Jump to content


  • Content Count

  • Joined

  • Last visited

Community Reputation

433 Excellent

1 Follower

About nbTMM

  • Rank

Profile Information

  • Location

Recent Profile Visitors

1430 profile views
  1. The stall current will be well over 100A on a 4.5t motor. Peak power is made at about 50% of max rpm and 50% efficiency. So a motor that makes 480W of mechanical power at 8.4V will be using about 114A from the battery to do it (480/8.2/50%). Stall current or the current at 0% rpm will be twice that of 50% rpm - 114*2 = 228A. In practice you won't see that much current, because of the voltage drop of the battery and MOSFETs in the ESC. Perhaps you might see a burst of 140-150A. With a 3.0t motor (840W mechanical power on 2S), 150A esc and a decent 2S pack I've measured a peak of 165A full throttle from a dig in a 1:10 chassis. Most battery packs that fit in 1:10 car will have a meltdown if you ask much more than 100-150A continuous out of them. All battery packs that fit in a 1:10 car will have a melt down if you ask for 200A+ from them. The claim that a saddle pack can maintain 330A continuous is unfortunately hog wash. That's not really an issue because a little 540 or 550 size motor cannot maintain that kind of current for long either. You want to gear the car so that any kind of prolonged throttle gets the rpms up into the 75% of max rpm range where you're only drawing ~50A. If you have so much power that you can only really take short stabs at the throttle, that's also a valid way of preventing things having a melt down.
  2. What happens is that the nylon part is a smooth cylinder and is forced/friction fit over the threads. After you take the nuts off and on many times the nylon gets threaded grooves cut/pressed into it, so it no longer offers as much friction as when new. 243 is just blue/medium threadlocker as used for grub screws yes.
  3. Serrated are best but will chew up the plastic wheel over time every time you take them on/off. Nyloc nuts work well when new, but over time the nylon bushing wears so they eventually lose their grip. If you're using thick hexes the threaded axle may not even reach the nylon part so your only choice is to use serrated nuts or find shafts which have a longer thread. The nuts don't have to be RC-car specific. As above 1/10 RC cars are generally M4 nuts. Generic M4 serrated stainless steel nuts will work perfectly to hold on the wheels and are usually lower profile and may engage more threads than RC car specific aluminium nyloc nuts Whatever arrangement you use some threadlock like loctite 243 will help keep them on. Also if you put two tamiya spanners/wrenches together that will give you more leverage to really tighten up the nut. Do a spanner check after each run to check they are still tight.
  4. I glue mine with CA glue as nothing else will keep the tyres on 1:10 touring car wheels over 60kmh. When the tyres are finished I slice around the tyre sidewalls with a scalpel blade to remove most of the tyre, then tear off as much of the remaining sidewall and glue from the wheel as I can with some pliers. Most of the glue will crack away with pliers as CA glue is quite brittle. Then I mount the wheel to a long M4 bolt and put it in my drill press, running a file against it to remove remaining glue and rubber. The wheels will last about 3 sets of tyres this way before the wheel bead becomes too damaged or worn down to reliably hold new tyres on due to curbing the wheels when driving, or filing away old glue, or before the wheel spokes crack due to big accidents. Tyre foams can also be reused many times, until too many big chunks have been torn off them when removing tyres due to glue getting on them, or if they get destroyed during a tyre blowout. I've found it is better not to attempt 'peeling back' the tyre bead to apply glue, especially with fast setting CA glue as you may not get all of the bead seated back together properly before the glue starts to dry, leading to out of round tyres. Clean the beads of the wheels and tyres with alcohol before gluing. When using water thin CA glue just mount the tyre and let gravity and capillary action suck the glue into the bead. If you're worried that the glue isn't going into the bead because the tyres fit too tightly to the wheel you can pinch the tyre against the wheel at various locations with opposing fingers which should cause the bead to open at perpendicular locations and allow the glue to seep in while it is still liquid. Glue one side at a time and let the glue set for at least an hour before flipping them over and doing the other side. Leave them at least a day before driving.
  5. I wouldn't. My thought is that a lexan shell may get a bit tatty, but still 'works' after it has been ground against the pavement at high speed. Some of my shells have been cartwheeled and slid upside down at 80kmh+ multiple times, crashed head on into a kerb at 50kmh+ and besides a few tape repairs and some unsightly scrapes are still usable. Lego not so much - once the studs (or pin holes for technic) get jacked up it doesn't function how it is intended to anymore. Once he gets bored of RC or graduates from lego bodies, he will be disappointed that his lego is now worse for wear and can't build other things properly out of it. If you had some lego dedicated to building RC bodies I guess that would work and adds something else interesting to do with RCs, but it sounds like a more expensive endeavour to me than just replacing the lexan shell if it eventually becomes unserviceable. The main body shell on a Plasma edge should last for ages anyway. The spoiler not so much. You can just remove the lexan spoiler, or retrofit a solid plastic spoiler (e.g. from a Traxxas, or many other generic ones on ebay).
