Jump to content

nbTMM

Members
  • Content Count

    299
  • Joined

  • Last visited

Everything posted by nbTMM

  1. I don't think so. Heres the MSDS for the "DeSolvIt" Australians are familiar with: http://desolvit.com.au/MSDS - De-Solv-It ACW.pdf and heres the MSDS for the graffiti remover: http://pdfs.findtheneedle.co.uk/12125..pdf The primary ingredient in the UK one which makes it work as paint stripper appears to by Glycol Ether which is absent in the Australian one. The Aussie one is primary used for removing stubborn sticky stains, such as sticker residue, without damaging painted surfaces.
  2. On brushed motors the brake function on the ESC usually just connects the two terminals of the motor together. A motor can function as generator, it depends on the EMF voltage versus the voltage applied at the terminals. If EMF > terminal voltage it's a generator, if EMF < terminal voltage it's a motor. By connecting the motor terminals together, the EMF voltage is shorted out, current flows in the armature which causes a magnetic field which opposes the force of the wheels/gearbox back-turning the motor. The motor heats up due the current flowing in the armature. The braking force is dependant on the speed since EMF voltage depends on motor speed - at high speed there is a lot of braking force and when stationary there is no braking force - you can imagine if the motor was just sitting on the bench and you shorted it out nothing would happen ;). Stronger braking could be achieved on a brushed motor by applying voltage from the battery in the reverse direction, which would actually achieve regenerative braking and charge the battery. The problem with this however is that in brushed RC setups the ESC doesn't know which direction and speed the motor is rotating, so it is unable to perform that type of braking. If you needed to brake suddenly with a brushed motor you could manually apply reverse throttle. except that if the car then spun 180degrees you'd then need to manually apply forwards throttle to continue braking, otherwise you'd then be accelerating in reverse! On sensored brushless motors, since the ESC monitors the direction and speed of the motor, it can actually battery voltage in which ever direction of rotation is necessary to slow the speed of the motor, achieving very strong regenerative braking at any speed and both in forwards and reverse. Since the ESC doesn't know how fast the car is travelling, only how fast the motor is turning, it is still possible to lockup the wheels under braking since the ESC is just doing whatever is necessary to make the motor completely stationary! To prevent lockups you can turn down the braking force in your ESC settings or transmitter settings, or just be more careful on the controls . I'm not 100% sure about sensorless brushless setups although I suspect it depends on the ESC as to which braking technique it uses.
  3. 3D printed carbon fibre is not the same as carbon fibre pre-preg sheets such as those that many RC parts are milled out of. Infusing short fibres randomly into the plastic makes it stronger than plain plastic but it does not achieve anywhere near the strength as parts where woven carbon fibre with long unbroken strands has been impregnated into the part. All consumer grade 3D printers are fairly poor in terms of mechanical strength of the parts produced. It's inherent to the fact that when you dispense hot plastic on to cool plastic the resulting bond is relatively weak. So your 3D parts are either going to be more fragile or excessively heavy/bulky compared to factory injection moulded parts. If you are serious about making custom RC parts i'd look into a 3-axis milling machine and cutting parts out of carbon fibre sheet and aluminium. Probably have to invest at least $2k for something decent and at that point you ask yourself if it's cheaper to just buy premade hopups and pick a chassis that has decent aftermarket support. Either that or just spend hours making parts by hand with a dremel/files/drill/etc
  4. Medium Loctite 242 or 243 (same as 242 but with better oil resistance) is what you want to use. Sure if you tighten the grub screw with enough force and the stars align it may not ever come apart even without thread lock, but using thread lock really idiot proofs the process. I've never had a screw back out with blue thread lock on it, even ones that I purposely only did up gently, or completely forgot to re-tighten after adjusting. Also put some thread lock on the two screws holding the motor to the motor mount, otherwise they can work themselves loose with heat/vibration too. Really any time you have a metal screw going into a metal threaded hole/nut in RC stuff, thread lock should be used. Where one part is plastic and the other is metal, don't use thread lock. When a plastic-metal threaded connection becomes loose, it's time to replace the plastic part. You may need to step it up to red (high strength) threadlock to prevent screws loosening where they are subject to high temperatures or a lot of vibration/force. If you even need red thread locked screws out, just run it for a bit and take it apart when it's hot, or apply heat with a soldering iron. The blue (medium) should at least prevent screws backing out completely and being lost in almost all cases. I have purple (low strength) as well, and didn't find it to be useful - small screws still loosen with it over time.
