DeeMiller 1 Posted November 22, 2005 quote:Originally posted by Cactus_ze_bestHi, I love your project. I started a similar in august: A M-01 with a brushless motor. See it in my showroom. I install a Venom VSM but it doesn't work verry well. It show me the Km/h speed in the Mph display. So in 7.2V I made 46Mph (73.6km/h) Now I'm waiting for a Li-po 11.1V 4000mAh batt I'm starting a beetle M-02L opponent for this mini. It will have à 9x4 motor with an 8.4V batt. and a "no limit" ESC. Soon in my showroom id="quote">id="quote">Lol! Great stuff! Love these electronic devices! And no heatsink? There you go!(I mean GOOOOOO!) Maybe you could improve stability by reversing the middle chassis part so the battery is more to the rear (weight distribution). For the record: with a brushless motor it's more sensible to add a heatsink... But I already see some holes in it, does it have a fan inside? How's the temperature doing? I think it's more like HOW you drive it instead of WHAT you're driving. Compliments! That's why I use a modern RC-car to install these wonderfull electronic devices called ESC's and High Performance Motors. No way I would do that in a Countach or Porsche 935... Maybe one day, my Kyosho Dumptruck runs at >50km/h...(please stop me!) thanks guys for your input.[] Grtz Dee. Share this post Link to post Share on other sites
DJTheo 2 Posted November 22, 2005 quote:For the record: with a brushless motor it's more sensible to add a heatsink...id="quote">id="quote">Actually the opposite, as BL motors have very high efficiency (>90%) so dissipate very few energy as heat! [8D] quote:That's why I use a modern RC-car to install these wonderfull electronic devices called ESC's and High Performance Motors.id="quote">id="quote">Yes, M-02 is a very modern and high performance chassis [][}] LOL Btw if you replace the rear damper with the "torsion" bar you have installed you have replaced just the spring but not damping part, not good, as the rear will be bouncy... Cheers Share this post Link to post Share on other sites
Cactus_ze_best 0 Posted November 22, 2005 quote:And no heatsink?id="quote">id="quote">I will buy one for each with universals drive shaft soon quote:Maybe you could improve stability by reversing the middle chassis part so the battery is more to the rear (weight distribution). id="quote">id="quote">I will made a personnal middle chassis to fit on the original screws to center the weight and put the Li-Po inside. quote:For the record: with a brushless motor it's more sensible to add a heatsink...But I already see some holes in it, does it have a fan inside? How's the temperature doing? id="quote">id="quote">No fan inside It is not very hot. I mean 60° to 75°C quote:Maybe one day, my Kyosho Dumptruck runs at >50km/h...(please stop me!)id="quote">id="quote">lol I hope see a video of your "Alonso's Alpine F1" It's look nice. I think I will do something like your's on an other m-chassis. Share this post Link to post Share on other sites
mr_pushrod 5 Posted November 22, 2005 quote:Originally posted by DJTheoOf course forced air flow through fans is superior, that's why a passive (no fan) CPU or GPU cooler is much much larger then an active one. id="quote">id="quote">Very true as can be seen by the increase in the number of fan systems for cooling motors. An example of this would be the system available for the Associated TC4. Share this post Link to post Share on other sites
BiggusDitchus 38 Posted November 22, 2005 I really dont recommend a 13 turn motor, with decent batteries and the smallest pinion you are going to get extremely short runtimes, scorching hot motor and more than likely toasted batteries. I have from experience tried a 7 turn motor in an M03 to see how quick it was - Result was a less than 2 minute run time and a motor that was extremely close to unsoldering itself. A couple of other things that spring to my attention are.. "More pre-load on the spring, stiffer movement." - If you want stiffer action use a stiffer spring preload is for ride height adjustment! "Toe-in: app. +2 deg." - You are going to have one very tail happy car if by +2 you mean it has TOE OUT! If running a fast motor then you want it stable and recommend -2 deg. i.e. TOE IN! Why run a friction damper? If want a car to handle you want an oil shock that will DAMP the action of the spring, a friction damper doesnt dampen anything other than your enthusiasm to drive the car. Why do you think Oil dampers are hopups? Lastly PUT A HEATSINK ON THAT MOTOR! They are functional, they provide a larger surface area for the heat to dissipate, otherwise you WILL have the wires unsoldering themselves.. Advise listen to experienced comments People who have been there and done it. Please dont take these comments in the wrong way meant to help not hinder! One last point, to be the fastest M03 you will need a faster motor, as I pointed out at top of post I have run a 7 turn motor! Share this post Link to post Share on other sites
