Jump to content

nbTMM

Members
  • Content Count

    186
  • Joined

  • Last visited

Everything posted by nbTMM

  1. For me it's because i'm time-poor for running (need a commitment-free weekend, appropriate weather, daylight), but time-rich for building as that can be done most evenings. Also having what would seem like a virtually limitless budget to a kid, there's always the urge to continually upgrade/change what I've got instead of run it a hundred times over in the stock configuration as most kids would. I'll often hold off running a car because I'm waiting for a certain upgrade part to arrive.
  2. Fresh water generally does not bother sensorless motors or batteries as it not very conductive and batteries and motors normally deal with huge currents. They will not care that a few milliamps of current is flowing through some water when there are normally tens or hundreds of amps flowing through the main circuit. What will be a show stopper is if water gets into the low current circuits of the receiver, ESC, hall effect sensors on a sensored motor, or steering servo. When that happens you may find your car turning or accelerating out of control, or if the sensor system is effected the ESC could apply the wrong sequence to the motor causing the magic smoke to be released from motor, esc and/or battery. The problem with the sprays is that you can't always get it into the parts that matter. Better off fully dismantling the parts and applying epoxy resin to fully encapsulate the electronics. You'd probably also want to put dielectric grease into the sensor connectors in a sensored system.
  3. I don't think you can. I have the GT5 myself and the functionality of ch3-6 is extremely limited imo. The only 'feature' it has for the aux channels is for four wheel steering and even that is pretty clunky as you have to operate it via the scrollwheel/menu system. Maybe someone makes a steering controller that you can put at the receiver end to use an aux channel to adjust the D/R of the steering channel. I think of the GT5 more as a decent 2-channel radio with gyro, model memory and 4 bonus aux channels that have very basic functionality, rather than being a serious 6ch radio.
  4. Mine is 1310g without a body shell but with battery, a Turnigy Graphene 4600mAh shorty pack (206g). It's pretty much a stock type S but with the blue chassis (glass fibre reinforced but the same weight as black one iirc), 64dp gears, the blue alloy and carbon hopups you can see, a standard diff with lock block in front and an oil diff filled half way with 3000cst in the rear. Could probably slash a few more grams by changing the steel turnbuckles and screws to aluminium or titanium. I'm sticking with steel for now as i'm a newb and prefer it to be durable. Light weight body shells around 60-70g are common. Most tamiya body shells are 100-150g because they have very thick polycarbonate to make them durable.
  5. Adding to the above, you'll need to modify the spur gear cover (to fit a larger pinion gear) if you want to run a FDR below ~4.7, which will be required if running 21.5t and probably also 17.5t unless your local track is tiny. Adjusting the FDR is a lot more work than other chassis as the rear diff cover (and therefore suspension), as well as the spur gear cover and the motor itself have to be removed in order to change the spur and pinion gears. It is less work if you only change pinion gears, but if making a big change you will need to do the spur as well since the TT02 only allows limited adjustment before the motor body or pinion gear interfere with the chassis or propshaft. All the cover screws are threaded into the plastic chassis, so if you aren't careful you will strip out the chassis over time. Luckily the chassis is a cheap replacement part. Type S fixes most of the short comings with the 'standard' TT02 suspension. The main adjustments you will still lack is rear toe (fixed at 3deg), front caster (fixed at 4deg but can replace c-hubs to get 6deg), and droop screws - you will have to rebuild the shocks to adjust droop. The number of holes in the standard shock towers is also lacking in order to adjust ride height independently of spring/shock rate, and there are only 2 options for mounting the upper arm to adjust camber gain / roll center - the inner hole of which is just about useless as you get almost no camber gain (which was the main problem with the standard TT02). To be competitive you'll need a spool or very stiff front diff and a looser rear diff. You can achieve this using grease in the standard diffs however it is inconsistent as after some time the grease gets flung off the gears and the diff becomes looser. What you really want for TC racing is a spool/locked front diff and an oil filled rear diff. The standard diffs will leak if you fill them up with anything less than really thick oil (>200K cst). A decent oil filled diff with o-ring seals is expensive for a TT02 (hopup 54875). 3racing make a cheaper one but apparently it isn't very good quality - although I haven't personally tried it. Put a lock block in a standard front diff (not the tamiya one, it's too heavy) or simply epoxy glue all the internal plastic gears together, or run something like 1million cst silicone oil. You'll need to lower weight at every opportunity - light weight body shell, low profile servo, shorty/lightweight battery pack, minimise wiring lengths, carbon battery strap and front bumper mount - otherwise you'll find yourself at close to 1500g when other cars are running close to the minimum weight of ~1350g. A lot of the aftermarket aluminium hop ups will subtract more performance at a racetrack from being heavier than they will add from being stiffer than the standard plastic parts. The aluminium hopups that Tamiya offer are generally justified in increasing racing performance.