  5. If you raise type S suspension to a useable rally height you will have heaps of positive camber to dial out. Probably enough that you have to look for shorter driveshafts. You will also need longer shocks to even achieve that ride height, since there is very little adjustability unlike the normal TT02 where you can flip the hubs upside down. The Type S / TRF has a reputation for breaking hubs, I'm not sure it is the best choice for rally.
  6. nbTMM

    LSD

    Putting some tamiya anti-wear grease on the gears will do what you want. The more grease you add, the greater the locking effect. After some time however the grease will be pushed to the sides of the diff casing where it no longer contacts the gears and the effect will diminish somewhat. The ultimate solution is an oil-filled differential which was recently released with the TT02RR, since the oil will always drain back down to the bottom the locking effect is more consistent. I believe the oil filled diff will be offered as a hop up with part number 54875 soon although if i'm not wrong all you need to seal a standard TT02 diff so it can be filled with oil are two O-rings which sit in a groove around the outdrives and a cardboard gasket between the diff casing halves. 54875 comes with the O-rings, gasket, metal gears and pinned outdrives which can't fall out once assembled.
  7. Yep, quite impressive although I'm not sure it is completely in the spirit of TT-only racing to replace so much of the car. There's something satisfying about modding the standard TT02's goofy yet bombproof suspension to handle better while still being able to shrug off 60kmh rollovers like nothing happened
  8. Retrofitted some XV-01 sway bars to a TT-02. Trying out similar spring rates front and rear with with a stiffer bar up front - previously had stiffer springs up front. Also gave it a quick speed run - not too bad for 2S
  9. Sway bars allow you to adjust the roll stiffness independently of pitch/dive, whereas changing springs alone adjusts both at the same time. Moving to softer springs and a stiffer bar may achieve the same roll stiffness as harder springs and softer/no bar and therefore the same cornering performance when moving at a constant speed. Although softer springs will slow down weight shift between axles during acceleration and braking. 1:1 handling physics is directly applicable to scale RC cars. What must be realised is that many suspension design decisions on 1:1 cars improve steering feel therefore the driver can tell when they are approaching the limits of the car and not push it too far causing a loss of control. A setup which results in sudden understeer or oversteer might be acceptable if there is enough communication through the steering wheel that the driver knows to back off before they push it too far. In RC, we don't have any steering feel since we are just observing the car in the 3rd person, so suspension changes which improve 'steering feel' are moot and suspension changes which cause sudden loss of traction are less desirable.
  10. Ball diff shouldn't make noise unless it is loose/broken. The noise a brushless motor makes when you turn it manually is called cogging. Typically you should only hear that noise while the car is moving under it's own power when it is going very slow - typically below 5-10% of top speed. Coasting at high speed should be smooth and not sound like the drivetrain is full of rocks. I would check backlash of the drivetrain by holding the spur stationary and attempting to turn the wheels. It should not slip or make a loud clunk when turned either way. Check that the new motor is mounted straight so the spur and pinion aren't angled relative to each other - gears will be noisier if they are on a slight angle even if you set the spacing correctly. Dust covers installed after setting the gear mesh may flex things enough to throw out the meshing - you may need to set the gear mesh slightly looser or tighter to mesh just right when the covers are installed. As a last resort, swap a totally different spur/pinion gear set in, even if it isn't the ideal ratio it would at least tell you if the issue is that or something else.
  11. Offset looks about right to me, it's the diameter of the 1/10 wheels and arches which is too large, a common problem.
