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nbTMM

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Everything posted by nbTMM

  1. They are so close (<1%) that they are effectively the same thing though. The teeth on small gears are not usually 100% accurate, they just have to be good enough. The cutting tools that create the teeth have a tooth range, so that one cutter may create the teeth on gears anywhere from 50teeth to 100t. It'll be perfect making teeth on a 50t gear but by 100t is considered just barely close enough - if you want to make a 101t gear you should get a different cutter. For that reason, the inaccuracy between two 64dp or 0.4M gears may be greater than between a 64dp and 0.4M. I wouldn't be surprised if in the industry people use the metric and imperial cutters interchangeably between similar pitches
  2. You can gain a millimetre by changing bearings. If the current setup uses 4mm wide bearings, use 3mm inners and 5mm outers. There may also be scope to grind the diff cup joints to get them to sit in a further mm. Otherwise, yeah racing make some adjustable universals for their tt02 rwd drift kit. The universals themselves are junk (aluminium) but you can use the adjustable dogbone ends on other shafts by cutting the shaft and grinding some flats into it. I used them to make short double cardan shafts for a tt02.
  3. Replaced the tub/deck on the TT-02 fun car with a blue hard one as the old black one was getting tired (screw holes wallowed out), then put these thin balloony rally tyres on it for a laugh
  4. A cap will definitely help prevent drowning out 27MHz radios with switching noise. With 2.4GHz radios it's less effective because the lead inductance between the brushes and motor terminals already kills most of the GHz noise.
  5. Red triangle or red arrow indicates a towing point. Blue triangle indicates battery location. Blue triangle with a red lightning bolt indicates battery isolation switch. Red 'E' is a fire suppression system pull handle
  6. Brushless aren't that much more efficient. Brushed hits about 70% efficiency, brushless is around 85%. The difference in ability of the ESC to handle brushed versus brushless motor comes down to what happens when the motor is stalled, or nearly stalled. Most brushed ESCs have no idea what the motor is doing so if you ask for full throttle and the motor is stalled, significant current will flow and the ESC might not do anything about it until it overheats or the battery voltage sags too low. The stall current of a 27t silver can brushed motor is about 70Amps, which the ESC will handle for quite some time before eventually overheating. Theoretically the stall current of a 13.5t brushless motor is about 250Amps. However, since a sensored brushless ESC knows how quickly the motor is turning (if at all) it can reduce the duty cycle of the pulses going to the windings to reduce the current. That's why you sometimes hear buzzing and clunking sounds when a brushless motor is turning against significant resistance, because the ESC is reducing the duty cycle of the pulses to manage the stall current and therefore it's capable of dealing with more powerful brushless motors than brushed.
  7. If it's a runner and you place more importance on longevity than shelf appeal, drill a small hole at the end of the crack to prevent it spreading. I just use clear packing tape on both sides of my running shells. When it gets ratty, remove clean and apply new tape.
  8. I think all of them are nylon, the parts tree will tell you; "PA" for nylon, "PA-GF" for nylon with glass fibre, "PA-CF" for nylon with carbon fibre. My experience with glass reinforced nylon is that the wear resistance is excellent - the grease or oil doesn't get polluted with dust over time like the cast aluminium gears do. However, since any plastic gear can still bend, if they get put under too high of a load the two gears can be forced apart and skip a tooth, and then small pieces of the teeth can break off.
  9. Try blowing an air gun into a open plastic bag, or under a sheet of paper held 1cm above a table. The effect is opposite to what you'd expect. The bag gets sucked closed, and the paper is sucked down onto the table. You can get the same effect with a flat bottom RC car, although I think the effects of dealing with the fact that the "inside" of an RC car shell is rather leaky (wheel arches and other gaps) makes much more of a difference than ground effects alone.
  10. You only 'need' to change gearing if the motor or ESC runs too hot. Otherwise, if you aren't racing it's a matter of preference. Less teeth will give more acceleration, more teeth will give higher top speed. If you labour the motor by gearing it for high speed and then running at low speed most of the time it will just run inefficiently, resulting in the electronics getting hot and the battery getting drained faster. A 15t brushed should turn about 30,000-35,000rpm if i'm not wrong. If the XV-01 standard final drive ratio is 8:1, at 100% rpm tamiya rally block tyres will be going about 59kmh. In reality, when actually under load you will probably only reach about 70-75% of maximum rpm so about 42km/h or so. If you put a 15t pinion in then you'd have a top speed of 30km/h and the car would accelerate faster and run cooler. I would order some other pinions to try anyway just in case it does run too hot on the standard pinion. There are cheap sets of 13t-17t 0.6 module pinions on ebay https://www.ebay.com.au/itm/M0-6-3-175mm-13T-33T-0-6-Module-Pinion-Motor-Set-Gear-For-1-10-RC-Car-Truck/333281900182?hash=item4d99263696:m:mzyWDetdZanYSm0Eigv8uHw&frcectupt=true Installing a 30mm motor fan will also definitely help keep the motor cool. Again, hit up ebay for "30mm rc motor fan" to find a cheap one.