DeeMiller 1 Posted November 22, 2005 quote:Originally posted by BiggusDitchusI really dont recommend a 13 turn motor, with decent batteries and the smallest pinion you are going to get extremely short runtimes, scorching hot motor and more than likely toasted batteries. I have from experience tried a 7 turn motor in an M03 to see how quick it was - Result was a less than 2 minute run time and a motor that was extremely close to unsoldering itself. A couple of other things that spring to my attention are.. "More pre-load on the spring, stiffer movement." - If you want stiffer action use a stiffer spring preload is for ride height adjustment! "Toe-in: app. +2 deg." - You are going to have one very tail happy car if by +2 you mean it has TOE OUT! If running a fast motor then you want it stable and recommend -2 deg. i.e. TOE IN! Why run a friction damper? If want a car to handle you want an oil shock that will DAMP the action of the spring, a friction damper doesnt dampen anything other than your enthusiasm to drive the car. Why do you think Oil dampers are hopups? Lastly PUT A HEATSINK ON THAT MOTOR! They are functional, they provide a larger surface area for the heat to dissipate, otherwise you WILL have the wires unsoldering themselves.. Advise listen to experienced comments People who have been there and done it. Please dont take these comments in the wrong way meant to help not hinder! One last point, to be the fastest M03 you will need a faster motor, as I pointed out at top of post I have run a 7 turn motor! id="quote">id="quote">thanks, no offence taken and I know what you mean about taking advice. So toe-in +2 = "toe-out -2", right? What I mean is: "toe-in" means it's pointing inwards in relation to the driving direction. So a positive value means the wheels are pointing 2 deg inwards. I hope you understand what I mean. In RL racing, there's no such thing as "toe-out". It's only discribed at a value of toe-in...really. Example: toe-in -2 means the wheels pointing 2 deg outwards. Negative value on the toe-in means "toe-out". I get the impression that people think I'm stubborn. I'm sorry for that. I'm trying to prevent that...I'm only human. On the damper, I WILL use one, but I haven't had the opportunity to test all my modifications yet. Still, this kind of discussion helps me to rethink my ideas. Please don't take it personal, I'm only trying to put my ideas (good or bad) into reality. Grtz Dee. Share this post Link to post Share on other sites
DeeMiller 1 Posted November 22, 2005 quote:Originally posted by DJTheoquote:That's why I use a modern RC-car to install these wonderfull electronic devices called ESC's and High Performance Motors.id="quote">id="quote">Yes, M-02 is a very modern and high performance chassis [][}] LOL id="quote">id="quote">No need to be sarcastic as a moderator. Offence taken. Grtz Dee Share this post Link to post Share on other sites
mr_pushrod 5 Posted November 22, 2005 I would be tempted to run toe in on both ends of the car as this will add more stability. Aggressive turn in will just make the car harder to control (especially considering it is RWD only as well as make the car more liable to wander (the last thing you need at warp factor 9). Also, have you checked the timing of the motor? As I keep saying, this may need to be changed as the motor runs in reverse to the norm on the M02 and M02L. I'm sure no offence was intended by Theo, seemed to me like a light hearted joke! Share this post Link to post Share on other sites
terry.sc 16 Posted November 22, 2005 I would definitely recommend a heatsink for the motor, the motor is buried inside the car so there isn't any air blowing over it when running to help cool the motor. By fitting the heatsink you also have an extra layer between the motor and the plastic gearcase to prevent the gear case softening. As the M01/M02 heatsink is in two parts if you need to you can add a bigger heatsink from a PC CPU to the top. I would also suggest that to make it as stable as possible at speed the rear suspension should be softer than the front. If you want to keep the rear rollbar I would also suggest adding an oil damper on the rear, without the spring so it doesn't make it any stiffer. Share this post Link to post Share on other sites