  6. The four 'prongs' on the side that accepts the crosspin have to be shaved down a few mm, then it fits a TT02 perfectly.
  7. Doesn't look that way on the protoform VTA wheels/tyres. Either the tyres are >64mm OD or the wheels are <50mm/1.9" OD, because there is no fake sidewall as far as I can see and they are significantly higher profile than 1/10 TC wheels/tyres.
  8. If the tyre is 64mm as per their spec, which is the same as normal 1/10 touring car slicks, the wheel must be smaller than a normal 1/10 touring car 50mm/1.9" to achieve that much sidewall. Normal 1/10 touring car wheels are equivalent to a 20 or 21" 1:1 wheel when used with most tamiya shells. Those VTA wheels look more like a 17" or 18".
  9. C ratings are marketing bs for the most part. All they really ascertain is that one pack with a certain C rating from a particular manufacturer isn't as good as another pack with a higher C rating from the same manufacturer. In the following link is some real world testing, showing that some batteries marketed as 70-100C can't even do 35C with a reasonable voltage drop, while the best packs around can do about 50C max. Funny that the four packs that passed the 50C test were rated 65-75C, and most of the packs rated >75C performed very poorly. Goes to show that most of the vendors trying to sell you a >75C pack either have no idea what they are selling or figure that they can pull the wool over the eyes of their customers. https://www.rcgroups.com/forums/showpost.php?p=42381735&postcount=7579 Turnigy packs seem to do consistently well in various 3rd party testing, and their Graphene packs are top tier in the above test. Venom and Gens Ace seem like good quality batteries from what I've seen, but are a little overpriced (at least in my part of the world). Maxamps and SMC are bottom tier rubbish with a lot of marketing hype - avoid at all costs. That said, unless you run a fairly 'hot' motor or are a super competitive racer, you don't need much C from your battery. Most RTR setups are lucky to demand more than 20C. That's why the more powerful RTR cars move to more cells and lower kv motors - it allows the manufacturers to put more power into a car without requiring more current from the batteries. So customers can put trash batteries in them without taking a large hit to performance or puffing batteries. On the other hand if you are running a 7000kV motor and 120A esc in your 1/10 touring car then a quality battery capable of 30C+ may help. A pack being able to perform at extreme levels, even if your car doesn't need it to, also speaks volumes for the ability of the manufacturer to source quality cells and manufacture the packs properly, which could lead to longer lasting and safer packs.
  10. The drawbacks of the TT-02 chassis become much less apparent on loose surfaces. I would just buy another, set it up with CVA shocks, raised ride height, sealed bearings, rally blocks, a fabric chassis dust cover and send it... Running the same chassis as your friend could also be more fun than running two different behaving chassis together.
  11. The ESC advertising literature and/or downloadable user manual will tell you what cutoff voltages you can program in to it. If it doesn't have the ability to program the cutoff voltage, chances are it is unsuitable for LiPos. Some ESCs have you set the cut off on a 'per cell' basis and automatically detect how many cells there by measuring the battery voltage at turn on. Other ESCs require you to set the overall voltage for the pack. Both do the same thing however as the ESC can only monitor the voltage of the whole pack, not individual cells. Setting the LiPo cutoff voltage is probably the single most misunderstood part of safe usage of LiPos. 3.0Volts is the absolute minimum you should ever discharge a LiPo cell to however if you have a 2 cell pack that does NOT mean that you should set your LiPo cutoff to 6.0V. This is because the cells in a multi-cell pack are never perfectly matched, so if you set the cutoff to 6.0V, one cell would be >3.0V and the other <3.0V which is no good. To understand what is a reasonable cutoff voltage you must first understand the relationship between voltage and the state of charge of a battery. It is non-linear and goes something like this: >4.2V - permanently damaged, possibly unsafe to continue using, dispose of battery appropriately. 4.2V - 100% charge 4.0V - 80% charge 3.8V - 40% charge 3.7V - 20% charge 3.6V - 10% charge 3.0V - 0% charge <3.0V - permanently damaged, possibly unsafe to continue using, dispose of battery appropriately. I would set the battery cut off to 3.5 or 3.6V per cell. So for a 2S battery you program your ESC cutoff to 7.0-7.2V or 10.5-10.8V for a 3S pack. As you can see from the above, once a cell dips below 3.6V, it is over 90% discharged anyway. This gives you about a 10% safety margin in matching between the cells in the pack, so if the pack advertises that it is 5000mAh but one cell happens to be 5200mAh and the other 4700mAh you will still be OK. When the ESC cutoff kicks in at 7.0-7.2V, although your underperforming 4700mAh cell will be lower in voltage as more % of it's capacity has been spent, it should still be above 3.0V. Most reputable brand packs will have cells matched to better than 10%. Setting your cutoff lower than that won't give you appreciably longer run time and greatly increases the risk of over-discharging and damaging one of the cells in the pack if the capacity of the cells are not matched