case water does get in, waterproof electronics were installed. The ESC is a Hobbywing WP-8BL150 which is overkill but waterproof (electronics completely potted in resin) and reasonably cheap. The motor is a Trackstar 7.5t brushless which is run as sensorless, effectively making it waterproof. Due to running sensorless, the motor endbell now has no effect but I can set the timing to 26.5degrees in the ESC which makes this motor about 4400kv. Spur gear is a 61t 0.6 mod from a TT01, which if ground down slightly fits on the TT02 shaft. Pinion is 27t. The GT5 receiver I pulled apart and gave the circuit board a generous coating of epoxy resin. For the steering i'm using the stock plastic parts, however with some aluminium bushings that I found in my parts box pressed into them. Together with M3 bolts that have a smooth shaft near the head, this reduces the slop in the steering a little bit. Not as good as aluminium ball bearing steering, but cost me nothing and is more resistant to water and dirt. The steering servo is a Goteck BL1511S brushless, which has rubber o-rings so should be water resistant even if they don't advertise it. This servo is extremely fast and quiet, but its deadband does not meet the advertised spec at 6.0V (ad: 1us, reality: >10us) so I don't recommend it. At 7.4V it is better (<3us) however I don't have any ESCs which have a high voltage BEC, and don't plan to get one anytime soon so I'll manage with the slightly sucky dead band for now. As usual I use a Tamiya #51000 servo saver and 3racing aluminium horn since they just work. Continuing the theme of using parts already on hand, I installed a 30mm motor fan using the plastic mount that comes with the TT02 kit. I opened up the restrictive grille with a dremel to aid airflow and cut away the switch mount to clear the terminals of the brushless motor. I usually use a 40mm fan with a custom mount, but thought I'd give this a try. It works well! Suspension was changed to ZD racing front buggy shocks all around. They are huge/long compared to regular on-road shocks. For the rear, i'm using a custom made FRP shock tower which has additional mounting holes to accommodate longer shocks, together with a 6mm spacer installed internally on the shock shaft to limit droop. Diffs are TB01 diffs which are cast aluminium and will take more power than the standard plastic ones. Drive shafts are metal dog bones and cups as per TT02RR - I chose these as they are more resistant to water and debris than 'CVD'/universal shafts. When they get dirty they clatter a bit, but it's better than a universal jamming up from dirt or rusting solid. Currently the rear diff is filled with 1million cst oil and the front with 100k cst oil, but I'm still playing around with weights. At the front, the droop of the shock needs to be limited more because the front suspension lower ball joint and drive shafts do not support as much travel as the rear while turning. Putting 9mm of spacers internally achieved the right amount of travel but was too stiff as making the shock overall shorter pre-loads the spring. The front springs need to be softer on a TT02 to utilise the travel of the front suspension because the chassis has a rear-biased weight distribution. I ended up using a 3mm droop spacer internally and put a 6mm spacer externally. This makes the shock too long to work with my FRP tower, so I reverted to a setup I had used to run long shocks on a TT02 before - an aluminium plate which bolts to the standard plastic shock tower. The new front shocks are too big for the standard front bumper arrangement to work, but some trimming and a bolt solves that. The guards and foam are really effective at preventing water and debris getting thrown directly by the tyres from entering the tub. They are less effective against fine dust, or if you slide the car sideways through a deep puddle. When driving on gravel, the steering can be jammed up occasionally by larger rocks. Nevertheless, the car is definitely easier to clean after use. I have all rubber sealed bearings which I packed with wheel bearing grease (for 1:1 cars). After use I remove the battery, hose it down, shake it out and leave it to air dry - no issues yet! The side trays are less pretty after being pelted with gravel though I can't say I didn't expect that.
  10. I'd go with the 15T if your esc supports it. It'll be substantially faster than the stock motor, but shouldn't push the standard TT02's drivetrain past it's capabilities. 20T will only be a little bit faster than stock, so probably not worth the upgrade.
  11. I just drill a smaller sized hole (e.g. 4mm), then the final size (e.g. 6.5mm), with regular drill bits. I then clean the burrs with a step drill bit by hand. Press a piece of wood up against the back of the polycarbonate shell when drilling to avoid tear out.