  6. I only ever rounded Tamiya turnbuckles when using steel wrenches. Changed to an aluminium wrench and no more problems. You want a wrench that is wide to distribute the force so if you don't get it on there perfect you don't end up with only 10% engagement between wrench and turnbuckle like what often happens with the thin stamped steel tamiya wrench. Poor engagement = rounding the part with the softer material, or both parts. You can continue using your rounded turnbuckles by filing flats onto opposite sides and using needle nose pliers to turn them, or file them down to exactly 3mm and use a 3mm wrench. Given that turnbuckles only cost a few dollars, I'd just replace them, then take the time to line up the wrench properly every time or invest in a better wrench to prevent rounding them..
  7. All in due time . Already feels way better than before, even with the cvas, probably because the standard tt02 suspension has so much friction damping "built in". The type S has very little due to all metal hinge pins, so the cvas are doing all the work . Makes me want to try retrofitting a standard tt02's lower arms with metal pins, just to see how much it can be improved.
  8. That's what ESCs with boost/turbo currently do. The endbell on a brushless DC motor (what RC cars have) just houses 3 hall effect sensors which are used to tell the ESC what the position of the rotor is, hence it knows when to switch the 3 electrical phases to the motor. Physically rotating the end bell makes the ESC think that the rotor is in a different position and hence retards or advances the timing of the electrical control. Physically rotating the end bell or simply adding or subtracting an angle in software achieves the same thing. So if you have 20 degrees boost starting at 5k rpm and ending at 20k rpm it's like someone is sitting there monitoring the rpms and seamlessly rotating the end bell up to +20 degrees as the rpms increase from 5k to 20k. On a 540 size BLDC motor you can widen the power band slightly and increase efficiency over that range by perhaps 10-20%. Not a huge difference but better than nothing. I think the point of the OP's video was more that they increased the efficiency above 85% for 20-100% of the motors usable rpm range, versus existing motors that are only >65% efficient over that range. Existing motors are already quite efficient once the motor is up to speed. Hence for stop start traffic the efficiency would be increased 20% or so by the proposed motor design. Of course, you could also just introduce a gear reduction so the motor gets up into it's efficient range at a lower speed, and sacrifice top speed, or add an automatic gearbox with more than 1 ratio. Reducing size, weight and cost of manufacturing is a big deal for 1:1 cars, so if something can be eliminated that's a very good thing, hence why most EVs run fixed gear ratios as the added weight, complexity and efficiency loss of an automatic gearbox isn't justified when you could just install more batteries instead. At the moment range is given more consideration than the actual efficiency of an EV. Tesla's Model S already operates with decent efficiency over a wide rpm range, and key to this is the use of an induction motor. It still has a fixed gear reduction however as the induction motor is built for much higher rpm than typical wheel rpms. Unfortunately, induction motors don't scale down in size very well, hence why no RC cars use induction motors (and I don't think many if any popular small 1:1 EVs). The motor in the smaller Tesla model 3 is a BLDC motor somewhat more like a really big RC car motor. The same problem as the Tesla Model S is true for RC cars, a little 540 size BLDC motor wants to spin at say 15,000rpm to make peak power when we only want a few thousand rpm at the wheels, hence a gear reduction is used. Making a small motor that turns at low rpm and produces a great deal of power on a low voltage isn't practical/possible. Similarly, efficiency at very low rpms (<20% of max rpm) is rarely a major consideration for RC. The tech in the video looks interesting but I doubt it will make it to RCs as it's too complicated for negligible gain in a racing context where you don't care if the power/efficiency band of the motor is somewhat limited. RCs are largely driven by controlled racing series, simplification, light weight and low cost. It's hard to beat what we already are running for that.
  9. What's better than having three TT02 chassis? Four, of course. I guess that makes this now a TT-02RR Type S
  10. 32dp and 64dp are so close to 0.8mod and 0.4mod that they might as well be the same so people used the names interchangeably. Where things go astray is that the preferred imperial size between those two sizes is 48dp and the preferred metric size 0.6mod. while both numerically divide the larger/ smaller sizes, they are not the same since the scales are inverse - choosing the number inbetween is like choosing halfway between 0.5 and 1 on one scale and halfway between 1 and 2 on the other, and 1/1.5 does not equal 0.75. Therefore 48dp and 0.6mod are incompatible as 48dp has finer teeth. 48dp is close-ish to 0.5mod and 0.6mod close-ish to 42dp, but not like 32dp/0.8mod and 64dp/0.4mod are. 42dp and 0.5 mod are not common, at least in the RC world. Naturally in the US they preferentially use the imperial names so some genius (moron) thought to market 0.6mod gears as "metric 48dp" so customers would have some idea about how big they were without needing to be familiar with the module scale.