to better than 10%. If you have a very powerful motor, this can cause the battery voltage to sag under load and prematurely trigger the ESC cutoff. If you consistently measure your pack at say 3.8V per cell after cutoff is triggered, then maybe you might (with caution!) set your cutoff 0.2V per cell lower to compensate. You should check the cell voltages at the end of each run to keep an eye on how your pack is doing as some cells decrease in capacity faster than others as they age. A perfectly matched pack may no longer be perfectly matched after you've cycled it 50 times. If you notice any cells getting lower than 3.2V by the end of the run, consider increasing your ESC cutoff voltage, or retiring the pack as the matching between cells is becoming too poor for the pack to be serviceable. Storage charge should be about 3.8V per cell, or about 40-50% charge. LiPo cells degrade/age faster when stored at 100% charge . Storing at 40-50% gives longer lifespan and reduces the risk of fire as there is less energy to fuel a runaway discharge event. It also leaves enough charge so that the pack can sit on a shelf for a long time (at least a year) before it self-discharges all the way to 0% and becomes unusable. A charger with a discharging function can be useful if you charge a battery and then decide later not to run it, or your car breaks down mid-run and leaves the battery mostly charged. Otherwise you can get away with a charger that has a storage function but can only charge - run the battery down in the car and then charge it back up to storage and put it away. I charge/discharge batteries just on the bench in the open but always supervised for the entire charge. My theory is that if it's going to smoke up on the charger it's better for me to notice it immediately a few metres away and/or set off my smoke alarm. Don't be lazy and store batteries completely discharged or leave them installed in cars. Let them cool for a bit if they are hot, then do a storage charge and put them away in a fire bag. It is however better to put away a completely discharged battery and do a storage charge later if you don't have the time to be supervising an immediate storage charge. The golden rule is never leave charging batteries unattended. Fire bags are not as good as you being there to pull the plug if things go bad.
  12. If it's for bashing I would stick with a sensored setup as they work better if you spin out and stop often. Sensorless systems will hesitate and cog every time you get going from a stop, and they freak out more if the car starts rolling backwards - most will just wait until the car rolls to a stop before attempting to power forward again. If you always keep the car rolling forward a sensorless setup can however be just about as smooth as sensored. For ESCs from Hobbywing the 1/10 scale sensored options are QuicRun 10BL60/10BL120 or one of the XeRun XR10 variants. The 10BL120 will be plenty fine for bashing with a ~7.5t motor. The extra features of the XeRun are really only necessary for racing. For motors stick to 3650/3652/3654 (a.k.a. '540') size sensored motors. Anything from Hobbywing, Surpass, Trackstar, LRP (to name a few) will be fine - just buy whatever is cheapest imo as sensored 540 motors are standardised so any brand motor will work with the hobbywing esc. The power the motor makes is inversely proportional to the number of turns/winds. Below 17.5t is a substantial increase in power compared to a silver can. Roughly: Silver can = 70Watts 17.5t = 190Watts 13.5t = 250Watts 10.5t = 320Watts 9.5t = 350Watts 7.5t = 420Watts 5.5t = 500Watts LiPo batteries will be necessary below 17.5t. Kv depends on the sizing of the rotor and how the motor is timed therefore a 7.5t motor from one manufacturer may have substantially different Kv to a 7.5t from another manufacturer, but they should be similar in power. Therefore higher Kv does not necessarily mean it is more powerful. Some manufacturers don't list how many turns a motor is so you may have to guess what it is based on similar Kv motors from other manufacturers or if a power figure is given in the datasheet for it. Keep in mind also that a silver can is effectively about 2500kV so if you don't change your gearing, a 5000kV motor is asking for the car to be driven twice as fast to avoid running hot. If you aren't altering the gear ratio and plan to run the car in confined areas, a 3500-4000kV motor might be a safer bet.
  13. I've modified this type of Traxxas slash cover for my TT-02s (cut and re-sewn to reduce the length). Would probably work well for a DT-02 too. https://www.amazon.com/Raidenracing-Chassis-Traxxas-Original-Non-LCG/dp/B072KZ57T7/ref=pd_sbs_21_t_1/144-4080382-9035843?_encoding=UTF8&pd_rd_i=B072KZ57T7&pd_rd_r=d2b62ca3-6a5c-40ee-9427-805fbee03c5d&pd_rd_w=1iL9c&pd_rd_wg=QOCVD&pf_rd_p=5cfcfe89-300f-47d2-b1ad-a4e27203a02a&pf_rd_r=X0HWS4F6DDZ03WGC3MW3&psc=1&refRID=X0HWS4F6DDZ03WGC3MW3
  14. With brushless power, RWD isn't easy to control on dusty or bumpy surfaces. If you give it too much throttle the rear can break traction and the car swap ends in the blink of an eye. FWD will tend towards understeer if you give it too much throttle so it is a little easier to manage. 4WD can go either way and becomes highly dependant on the differential setup. With a tighter (thicker oil/grease or lock block/spool) front diff it becomes more FWD biased, with a tighter rear diff it becomes more RWD biased. And then you even play with one-way differentials to achieve even more interesting handling traits.
  15. You can do a lot better for not much more. Look into Flysky/Turnigy GT5
  • Create New...