  12. Kind of expensive for what it is. Gives me ideas for rigging up two arduinos and a servo to pan my GoPro though
  13. Pull issue might be due to wheel alignment? I notice mismatched wear particularly on your rear tyres. Another thing to check is that it isn't the steering servo itself steering when you punch the throttle. Weak BECs, batteries and/or cheap servos are known to cause problems when accelerating hard due to electrical noise from the motor and/or voltage drop at the battery. This is easy to test - hold the car in the air and punch the throttle, check that the steering servo doesn't jerk to one side. Sometimes a "glitch buster" capacitor connected to the receiver can help, but hardly ever fully cures the problem in my experience. Gears should be 0.6 mod unless the previous owner has fitted a 48dp spur. If the spur is the standard 0.6 mod one, excessive noise might be caused by the mesh being adjusted too tight, or just worn out teeth. Otherwise, 24t and 35t 48dp pinions are about the same physical sizes as the 21t and 31t 0.6 mod pinions you currently have. Just about any 48dp anodised aluminium pinion will do the job, they are fairly standardised. Make sure it has a 3.175mm (1/8") hole for the motor shaft, as 48dp pinions for 5mm shafts exist as well.
  14. This final drive ratio (FDR) chart from a Hobbywing 3650 motor datasheet should be a good starting point. An FDR of 7.0:1 means that 7 rotations of the motor results in 1 rotation of the wheels. The formula to calculate FDR for a TRF201 is: FDR = (spur_teeth/pinion_teeth)*2.6 So for example a 25t pinion and the standard 79t spur gear would get you FDR = (79/25)*2.6 = 8.22, which is safe for motors down to 10.5turns in a buggy, but might have a lower than desirable top speed for motors >13.5turns. The FDR suggestions above are based on circuit racing, so if you run on smooth surfaces (on-road) at high speed you can probably afford to run a lower FDR, and if you run on slower rough terrain like grass you might need to go to a higher FDR. If in doubt, start with a higher FDR and see how hot the motor gets. If the motor is running too hot (can't hold your finger on the can for more than a few seconds), you need to go to a higher FDR - a pinion with fewer teeth, or spur with more teeth. If the motor is running cool, you can afford to go to a lower FDR (more pinion teeth or spur with fewer teeth) which will achieve a higher top speed, but slower acceleration. There may be a limit to how small or large of a pinion and/or spur gear will physically fit in the car, so if you're making a big alteration to FDR you may need to change both gears to come up with a combination that physically fits.
  15. 6A is for brushless 540 motors. Most brushless 540 motors will be set for 2-4A no load current out of the box and it only requires a handful of degrees adjustment to get them up to 6A. If you adjust the timing to achieve minimum current draw, you've adjusted the motor to 0degrees timing, which is not where the motor produces peak output power. 6A no load is a rule of thumb that generally corresponds to peak output power (give or take 5-10%) but definitely not peak efficiency. A good 21.5t motor at moderate timing produces about 120W of mechanical power at about 50-60% efficiency (80-120W as heat) at half it's max rpm, or about 80W of power at 75-80% efficiency (20-25W as heat) near three quarters of it's max rpm. At 0rpm it produces no mechanical power, uses hundreds of watts of power and has 0% efficiency. That's why a motor runs HOT when you put long gearing in the car, because it spends more time at lower rpm where it has poorer efficiency. Increasing the timing also increases the Kv of the motor, which has the same effect as longer gearing, therefore it will run hotter. As long as your no load current isn't ridiculous (like >15A), and you readjust your gearing to compensate for a change in Kv, the reduction in efficiency of the motor should be manageable. Adding no load current just adds a static amount of heat output at every rpm. If you're already chucking away an average of ~50W as heat at 0deg timing, it's not a big deal to make that ~70-80W if it gives you 20%+ extra power on track. If all you care for is reducing temps, just set to 0 deg.