DJTheo 2 Posted November 23, 2005 Sorry Dee, as mr_pushrod understood, i wanted only to continue your humour about 935, cheetah, dumptruck and wonderfull electrical devices, really didn't want to offend you, I like "different" projects. Cheers Share this post Link to post Share on other sites
DeeMiller 1 Posted November 23, 2005 quote:Originally posted by DJTheoSorry Dee, as mr_pushrod understood, i wanted only to continue your humour about 935, cheetah, dumptruck and wonderfull electrical devices, really didn't want to offend you, I like "different" projects. Cheers id="quote">id="quote">Apology accepted, Theo. In this context, it looked like sarcasm which I hate: it shows no respect. Leveling off now.[] Glad you like "different" projects: did you see my "High Performance Celica"? @All, thanks you so much for all kinds of valuable information! Btw, I got another story for you guys about the Acoms ESC (see seperate topic). Grtz Dee Share this post Link to post Share on other sites
DeeMiller 1 Posted November 24, 2005 quote:Originally posted by DJTheoquote:For the record: with a brushless motor it's more sensible to add a heatsink...id="quote">id="quote">Actually the opposite, as BL motors have very high efficiency (>90%) so dissipate very few energy as heat! [8D] id="quote">id="quote">This is what I meant: xxxxxxxxxxxxxxxxxxxxxx - no links to live ebay auctions please! []id="size1"> Curious about the final price... Looks sweet, doesn't it? The controller is also available at an seperate auction... Grtz Dee Share this post Link to post Share on other sites
Toykid 596 Posted November 24, 2005 Hi Dee, Your project looks great. It will be interesting to hear how the car runs without a rear damper and just the stiff spring set up you have designed. As some of the other guys have mentioned the big challenge in running hopped up M-chassis is the gearing in the gearbox. In-spite of the number of gears in the gearbox it is very hard to gear down sufficiently for low turn modified motors. As such it is had to gear low enough to prevent the engine getting too hot. Remember it is not the number of gears, but the initial to final drive ratio that is important. This ratio is not just effected by the number and size of your gears but also the size of your tires. You can gear a car down or up with smaller or larger tires. Your F1 tires will help here (and they look awesome). There also seems to be some differing opinions about motor technology. Without going into too much detail here are the broad-strokes of motor dynamics. Yes although a brushed motor is designed to run hot, they have an optimal temp and if asked to work too hard (geared too high for example) they get too hot and their efficiency drops. Heat is not just bad for your armature it is also bad for your magnets and brushes. If your motor is running too hot chances are your ESC will also start to overheat. Brush-less motors require less in the way of cooling because they are so much more efficient and as such less energy is wasted which normally ends up being converted into heat. Because of this a brush-less engine will run cooler and give you longer run times compared to an equivalent spec brushed motor. I have actually un-soldered my motor and warped the gearbox on my M04-L by running the motor too hot[] Heat-sinks cosmetic? - I am afraid not. Check out the number of drivers using heat-sink and powered cooling fans at this years IFMAR world champs. When you race at that level no driver I know will fit anything to their car unless they believe it will give them a competitive edge. Brushed or Brush-less heatsinks can help - keeping cool means faster longer run times. With all that said Dee I am really looking forward to seeing how the body looks on the car with those F1 wheels. Good luck with those first test runs and keep an eye on that motor temp! James. Share this post Link to post Share on other sites
DeeMiller 1 Posted November 24, 2005 thanks Toykid. And thanks for your support. It's an endless discussion, I know. Better a bit cooling than nothing at all. I got some more wild idea's: -Coolingfins on the pinion... That means a complete new design of the pinionwheel (and gearcover), but I don't have the tool to make it. It would look like a sort of ventilated brake disk with a pinion at the back which drives the second gear. That way, the heat generated by the rotor goes through the rotorshaft to the pinion. So cooling the pinion would be more effective than cooling the case. But it's just silly, I know. -Carbondioxide spraying through a small nozzle at the endbelt of the motor. Easy to get, light and small but then the motor wouldn't reach it's ideal temperature... Also a silly idea... But remember: it's more efficient to exchange heat by conducting than radiation (air between stator and rotor works as an isolator, not good) Anyway, I don't think I will be able to drive it this winter. Maybe indoors? It just popped up in my mind...yeah, that would be the solution: dry condition, nice temp, flat surface! Now I have to find a place big enough to run at top speed... The local gym? ... Grtz Dee. Share this post Link to post Share on other sites
