Jump to content

nbTMM

Members
  • Content Count

    299
  • Joined

  • Last visited

Everything posted by nbTMM

  1. 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.
  2. Kind of expensive for what it is. Gives me ideas for rigging up two arduinos and a servo to pan my GoPro though
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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
  11. 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
  12. 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
  13. 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.
  14. 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.
  15. 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.
  16. Just chop the ESC plug off and put a HXT 4mm on it, same as your battery. That's all I run as all my batteries are Turnigy/HK and 4mm is better than XT60 which is in turn better than deans, at least in terms of power handling. XT60 or Deans is safer because you can't plug two batteries together - HXT you can, so keep kids away from a pile of HXT batteries.
  17. I like to think that a lot of Tamiya's customers are probably quite happy to build a car as per the instructions and have it tear up and down their driveway or backyard at 20kmh with the silver can because what they are after is really a remote controlled model, not necessarily a 100kmh remote controlled missile like your average traxxas customer wants. If the build is enjoyable and it can navigate their backyard at any speed, they are happy. If you look outside of this forum, you'd be hard pressed to find mention of fragile gears in a TT02B or many other 'common' flaws of other Tamiya cars. If the customers aren't complaining about it, Tamiya is unlikely to address the 'issues'. On the contrary, Traxxas are constantly pushed by their customers to make ever increasingly unbreakable products. People make youtube videos of their Traxxas cars breaking after crash landing a 20metre high jump at 80kmh and all the comments are "OmG it iS SooOOO WeaK TrAxXaS SuCks!!111"
  18. Started enclosing the tub of this TT02 with some XV01 guards and some foam. The aim is to get it almost fully enclosed once the body is on to keep the dirt/water/stones out.
  19. Yeah those are fish eyes, which are caused by surface contamination that the paint won't adhere to. Maybe the IPA or tack cloth cleaning steps left some residue that the TS paint doesn't like, or it got contaminated with some other type of overspray. Building up a series of very light mist coats before spraying a heavier coat can also help.
  20. On this forum maybe. Outside of this forum I wouldn't be surprised to find that TT01/TT02 see 20-50x the popularity that they do here and eclipse the sales of everything previously mentioned combined, for one reason only; the bodys that they are bundled with. A huge chunk of Tamiyas market must come from people who just want say a Subaru WRX RC car, don't know what a Lunchbox or Grasshopper is, and probably never find out either.
  21. Yeah racing universals. The dog bone drive pins and differential outdrives/cups don't like the torque. They get worn down and bend. I've also had the grub screws come loose on a shaft twice which causes the pin at that end to slide out, first time it locked up the wheel/shaft solid, the car cartwheeled and snapped the shaft at the universal joint. Second time it just mangled the pin (car still ran, but I noticed a clattering sound) and I was able rebuild the shaft by grinding a flat on a new pin. Thankfully both pins on the shafts are just standard pins like wheel hexes use, which I have plenty of. I think the demise of the last shaft was that the dog bone end was able to pull out too far when the wheel drooped which makes it ride on the 'knife edge' part of the slot in the drive cup, causing excessive and uneven wear, making it vibrate more than normal which shakes the grub screw loose and mangles that pin too. I've now cambered the wheels so that the shafts are inserted into the cup as far as possible without bottoming out when the suspension is compressed, and stepped up from blue to red loctite on the grub screws which should hopefully solve that problem. The differential drive cups also see wear - Yeah Racing cups and the Tamiya ones that came with a TT02 Type S are not immune to being impressioned by the pins. Turning down the punch on the ESC would probably also help but I won't resort to that yet as popping wheelies is fun . Yes, should be good to go out of the box and give you plenty of maintenance free running when built with a ball bearing set. The issues mostly come when you start upgrading it to go faster than standard, or crash it hard. Even if you keep it 'stock', parts will eventually wear out or break, and no RC car is immune to that. Replacements are especially cheap right now for a TT02B because it is a very popular kit and most parts are plastic. If you break a plastic part you just purchase the relevant 'parts tree' for a few dollars, and then you have spares of everything else on that tree. The part numbers for everything are in the back of the instruction manual so you can just punch in the number of the part you need into ebay or your local hobby shop to buy replacements.