  11. The quicrun 13.5t motor+esc combo is hard to beat for the price, I'd recommend that. TT02B needs at a minimum the metal differentials from a DF02 to be reliable as a basher, even with the stock brushed motor. A TT02B and Arrma Typhon are opposite ends of the spectrum for buggies. The TT02B being one of the most fragile and the Typhon being one of the toughest. If you want a TT02B to handle big power (<10.5t) and larger wheels than standard, expect to upgrade almost everything in the drivetrain.
  12. Well it looks like the previous black one was 27t with the timing advanced a bunch to bring the rpm up compared to a normal silver can. The new silver one looks to be 23t with mild or zero timing. Theoretically the new one should be a bit more powerful, but spin about the same rpm. It's likely that the new one is more of a generic motor so is cheaper to produce. Statically advancing the motor timing a bunch isn't usually done outside of RC because it makes the motor less efficient, so the black motor might have cost more to produce as it has non standard manufacturing.
  13. A 3-cell/'3S' (9.9V) battery will definitely make the car more powerful than a 2-cell/'2S' (6.6V) battery. Just make sure your motor and ESC are rated for 10.8V (fully charged voltage of a 3s life pack). The mAh rating is indeed the capacity of the battery - more capacity = more runtime. Be aware however than if you use a 3S battery, the electronics will draw more power so a 3S 4200mAh battery will have less runtime than a 2S 4200mAh battery. Higher mAh packs also tends to be heavier and physically larger, as will packs with more cells. The nano-tech pack is physically smaller, lighter and has lower capacity. I'd say the reason for the low discharge rate (1C) is because of the low-current plug installed on it. All batteries are inherently unsafe, as they can store a lot of energy, and if abused all that energy can be released suddenly resulting in a lot of heat and possibly a fire. LiPos are primarily less safe than NiMH because the energy density is slightly higher (mAh higher for same physical size) and they typically have much lower internal resistance, so will happily release a huge amount of energy quickly. A LiPo pack might happily provide 500-1000Amps of current if shorted out, whereas a NiMH might only do 50-100A. Lifepo and NiMH can cause fires, but you have to try much harder. Lipo and Lifepo are more sensitive to improper charging, over-charging, over-discharging and degrade more quickly when stored for long periods at an improper voltage compared to NiMH. LiFePo4 sit somewhere between NiMH and LiPo with respect to energy density, power delivery and therefore safety. Not sure what you meant by 'keeping stuff on charge isn't an option'? With LiPo you store the batteries at about 40% charge (~3.8V/cell), as this gives the longest shelf life and some buffer so the battery doesn't self discharge to 0% if storage long term (up to 1year). If a LiPo cell goes below 0% (3.0V) charge, it is permanently damaged and attempting to recharge it is risky. The car needs to have an appropriate cut-off so it stops before the battery voltage gets too low. Storing at 100% (4.2V) long term will also drastically reduce the lifespan of a LiPo. When it's time to use it you put it on the charger and bring it up to 100% which takes about 30mins to an hour for most batteries. All LiPo battery chargers automatically stop charging when the battery hits 100% (4.2V/cell). Balance charging is typically performed to make sure that all the cells in the pack are charged to equal voltage and no single cell is brought above 4.2v which could damage it. After use you should immediately charge (or discharge) the LiPo to the storage charge of 3.8V/cell and put away in a fire safe bag. Typically LiPo fires only happen if the battery is charged improperly (non-balance charger), charged or discharged at an excessive rate, or is continued to be used after being physically damaged or after accidental over-discharge. Because the risk is elevated when charging a lipo, you should never leave a charging lipo unattended. Technically Lifepo batteries should the treated the same as lipo to ensure maximum lifespan and safety, the voltages of interest are just 2.5/3.3/3.6 instead of 3.0/3.8/4.2. Using a Lifepo in a transmitter is somewhat at odds with the whole storage charge philosophy so I'm not sure how we ended up with lifepos being primarily sold for RC transmitters. I use NiMH in my transmitter. When treated properly and put in a fire safe bag while charging/storing, the risks of lipos are minimised. The exact same battery technology is used in phones and laptops, the only difference is that those batteries permanently have battery monitoring circuitry attached to them to prevent them being charged/discharged improperly, and people generally don't often crash their phones/laptops at high speed, physically damaging the battery. With RC batteries the responsibility is put onto the user to ensure that the battery isn't charged/discharged improperly and inevitably people get it wrong and cause fires. NiMH are generally much more tolerant of abuse (over charge, over discharge, stored at 100% charge) so are a better option if you don't have time or patience to charge/store batteries properly. They however self discharge at a much higher rate so you should charge them fully every few months to prevent them over-discharging while sitting on the shelf and degrading.