XanderP 1 Posted November 24, 2005 On the subject of heatsinks does anyone have an opinion on these http://www.stellamodels.net/catalog/produc...roducts_id=1908 They look pretty cool but whether the work well... I am not sure about the quality of the fan but in principle it looks like a good idea. Share this post Link to post Share on other sites
DJTheo 2 Posted November 25, 2005 quote:You can gear a car down or up with smaller or larger tires. Your F1 tires will help here (and they look awesome). id="quote">id="quote">Have never had those F1 tires in my hands but don't they look bigger then the standard M-chassis 55 tires? quote:Yes although a brushed motor is designed to run hot, they have an optimal temp and if asked to work too hard (geared too high for example) they get too hot and their efficiency drops. id="quote">id="quote">Based on which physical law an electrical motor would run better warm then cold? Resistance increases and magnets get weaker with high temps, also if it was like that RC companies would make motor warmers like for tires. quote:-Coolingfins on the pinion...That means a complete new design of the pinionwheel (and gearcover), but I don't have the tool to make it. It would look like a sort of ventilated brake disk with a pinion at the back which drives the second gear. That way, the heat generated by the rotor goes through the rotorshaft to the pinion. So cooling the pinion would be more effective than cooling the case. id="quote">id="quote">If above were true pinions would get very hot and melt plastic spur gears. Reason it (luckily) isn't so are: a) Rotor axle is very thin to transfer much and fastly heat to the pinion. Rotor gets heated more on its perimeter as there are the windings and heat transfer to the inside is slow. c) Due to the rotation of the rotor heat gets dissipated more on the surrounding air as its a forced, like on a ventilator. Even if above was the case it still wouldn't be an efficient solution as a) The pinion is in a closed gearbox and the inside would heat up fastly and have no way to give the heat out. Rotatings fins would work as a propeller and slow the engine down. What is more efficient are rotating fins inside the motor can, many 550 sized motors have them, as they are torquey and not high rpm racing machines, as fins mean losses due to aerodynamic resistance. RC car design is pretty well understood in the past 15 years and everything is relatively optimized, so its hard to have a ground breaking innovation, motor can heat sinks, small ventilators and metal motor mounts seem the only way for now. As others said an alternative is brushless as its very efficient (no brush losses), also easier to cool down as its windings are on the stator and not on the rotor. Since you want to make just a speed record, I would recommend you the "KISS" prinicple http://en.wikipedia.org/wiki/KISS_principle, think of it like a dragster, simple and light and for a short run, the motor will forgive the overheating. Cheers Share this post Link to post Share on other sites
Toykid 596 Posted November 25, 2005 DJTheo, quote: Yes although a brushed motor is designed to run hot, they have an optimal temp and if asked to work too hard (geared too high for example) they get too hot and their efficiency drop. (excuse the bad English it should have read "and become less efficient") I did not mean to imply that motors run better hot, I meant that even when a motor is running under ideal conditions it will still get hot, well I should have said warm, and motors are designed to withstand this to a degree but they should not run too hot. Of course you are correct, heat is always bad when it comes to electronics. James. Share this post Link to post Share on other sites
DeeMiller 1 Posted November 25, 2005 quote:Originally posted by DJTheoHave never had those F1 tires in my hands but don't they look bigger then the standard M-chassis 55 tires? id="quote">id="quote">Yes, they are. That's why I use a smaller pinion (16T). The body will be slightly modified to fit the (front)tires in. Share this post Link to post Share on other sites