  12. 2S LiPo (7.4V nominal) is 8.4V fresh off the charger. 6S NiMH (7.2V nominal) is almost 9V fresh off the charger. So you shouldn't damage your TBLE02S from overvoltage from a LiPo since a freshly charged LiPo is actually lower voltage than NiMH. The cutoff of the TBLE02S is 4.9V which is too low for LiPo, but if you're skilled with a soldering iron you can modify it to change the cutoff to 6.0-6.6V so the ESCs cutoff is LiPo friendly. http://laneboysrc.blogspot.com/2015/08/tamiya-tble-02s-mod-for-lipo-cut-off.html
  13. I've got Jazrider alu uprights which have taken some decent hits and they are fine. Eagle racing uprights are probably better quality than Jazrider. Given that the standard plastic uprights are renowned for breaking, I wouldn't put too much thought into the durability of aluminium ones - if they work for you then great, if they bend then they bend. The key is to maintain at least some give in the suspension - if everything is aluminium something will bend, or you'll break the plastic tub or strut tower. I have standard plastic lower arms and everything else is metal and haven't broken anything yet.
  14. Got my tt02 dialled in with modded hubs (short upper arm = dynamic camber/roll centre mod). Handles like it's on rails now!
  15. If you have to stick with tamiya parts installed 'by the book' then use the TT02RR arms as intended with 1-2deg negative camber dialed in front and rear and put a locking block in the front diff as that will give you straight line stability to make up for the lack of caster adjustment.
  16. It feels forced sometimes like it's just to get more views. Typical clickbait style youtube videos. A lot of the bashing/trashing videos degenerate into childish destruction, it gets old after you've seen 5-10 of them. I highly doubt he makes 1 mil a year. If his store is the one I think it is (has he stopped selling, I couldn't find a link?), then he only has 1500 odd feedbacks in the past year. If we assume that only 1 in 10 people leave feedback (conservative) that's 15000 transactions to make 1 mil in profit or 66 profit for each transaction. Most items sold aren't even that much, never mind actual profit. edit: in his video "A Day in the life an ebay Seller" you actually see his computer showing he has sold maybe 20-30 items in a day and he 'picks the bits he's sold and lines them up on his table' and it's mostly small stuff like servos and replacement parts. That is in the ballpark of my above estimate and certainly not turning 2700+ pounds or dollars or whatever profit a day. His profit figure is probably BS fabricated to try and sell his business course.
  17. The front upper arm has no caster built in at all which makes it impossible to drive a straight line over 20kmh imo. Caster gives you high speed stability by making the front wheels self-centre. By default there is no caster angle in the standard TT02 or TT02RR so the car will veer all over the place as it drives over bumps in the road. You get caster by moving the upper front suspension arm backwards and since the TT02 upper arm has an offset ball joint you can simply install them backwards to move the ball joint further back and get lots of caster angle. The TT02RR arm however has an extra tab which reduces fore and aft slop but also prevents mounting them backwards. You need to cut the tab off or grind away a part of the strut tower which significantly weakens either one - I cut the tabs on the TT02RR arms and broke an arm in half on the first impact. They are probably reasonably strong if used as intended but the car is hopelessly unstable at speed. As a stop gap, put the standard arms (also included in TT02RR) in, installed backwards. You lose camber adjustment but you get caster for stability and they will be very durable. Ideally, get aftermarket aluminium adjustable arms with steel turnbuckles and mount them backwards. The Type S suspension will handle way better out of the box as it gives you lots of camber gain - as the suspension compresses you get more negative camber and as it droops you get less negative camber (or even positive camber). This maintains the tyre flatter to the road when the body rolls in hard cornering. You get camber gain by having longer lower arms and shorter upper arms, and/or arms that are splayed out at an angle (mounted