  14. nbTMM

    NiB

    I can't say that looking at a cardboard box ever gave me more joy than building what was inside and sending it down the road at 110%
  15. Repair and upgrade parts for some TT-02s, and Pro-line sand tyres to try at the beach this summer
  16. The silver kit motor is 27turns. The less turns a motor has, the faster and more powerful it is. WP-1060 brushed can handle down to a 12turn motor on a 7.2V battery. Depends what your definition of 'good performance' is as to if the kit motor will be adequate. A 12T is quite fast for most people - I would try the kit motor first, then upgrade later if you feel the need for more power.
  17. Silicone spray is just silicone oil mixed with a solvent in an aerosol can. It will achieve the same 'wet' look as rubbing silicone oil on the parts, but the solvent in the spray can attack the surface of certain types of rubber and plastic, making them appear milky or hazy when the silicone oil eventually wears off.
  18. It's a problem with the site. Happens on all browsers for me on my desktop, but if browsing from my phone it works fine.
  19. The normal TT02 is barely wider than 170mm with 6mm hexes and 24mm +0 wheels. Type S is just under 190mm with same hexes and wheels, and no way to adjust (afaik) so avoid it in this scenario.
  20. My understanding is that aerodynamics does not scale down perfectly due to how boundary layers act on scale wings and bodies versus 1:1 vehicles. Basically, wings on scale vehicles which are profiled like airplane wings do not work as effectively to create lift/downforce compared to their 1:1 counterparts. That's why you see Lemans/'Pan' style shells with a rear 'scoop' with aggressive attack angle, instead of a separate wing with shallow attack angle and a gap between it and the body for the low pressure zone to form. It's also why RC airplanes have to be extremely light weight or travel at insane scale speeds, because their wings are not very effective at creating lift. I think most of the downforce on an RC car comes from it simply displacing air, creating a high pressure zone above it, which pushes the shell downwards as long as the air inside the shell is lower pressure. A big scoop on the rear creates yet higher pressure over the rear of the shell as it increases the amount of air displaced, and therefore produces more downforce at the rear, at the cost of higher drag. If cut out the the rear of the shell, the low pressure zone generated behind the car will suck air out from the inside of the shell and maintain a low pressure zone inside the shell (or at least lower pressure than 'outside'), therefore maintaining downforce. Undertrays/diffusers/splitters on rc cars probably create less actual ground effect under the car and instead just act to better seal up the shell, preventing air from entering the shell and therefore allowing the low pressure zone at the rear to more effectively maintain low pressure inside the entire shell. If too much air enters the shell and too little air is sucked out the back, it becomes pressurised, creating lift and the car takes off.
  21. Patience has definitely paid off for me when selling niche items. It only takes 1 buyer to pay the price you want and they may not be looking at the time you create the listing, so you have to wait for them. I've listed and forgot about items, and then had them finally sell 3+months later. Offer postage otherwise you are dramatically reducing your pool of interested buyers. The automatic postage calculators on eBay etc work great for this so closer buyers get cheap postage yet you don't eliminate buyers who are really far away but prepared to fork out for the postage.
  22. Cutting out the rear of the shell so it doesn't act as a parachute and finding the balance between front and rear downforce so it doesn't take off like an airplane is going to matter a lot more than where the body posts are.
  23. Upgraded the TT-02 fun car to a Surpass hobby 3650 4 pole 5200kV motor. On 3S lipo, this makes for a healthy 1200W mechanical output power . Enough to destroy and blow fully glued tyres off the front wheels, because when the front diff unloads the inside wheel spins up to 150kmh+. Thicker diff oil required.
  24. If you use rubber tyres, making it rwd will just make it very difficult to control. With rubber tyres, as soon as the rear breaks traction the car will swap ends, faster than a steering gyro and lots of steering lock are able to react to. With the hard plastic drift tyres, things happen a lot slower so a gyro can sense the car rotating and start steering the wheels into the slide to prevent the car spinning all the way around. Money is better spent on a dedicated RWD drift chassis if that is what you want to do, instead of modding the TT-02 imo. If you want to give your TT-02 more drift happy on rubber tyres without converting it to RWD and making it almost impossible to control, try stiffening the rear diff by adding AW grease, and adding stiffer rear springs and softer front springs.
  25. Just disconnect the + wire from the second ESC, leaving ground and signal connected.
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