  11. I don't think so. For V1 turbo you need this one https://hobbyking.com/en_us/turnigy-trackstar-turbo-and-waterproof-esc-programming-box.html
  12. Got some big boy shoes for the TT02B. I sense a lot of parts finding their mechanical limits in the near future. Worth it tho
  13. Yes, just needs longer turnbuckles. You can also just reuse the standard plastic tierods with the aluminium steering upgrade since the TT02B already uses 4.8/5.0mm balls for the tierods. That's what i'm doing and I don't see any point in upgrading yet since I have no desire to adjust the toe from 0 degrees. Like so (my aluminium steering parts are not tamiya brand but are functionally identical)
  14. How much can the universal shaft move axially in the hub with the wheel attached? If wheel/shaft can move in and out of the hub more than 0.5mm that's a problem because when shoved sideways it can shock load the bearings - if this is the case add shims between the universal shaft and inner bearing so there is only about 0.1mm movement. Similarly if there is zero movement, the bearings are preloaded which will cause premature bearing wear. If it's too tight with no shims, try sanding down the back of the wheel hex (or just try different hexes, they all have slightly different tolerances). And yes there is a big difference in the life of bearings due to their quality. I have had quality ABEC 7 rated bearings last 10x as long as cheap ebay ones, and i'm only paying 2-3x the price for them.
  15. What I don't like about the CS setup is that the throttle control isn't intuitive. At low throttle where the car is basically functioning as RWD, more throttle equals more oversteer. At higher throttle, more throttle equals less oversteer as the car reverts to a 4WD rally style drift with both front and rear wheels spinning significantly faster than the road speed. The other thing I don't like is that due to the CS ratio, the car seems to get 'locked on' to drifting around a circle that satisfies the CS ratio (front and rear wheels both having similar traction) and it is very difficult to widen the line that the car is taking without drastically changing the amount of throttle and therefore the speed of the car. You can see this in the following video when I was trying to drift a big oval around the two paint cans, it was really like connecting a series a equal radius arcs rather than drifting a continuous oval. I had some problems with the car getting 'stuck' in a slide also - I'd be on full lock and whatever I did with the throttle I couldn't get it to transition back the other way. I think part of this is due to having negative ackerman. It probably needs slightly positive ackerman so when the throttle is let off slightly it transitions into a slide going the other way. I think CS works well for effortless sliding around in a big area but for drifting a track with pin point accuracy I think a RWD setup will work better, so that will be where this build is headed next.
  16. Since a CS drift car requires more steering to prevent spinning than a 50:50 drift car, the steering has to be set up for greater steering lock. The standard TT02 setup is not suitable for two reasons. Firstly, it creates too much ackerman angle - i.e. when you steer to the right the right wheel turns a lot more than the left wheel. This creates a braking effect at the front of the car when drifting as one of the wheels isn't pointed in the direction that the car is travelling in. For 50:50 and CS cars with a small CS ratio this can be desirable as it promotes oversteer. For large ratio CS setups and rear wheel drive cars it's undesirable as the car will spin too easily. Secondly, when the inner wheel is turned, the angle between the steering hub and the tie rod becomes close to zero. Note how the red and pink lines are near 90degrees when pointed straight ahead, and near 0 degrees when on full lock: On full lock the steering has no control over the inner wheel and the hub will just flap around due to forces from the road. The tyre can rub the chassis resulting in an unintended braking effect and a spin. The solution is to change the geometry of the steering arms. I'm using these extended ones from active hobby. Additionally I'm using some home made aluminium brackets on the hubs which move the tie rod mounting point outwards and allow the tie rods to be a more reasonable length. They also dial out the ackerman from the steering, in fact a little bit too much as now I have slight negative ackerman; when turning right the left wheel turns a bit more than the right wheel. You can see how now the angle that the tie rods make with the hubs stays within about 45 and 90 degrees for all steering angles. When pointing straight ahead the angle is about 45 degrees so the straight line stability won't be as good as the standard steering, but it'll be much more solid and stable while drifting. For suspension up front i'm using standard hubs, standard lower arms (with steel ball hopup), a 5mm ball end installed on to the top of the hub and aftermarket turnbuckle upper arms with a 5mm rod end installed. I rebuilt the kit CVA shocks with 3-hole pistons, 700cst oil and red (soft) springs from the 53163 spring set. I drilled a new hole in the lower arm so I could attach the shock to the arm further in than standard. This creates a really soft suspension with really long travel. I want the suspension to react as slowly as possible as this should make the car easier to drift, and won't be easily unsettled by bumps in the road Front driveshafts are a combination of 3Racing SAK-X27 double cardan shafts and Yeah Racing adjustable rod ends (to shorten them appropriately). These don't 'clatter' when on lock like universal shafts do because they are a true constant velocity joint. Additionally they can't fall out like the TG10 cups and metal dog bones