  22. Nice. If you're fighting stability try putting the standard upper front suspension arms in, but flipped upside down, which brings the upper suspension ball joint rearwards by a fair bit. That gives you a whole lot of caster in your front suspension which will make the steering self-centre strongly. Ideally you'll want to space up the tie rod ball joints on the hubs, because caster tilts the hub backwards and lowers the tie rod ball joint - you want to raise the ball back up to the height it was previously so you don't introduce bump-steer (wheel turns when suspension compresses/droops) due to the tie rods pointing downwards at an extreme angle. I use brass standoffs (like computer motherboards mount on), but you can also just get balls with a longer thread and add spacers/washers. TT02RRfront upper arms can't be flipped upside down without cutting some plastic away which makes them very weak and break (as I found out...). The inability to adjust camber is no big consequence for speed running, especially if only at the front as 0deg camber at the front and a little negative camber at the rear will give you handling that tends towards understeer rather than oversteer.
  23. If you're going for a TT02B, I'd build it first with a set of ball bearings and everything else as standard. The plastic links/arms/shafts/gears/steering that come in the kit will be absolutely fine to get you going. The standard plastic suspension of the TT02/TT02B is almost bombproof. The plastic suspension parts are actually more durable then the metal/carbon parts because they will flex instead of bending/snapping. The rigidity of the carbon/turnbuckle suspension parts will however give you sharper handling, it's a trade-off of durability for performance. You can always add hop-ups later as you desire, and as the plastic parts start to wear out. Putting bigger wheels or a more powerful motor will definitely demand an upgrade of the differentials to metal gears which is not a particularly cheap upgrade. Stronger gears are required with a more powerful motor for obvious reasons, but stronger gears are also required if you put larger wheels on with the standard motor, because when the car gets airborne and then lands whichever wheels hit the ground last are re-synced to the road speed through the drivetrain by the wheels on the ground and that can put massive loads on the drivetrain, especially if the wheels are large in diameter and heavy (= more torque generated). I've done both a powerful brushless motor (about 8x the power of the standard motor) and big wheels (+30% diameter, probably twice the weight of standard wheels) to a TT02B and pretty much immediately stripped the plastic differential gears. Since then it's got GPM steel differential gears front and rear, in addition to the steel propellor joints, aluminium propellor shaft and steel universal driveshafts it's had from day one. Even now, I can see the steel driveshafts are going to be a consumable item - every 5-10 battery packs they are going to require rebuilding or replacing. It would be much more economical to just buy a Traxxas Slash, but where's the fun in that? . I like the challenge of working out which combination of parts to use to keep it semi-reliable, and fixing it when it does break. My suspension is still standard plastic hubs and lower arms from the kit - it has taken a few heavy crashes and nothing has broken yet, maybe I'm just lucky. I suspect eventually I'll break a hub - only when that happens I'll consider upgrading to aluminium hubs. This is it - you can see how much it bogs down in the grass compared to asphalt: only about 35-45kmh in the ~2-3" grass compared to 60kmh+ on asphalt. A completely standard, brushed motor TT02B only goes about 20-25kmh on asphalt and has half the ground clearance, so it would probably wouldn't even move on this grass.
  24. TT02B would be my pick for on-road and a bit of mild off road action (short grass, gravel, dirt) - grass longer than 1.5-2" will have it almost stopped in its tracks with the standard wheels, ride height and motor. Buy some different wheels for on-road use so you don't wear out the spikes on the off-road tyres. It is reasonably durable, but still requires some restraint otherwise you'll be breaking parts - it is a low slung buggy that is designed to be driven tidily over relatively smooth terrain. Parts are cheap and plentiful though and there are zillions of hop up parts to keep you amused and slightly improve it's off-road capability. DT-02/03 and DF-02/03 might be slightly more capable off road, but parts availability is not as good - they are older designs and support is dwindling. Tamiya unfortunately don't really have any cars that are super rugged and super capable off road for all out bashing - that's not really their target market. Most tamiyas are really only designed to cope with a 'silver can' motor (low power brushed motor) and many parts are harder plastics which crack if abused. Newer designs (like the TT02B) have more flexible nylon and glass reinforced parts which cope with a bit more abuse. For all-out off-road bashing, I think you have to look towards ready to run cars from different manufacturers like a Traxxas Slash or similar cars from Arrma, Axial or Losi instead - those can take big motor power with relatively few upgrades, and many of those you could jump off the roof of a house and they would just shrug it off like it's nothing. If you aren't launching it off 1metre+ jumps you should be fine with a Tamiya.
  25. Took the TT02B out for a spin... was still running by the time the battery hit low voltage which was nice for a change
×
×
  • Create New...