  16. When you say the car jolts, do you mean that when you try to drive forwards or reverse, there is a jolt and then no further progress? Check one of the differentials isn't installed backwards - that would cause the front wheels to try to turn in the opposite direction to the rear wheels, and it won't go anywhere. If you hold it in the air when you press the throttle, wheels should turn. Otherwise, if you mean that the motor sounds like it is spinning freely (as if it's removed from the car), then either the motor spur/pinion gears aren't meshing properly (motor mounted to wrong holes on the motor mount?), one or more gears have broken teeth, or something in the drivetrain isn't assembled properly.
  17. With your radio gear, or something they had in the shop? If the latter, you have to do it again with your radio gear because your radio may have different end points than the shop's radio. My thought is that when your transmitter is at 75% trigger, the ESC considers that to be 100% throttle because of how it has been calibrated. So the ESC simply gives up when you go full trigger as it is receiving what it considers to be way more than 100% throttle, which is an invalid signal. If that is indeed the problem, re-running the ESC calibration should fix it because the ESC will map full trigger to 100% throttle as it should be. There may also be a secondary issue at play as Superluminal pointed out: if by 'working in reverse' you mean that when you move the trigger to the brake/reverse position on your transmitter the car drives forwards, you need to rectify that first by reversing the throttle channel on your transmitter. Simple transmitters usually have a switch labelled 'TH REV' or similar. Then go through the ESC calibration again.
  18. The Yokomo Crown body is 275mm wheel base isn't it? That's longer than normal. Standard touring car wheel base is ~255-260mm. If the wheel arches aren't cut from the body yet, you could cut the rear arch slightly forward and the front arch slightly rear ward of where they are supposed to be. Then rearrange whatever spacers you can on the chassis to extend the wheel base as much as possible. It might be possible for the chassis and body to meet in the middle - somewhere about 265mm, and it shouldn't be noticeable from a distance that the wheel base isn't quite correct for the body.
  19. Not having any experience with the M06, but having experience with aluminium steering upgrades in other cars, I'd say the Tamiya one will be a cut above the rest for one reason: the bearings will be better quality. If the ball bearings have slop, it partially defeats the purpose of upgrading to ball bearing steering. It might be cheaper to buy one of the other brands and replace the bearings with better quality ones if they are garbage, but often they are pressed in tightly to the aluminium part and may take significant effort to extract. Other than bearings, they are probably all functionally the same. At least that is what I've found with parts for other cars. They copy the attachment points from the Tamiya part, then make their own geometry for the rest of the part (to avoid copyright), which bears no impact on functionality as aluminium parts are rigid. Having bought aluminium parts from 4 of those manufacturers I'd rank them (in order of most preferred to least) 1. Tamiya 2. GPM 3. Yeah racing 4. Jazrider GPM and Jazrider are the same company it would seem, however GPM seems to be their premium brand.
  20. Got to test my weatherproof car after some heavy rain, and it worked spectacularly! Most of the chaos was contained at the ends of the car instead of being flung into the tub. Here's a second run, after the ground had dried up a fair bit
  21. Sounds like you need to calibrate your ESC to the transmitter. Check the setup steps in the manual https://www.mtroniks.net/download.asp?ResourceID=1947
  22. Finished the mostly-sealed tub TT-02 with some custom FRP side trays and some closed cell foam to fill the gaps and make a tight fit to the body. Oh and some stupidly overpowered weatherproof electronics of course (7.5t running sensorless + Hobbywing 8BL150 + 3S). Now i'm waiting for some rain so I can test if it actually works or if it's still just a fast bathtub
  23. The 6amp figure is based on absolutely no load (pinion removed or motor out of car), and while it is not the most accurate way to tune the timing it will at least get you in the ballpark (+/- 5 degrees). The most accurate way to set timing is with a dyno to measure peak power. A less accurate way is to measure lap times but this introduces a problem as you're always testing with the same gear ratio so you will arrive at the most optimal timing setting for your current gear ratio, but a different gear ratio and a different timing setting may actually be faster because adjusting timing adjusts not only power output but also the kv of the motor and kv can compensate for gear ratio. Putting any kind of wired multimeter in series with the battery will change how the system behaves under load as the resistance of a typical multimeter and leads on a 10A range is in the ball park of 0.1ohms. That may not seem like much until you realise that even a mild motor like a 21.5t brushless draws around 20-30A in it's power band. 30A*0.1ohm = 3V drop across the multimeter! Measuring the peak current while driving will be meaningless for tuning timing as it will just be as much current as your ESC and battery can muster when the motor is stalled i.e. when you punch it from a standstill, peak current will occur. This will likely be 80A+ for 21.5t on 2S with the punch turned up, which obviously does not work if you have a 0.1ohm multimeter in the circuit as the multimeter will drop a tonne of voltage and prevent 80A from ever being achieved. At 6A the multimeter is only dropping 0.6V which while not ideal is somewhat more managable and introduces minimal effect on setting the timing. Ideally you want a DC clamp meter, which measures the current going through a cable without needing to break the circuit.