closer together at the chassis and further apart at the upright/hub). Type S has significantly longer lower arms. Standard TT02 suspension has no camber gain at all since the upper and lower suspension arms are parallel and exactly the same length. The result is the tyre contact patch moves to the shoulder of the tyre during hard cornering resulting in a reduction in grip. Some static negative camber (as possible with TT02RR/adjustable arms) will counteract the positive camber of body roll on the outside tyres, but now you have more negative camber than ideal (= less traction) in a straight line. If you made the upper arm significantly shorter on a standard TT02 you'd get a lot of camber gain but you'd also get a truckload of static negative camber and that will do more harm than good. edit: If you are keen, the standard TT02 suspension can be modified to have camber gain by moving the upper mounting point on the upright inwards and/or up by ~5mm or so. At the rear, I drilled and tapped a hole to mount a ball end in the upright and used an adjustable ball end arm. I used a ball with a long (8-10mm) threaded section so it engages some threads either side of the standard pin pivot hole. Like so: This gives camber gain as we have shortened the upper arm, and the upper arm is now angled upwards relative to the lower arm. Attempt the mod on the plastic uprights first if you're unsure (3deg hubs included with the TT02RR are kind of valuable, proceed modding at your own risk!). The amount of camber gain can be adjusted by adding or removing spacers to the ball end. At the front, the simplest way is to mount both the upper and lower arms with the height adjusting spacers and small washers near the head of the screws. Ideally you want adjustable upper arms at the front to set static camber too. Again, camber gain can be tuned by raising or lowering the mounting point of the upper arm to the upright by the use of spacers. Better yet is to move the mounting point inwards the same amount as the rear, this way we can make the upper arms significantly shorter too. I'm experimenting with an upright with a ball joint mounted like this: This also changes the steering axis inclination (SAI, aka King Pin Inclination) which introduces some other effects both advantageous and disadvantageous. The Type S suspension has a lot of camber gain but no SAI/KPI because the suspension pivots and steering pivot axis are separate by the use of a C-hub. Yeah racing make a RWD drift suspension kit that allows almost all these geometry adjustments but it requires you to run their longer adjustable aluminium lower arms and I don't think they would be durable enough for racing or bashing. Aluminium arms bend when subject to big impacts. The consensus seems to be that aluminium upper arms are OK but you want to stick with standard reinforced plastic lower arms for durability.
  18. I don't know how everyones TT02s are so heavy. Mine is barely 1300g ready to run - 4000mah lipo, trackstar genII esc with fan, trackstar 7.5t 540 size brushless, trackstar metal gear servo, shell, rubber tyres, and just basic aluminium hopups. Pretty sure none of the mounting points needed exist on a TT-02. No reason you couldn't retro fit it though with some DIY brackets and appropriate holes drilled in the TT02 arms..
  19. Its 80A continuous, 400A peak. It says it's good for 10T on 2S right there in the manual: "Brushed Motor Limit with 2S LiPo / 6S NiMH: ≥10T or RPM<30000@7.4V (540/550 size motors)" No, it will not not run a 10T motor at full stall continuously but that is not required for normal driving. All that is required is that the ESC starts pulse skipping or shuts off before it gets damaged in such a scenario. The motor will still probably overheat first: 80A*7.4V = 592Watts which is a lot of heat to get rid of. You will encounter the same scenario with a silver can and that is why you can get away with say a 30A continuous rated esc even though the stall current of a silver can is like 70A - as long as the ESC has the smarts to pulse skip if the current ramps up too high.
  20. "Hobbywing Quicrun WP Brushed Electronic Speed Controller For Rock Crawlers 80A" says that it will do 10T on 2S. I would think that a brushless motor and ESC would get much better battery life and run cooler at that power level though.