can. Top: TG10 cup, metal dog bone - standard parts from a TT02RR Middle: yeah racing universal shaft Bottom: double cardan shaft The steering servo is just a cheap metal gear turnigy one: 12kg, 0.18s. Solid aluminium horn for zero slop (and because I don't care much for this servo ). It's a slow servo, but faster is not always better for gyro assisted drifting. The slower the servo is, the more you can turn up the gain of your gyro (= more steering lock from gyro) without instability occurring. The rear suspension has the same super soft long travel shock/arm setup as the front, but with yellow (medium) springs from the same set, due to the TT02 having a slightly rear-biased weight distribution. Driveshafts are the TG10 style with metal dogbones as came with the TT02RR Hubs are some 3degree toe hubs (yeah racing iirc) that I cut and added M3 threads for 5mm balls to attach - not very well mind you, the balls need to be angled in to shorten the upper arms more and achieve more camber gain. Upper arms are from yeah racing's RWD conversion line, and the strut tower is a carbon one from Eagle racing - I don't recommend the latter, get the Tamiya brand one the fitment is a lot better. Suspension flex is more like a 1:1 street car For electronics I'm just using a TBLE02S and 2S LiPo battery. NiMH had plenty of power, but LiPo voltages remain more constant from fully charged to empty, which helps since drifting is sensitive to throttle control. NiMH would have you barely touching the throttle on a full pack and having to floor it constantly when it was almost empty. For the radio I'm using my Flysky/turnigy GT5 with inbuilt gyro. The GT5 gyro is a lot better than the cheap standalone GC301 gyro I tried previously. It steers much faster into a slide, but steers back to straight much more slowly. The result is that you can turn the gyro gain up way higher before the gyro becomes unstable (gyro starts swerving when trying to drive in a straight line). After driving this setup I changed the front diff to this eagle racing one which has the same gear ratio as standard (39t/15t), therefore dropping the effective CS ratio from 2:1 to 1.66:1 With the 2:1 ratio I either didn't have enough steering lock or enough driving talent to catch the slides
  17. Taking a break from the TT02B while I wait for some parts to arrive, so I started the drift build. I built this initially as a countersteer/'CS' setup where the rear wheels are over-driven and the front wheels are driven by a one-way diff. This sends drive to the front wheels only when the rear wheels spin a certain % faster than the front wheels, so it allows RWD behaviour up to a point. If the car slides past a certain angle or you floor the throttle you get 4WD which helps pull the car out of a drift and prevent spinning. Later I decided that this setup wasn't really what I wanted, but I'll show the build process anyway. Inspecting wear on the stock rear diff from 3S running. There is some, the teeth of the pinion are partially rounded over but it still ran well like this. Chassis fully stripped I'd stripped out the threads around the motor mount before and installed brass M3 inserts. Some of these had pulled out a bit over time due to removing and reinstalling the spur gear cover - they can be pushed back in with a soldering iron at 200*C. Chassis parts after cleaning with warm water, dish liquid and a paintbrush In the rear I used a steel geared eagle racing spool with 16t pinion and 25t crown gear, which gives a 66% overdrive compared to the standard 15/39t diff gears. The prop shaft needs to be modified to fit the Eagle pinion gear, as it uses a drive pin and an M3 bolt to hold it on to the end of the prop joint, instead of the flats which the stock gear uses. A spacer and a stack of shims position the diff pinion gear correctly. This isn't the best setup as everything presses down against the motor spur gear and its drive pin, which locks the spur solid on the joint. You don't really want this as some slop in the spur gear will allow for some misalignment between it and the motor pinion gear (which there will be some as it's a plastic chassis). The result of this is some additional noise from the gears, but it works OK. Up front i'm using a one-way diff for a HSP touring car with a set of plastic 42t/13t underdrive gears made by Active Hobby. The crown gear required the bolt pattern be redrilled for the rectangular pattern on the HSP diff center. The outdrives and bearings are from an Eagle Racing one-way. The combination of the under driven front diff and overdriven rear diff make the 'CS ratio' about 2:1. I.e. the front wheels aren't driven unless the rear wheels are spinning twice as fast. The standard plastic propshaft is used since it is fine for the low power For the motor i'm using a brushless Hobbywing Justock 21.5t. Gears are 64dp, 104t spur and 36t pinion. Together with the overdriven rear diff, the effective final drive ratio is about 4.5
  18. I think it's just down to bad/inferior firmware design more than anything. A lot of it's behaviours seem to me like corners cut in the firmware rather than intentional or because of a hardware limitation. The 120A GenII is sensored or sensorless and will happily change directions when the motor is still spinning at non-negligible rpm (probably several thousand rpm) in for/brake/rev mode. Also if the sensor cable is unplugged on the GenII it seamlessly transitions into sensorless mode (runs a bit rougher and turbo/boost gets disabled iirc). If the sensor cable comes out on the 80A turbo esc it just tries to fry your motor since it thinks that it's stationary so just continuously powers one winding. I can see how not being able to reverse until stopped would actually be a benefit on a race track, as you can have reverse available but never accidentally reverse when double-braking.