  24. For bashing on asphalt? First things I'd buy are spare tyres as you will go through many. I don't see the need for a slipper in a relatively light, small tyre 1/10 car. Building the suspension to handle jumps is a compromise in an on-road car because by increasing the suspension travel and raising the car it will traction roll easily on grippy surfaces. Running a lower suspension and accepting that on jumps the chassis may smack the ground might work out better for you. I run my on-road cars around 15mm ground clearance and accept that the chassis will smack the ground every so often, or leap in the air if it hits a stone or sharp lip at speed. Not sure which dampers are required to achieve that ride height on an XV-01.
  25. I actually find front caster has a more profound effect on stability than toe. Positive caster will make the front wheels want to steer in the direction the car is travelling in so the car tracks straight, as long as the servo is not forcing them to steer off course. Some slop in the steering, combined with positive caster therefore makes a car track straighter. Unfortunately, caster is often non-adjustable on many models because the angle is built in to the plastic parts. Most 4WD Tamiyas have very little built in, and require modification to get more. Theoretically, toe in at both axles should improve stability and this is mostly true for 1:1 cars. Imagine the car is travelling down the road and the car starts sliding slightly on the pavement and rotates a little to the left (it's now facing a little towards the left gutter instead of directly down the road). Now the left wheels which were previously scrubbing slightly due to toe in are pointed perfectly down the road and no longer scrub, and the right wheels are pointed even further towards the gutter causing them to scrub even more than normal. The right wheels scrubbing gives a slight braking effect and skid-steers the car to the right, counteracting the slide. However, there is a second effect. If the car starts steering towards the left due to steering slop, a bump/pothole in the road or tyres ballooning and becoming different diameters, the car will experience a weight shift to the right wheels (which in turn causes bodyroll to the right). Now the right wheels experience higher grip than the left wheels and produce a stronger steering force to the left, than the left wheels produce to the right. This results in the respective axles independently steering to the left. If the rear steers to the left and the front axle does nothing, the car overall turns to the right, so toe in at the rear definitely helps stability. If the front steers to the left and the rear does nothing, this makes the problem worse as it causes the car to steer even further to the left, therefore in the case of weight shift front toe in can decrease stability if there is a significant weight shift across the wheels on an axle. That is probably why some people report that front toe out improves stability, instead of toe in. Personally my go-to setup for stability is toe in at the rear, zero toe at the front, and positive caster. Some toe out at the front seems to improve the aggressiveness of the steering, and might decrease straight-line stability slightly although to be honest I don't notice a huge change compared to adjusting rear toe or caster. If there is a lot of slop in the wheel hubs, you may need to slightly toe out the wheel from the alignment that you want, because any driven wheels will toe in under power. As above, servo and servo saver make a big difference too. If you can move the mounting point that the steering arm attaches to the servo saver/horn closer to the center of rotation (effectively reduce the length of the horn), the servo requires more rotation to give a certain amount of steering throw. This may reduce the amount of steering, but reduces the effect of a deadband/centering error from the servo. Some servos just have a large deadband, which is how much the input signal has to change before they actually command the motor to move. This stops them constantly hunting around and burning themselves out. You can test this by turning the steering to full lock and back to centre in either direction, and checking if the centre position is the same from both sides. A servo with a large deadband will stop significantly right of centre when returning to centre from the right, and left of centre when returning from the left. Making sure the steering is mechanically adjusted to center (remove the horn/saver and reinstall centered) with no electronic trim will ensure you have close to even throw to the left and right before adjusting end points. Finally, consider adding a steering gyro.
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