  21. Yep, it's 16/33T (Eagle racing 3717V2-126) versus the standard 15/39T. I've also got an Active Hobby 13/42T underdrive in the front which together with the rear overdrive gives a respectable 1:1.57 CS ratio. With just the underdrive (1:1.24 CS), standard gear diffs and standard lock (as much as dog bones will handle) it was pretty fun although did understeer a fair bit off throttle. Where you'd normally be doing a rally style drift with the wheels pointed straight ahead you'd instead be starting to countersteer. With both underdrive and overdrive gears it's now undriveable - not enough lock to catch the slides and it understeers atrociously off throttle as the front wheels lock up hard under braking relative to the rears. I've got universal shafts, a front one way and big angle steering kit on the way which should sort that. Unfortunately the gears are kind of expensive and require mods to fit at both ends (underdrive gear needs redrilling to fit a one way centre). Eagle racing do have some stronger overdrive spools to give you a decent CS ratio with the standard front gears although this makes the rear gears pretty small and I don't know if those small gears would wear quickly. With the combination of under/overdrive gears at least there are decently sized gears at both ends. Eagle spools: http://www.broadtech.hk/eagleshop/shop/ShopProduct.aspx?type=Search&amp;keyword=3717V2
  22. Bearings and CVA (oil filled) shocks are definitely the first 2 things to get if you don't already have them. Mount the front upper suspension arms backwards which gets you about 10deg of caster which will help with high speed stability. If using the standard fixed length steering links you may want to add a spacer between the arm and front upright since the upright is now tilted backwards and this will introduce some toe. There are some plastic spacers that are perfect for this included as spare parts with the CVA shocks. You'll need a longer screw to account for the spacer - M3 screws will thread into the standard plastic holes if you don't have tamiya screws in the correct lengths. Grease the plastic balls in the front suspension arms to prevent wearing the balls out (instruction manual doesn't indicate to put grease on them). Adjustable (turnbuckle) upper suspension arms will give you camber adjustment front and rear. A little camber (~1-2 deg) will give you more grip around corner but less grip on the straights, and possibly some uneven tyre wear. The standard plastic lower arms are fine. Cut the bump stops off the rear uprights and lower arms (little rectangular tabs near where the parts meet) to allow the wheels to droop lower and stay in contact with the ground over big bumps. Add some 5mm shims and aluminium wheel hexes (the type with a grub/set screw) to remove the wheel axle slop and make them run true - plastic wheel hexes often result in wobbly wheels in my experience. Hexes with the grub screw also don't annoyingly fall off with the axle pin when you remove the wheels. If the diffs have side to side movement then 8mm shims will sort them out - the standard plastic gear diffs usually don't need this. Experiment with AW grease in the gear diffs. For a road car put lot of AW in the front diff and just a tiny bit in the rear diff. For a drifter do the opposite. You can just swap the entire diff assemblies front to rear to change the cars handling once you have them AW'ed. Front universal drive shafts will allow more steering lock. You can cut the lock stops off the front uprights and front lower suspension arms to get more lock, however this will make it easier to break things if crashed. One last thing which I don't think the manual mentions is to put some thread locker (e.g. loctite 243) on the screws holding the motor to the motor mount. Otherwise they will come loose over time and that will cause your spur and pinion gears to get chewed up. Some loctite on the servo screw will also be needed if you have a servo with a metal output spline.