  19. Sounds faulty, I'd return it. I have a trackstar 80A turbo ESC and don't like it much. It does some really stupid stuff like you can't reverse until the car has actually come to a dead stop so if you're going down a steep hill and the brakes won't hold it's impossible to get it into reverse. Also if you're rolling backwards and try to accelerate forwards it holds the brakes until it comes to a dead stop and then goes forwards at maximum punch, regardless of your punch setting. Again, if the brakes aren't enough to stop it rolling backwards you'll never get it to accelerate forwards. I find the Trackstar 120A GenII ESCs much more polished and well worth the extra $. I've had zero issues with the two that I have.
  20. That piece that clips in under the prop joint can be omitted entirely. It's sole purpose is to limit steering throw as you've found out. The hubs and lower arms have stops on them as well which you can cut off to achieve more steering lock. If you remove all that it is possible in a crash for the tie rod to over-centre where it attaches to the hub, jamming the steering. You can just pop it back by hand, but it could cost you valuable track time. If you're using dog bones instead of universal shafts it is possible for the dog bone to be ejected when this happens also. Upper ball joint can be tightened with the steel ball hopup but money is better spent just changing the top arm to a 4.8/5mm ball joint and turnbuckle arm. You are right that wider track is better and it is worth trying to get as close to 190mm as possible. Should be able to fit 8 or 9mm hexes with the standard driveshafts if you use serrated wheel nuts (e.g. Tamiya #42282). The wheels will stay on securely with only 2 or 3 threads engaged on the nut because the serrations will bite into the plastic wheel and lock in place. The downside is that they chew up your wheels every time you take them on and off. The body being 200mm may be considered oversize - depends on your local club rules. Usually at a club level they will be more strict on the track width of the chassis than the actual body.
  21. Do it anyway? The wear is part of their story
  22. That probably comes more down to the chassis than motor power. Nitro or electric, if you have the will you can put enough motor power in a car to make it wheelie (or do a rolling burnout) constantly yet you never see anyone popping a wheelie down the entire main straight on a racetrack - having a car with that much power is just uncontrollable and not very fun to drive so it's either banned, or in the unlimited classes people just don't do it because it's not consistent enough to win races. The difference in lap times between foam tyre and rubber tyre cars is far greater than the difference between high turn rubber tyre and mod rubber tyre because both rubber tyre cars can only corner so quickly before they loose traction (or roll). The only difference in speeds is on the straights. With modern ESCs you can calm down the stall torque and increase the mid-top end torque which makes it have a powerband more like a nitro. I'm an 'electric guy' because the maintenance is far easier and running costs are lower - 'fuel' is virtually free, and electric does not need warming up, retuning of oily bits, doesn't disturb quiet neighbourhoods and doesn't care about atmospheric conditions - it'll make the same power rain, hail or shine. If you leave it on a shelf for 5 years it will still run like did the last time it ran. Instant torque makes it more usable in a smaller area - but can eat drivetrains.
  23. Not slow, but neither is 1/10 EP/TC mod on a big track, or 1/12 pan cars on virtually any track. I was more referring to bashers than on road racing though - if you're on throttle more than you aren't, it's slow Most sub-$1k nitro bashers are slow.
  24. Lol. I've never owned a petrol/nitro rc car but whenever I see one my first thought is 'holy cow that is slow'.
  25. If you do glue, drill air holes in the wheels (two 1mm holes or one 1.5mm hole should do) and add foams. With glue, but no foams and no air hole they'll be 'pumped up' so to speak and when one gets an (inevitable) air leak they will start behaving differently causing erratic handling. With an air hole, glue, and no foams they might collapse too easily under load.
×
×
  • Create New...