  23. Fitting an Eagle Racing overdriven spool into a TT02. Standard prop joint is too short for the keyed end to seat into the new pinion gear and the sleeve on the gear was too long to fit inside the diff compartment. Solved by adding set screws (made from M3 bolts) to grab on to the flats of the joint, and 'lathed' the sleeve down to the correct length using a cordless drill and a dremel. Working great so far
  24. To compare motors, first you have to understand how they generate torque versus rpm. The following will allow you to compare any two motors if you know the number of turns, stall current (at a given battery voltage) and Kv for each motor. When the motor is stalled, the torque generated can be compared by multiplying the stall current by the number of turns. The stall current will be higher for a lower turn motor (of the same size/series) because less turns has less resistance so when connected to a battery a higher current flows. However, if there are less turns in a motor there needs to be a higher current drawn to produce the same torque as a motor with more turns. This is because torque is produced by the electromagnetic field of the windings acting against the field of the permanent magnets. The field produced will be stronger for a given current if there are more turns. We can compare some motors from the same series, just with different turns to find out the difference in torque when stalled: Motor -- Stall Current (@ 7.4V) -- Stall Torque (arbitrary units) Trackstar 21.5T (1855Kv) -- 22A -- Stall Torque=22*21.5=473 Trackstar 13.5T (3040Kv) -- 36A -- Stall Torque=36*13.5=486 Trackstar 10.5T (3730Kv) -- 45A -- Stall Torque=45*10.5=472.5 As you can see, there is no significant difference in stall torque between the motors with different number of turns. The advantage of higher stall current in a low turn motor is negated by the disadvantage of having less turns. However, since the stall current is significantly higher for the motors with less turns, the voltage drop caused by the battery, ESC and wiring will be higher and this will cause slightly less torque to be produced since the voltage at the motor will be less. Well, what about when the motor is not stalled? Here's where the Kv of the motor comes in to play. The reason a motor with less turns has higher unloaded rpms is because of back emf. When a motor is turning, the windings rotating in the field of the permanent magnetic cause it to simultaneously act as a generator. This produces a back emf voltage - a voltage which is opposite in polarity to the battery voltage and reduces the effective voltage applied to the windings and therefore reduces the current through the windings. The faster the motor spins, the greater the back emf voltage. When the back emf voltage equals the voltage applied at the motor terminals, the effective voltage is zero, so the torque becomes zero and the motor will not want to spin any faster. If there are twice as many turns, the back emf voltage will be about twice as much for the same rpm, therefore a high turn motor will fall off to zero torque at a lower rpm. The Kv is the number of rpms that the motor will produce per 1volt of terminal voltage with no load applied to the output shaft. Torque will reduce linearly from the stall torque to zero torque at the unloaded rpm. Using this, we can work out the torque at a given rpm. Lets use 1000kV as an example for the same motors: Motor -- Current @ 1000kV, 7.4V -- Torque @ 1000kV (arbitrary units) Trackstar 21.5T (1855Kv) -- (1-(1000/1855))*22A=10.1A -- Torque=10.1*21.5=217.2 Trackstar 13.5T (3040Kv) -- (1-(1000/3040))*36A=24.2A -- Torque=24.2*13.5=326.7 Trackstar 10.5T (3730Kv) -- (1-(1000/3730))*45A=32.9A -- Torque=32.9*10.5=345.5 And also for 1855kV which is as fast as the 21.5T will go: Motor -- Current @ 1855kV, 7.4V -- Torque @ 1855kV (arbitrary units) Trackstar 21.5T (1855Kv) -- (1-(1855/1855))*22A=0A -- Torque=0*21.5=0 Trackstar 13.5T (3040Kv) -- (1-(1855/3040))*36A=14.0A -- Torque=14*13.5=189 Trackstar 10.5T (3730Kv) -- (1-(1855/3730))*45A=22.6A -- Torque=22.6*10.5=237.3 So as you can see, even if a higher turn motor produced more torque, it falls off much more rapidly as the car gets moving. When the 21.5T is completely topped out, the lower turn motors are still making a useful amount of torque and will keep accelerating. Basically, all things considered equal (same battery, esc, wiring, gearing, etc) a higher turn motor MAY deliver slightly more torque at very low speeds, however a lower turn motor will deliver much more torque in the midrange and top end. If you then change the gearing to suit the lower turn motor it will be absolutely game over - a low turn motor will then deliver much higher torque everywhere from stall to top speed. If we consider that the Kv of the 10.5T is about double that of the 21.5T, when we change the gearing to suit the 10.5T it will produce about double the stall torque as the 21.5T with the original gearing. One thing not to forget is efficiency of the system. If the motor current is significantly higher then the motor will get significantly hotter, as will the ESC, and battery life will be much reduced. Motors run most efficiently at 75-80% of their unloaded rpm, so if you change to a lower turn motor and labour it (run it at too low of an rpm) everything is going to run blazing hot. Not much point putting in a lower turn motor if you aren't going to change the gearing and cause it to overheat and chew batteries - or, if you change to a lower turn motor but leave the gearing the same you need to run the car at much higher road speeds to keep the motor and electronics happy.
×
×
  • Create New...