Jim Posted January 20, 2015 Posted January 20, 2015 I am working on a full RC version of the 42039. In LDD I am trying to figure out the best motor setup, regarding motor positions, power, speed, etc. Bruno's Ferrari 458 Spider uses two motors to drive the car, so I figured; why not use more or less the same setup. For more torque I can swap the green and red gears, gearing it down a bit. My question is; how acceptable is a solution like this? It's probably better to use a diff, because the motors can spin at slightly different speeds. But practically; how good or bad is this solution...on a scale from 1 to 10. PS don't look at the motors not being properly connected, beams not properly braced etc. I am just interested in your opinion of the gearing mechanism. Quote
aol000xw Posted January 20, 2015 Posted January 20, 2015 IMHO using a diff coupling two motors that are pretty much the same is a waste of space and weight and adds friction and failure points. Your solution looks well braced also, so no grinding. A 10 I'd say. Quote
JGW3000 Posted January 20, 2015 Posted January 20, 2015 Madoca's corvette, which I am building, uses more or less the same set-up, two L-motors geared together, should work fine. Quote
Milan Posted January 20, 2015 Posted January 20, 2015 (edited) You dont need diff between motors. If both Ferrari and 42039 are somewhere similar weight, and you are satisfied with Ferrari performance using this setup, then I would say this is ok. As JGW said, Madoca is using similar setup, and car is working great. Although, you wont get that smooth acceleration and deceleration with regular gears. Edited January 20, 2015 by Milan Quote
Jim Posted January 20, 2015 Author Posted January 20, 2015 The Ferrari uses the XL motors powering even bigger bevel gears. I need to test this setup. Currently the speed coming from the motor matches the speed delivered to the wheels, so it's 1:1. (there's gearing up and gearing down) When I switch the two red gears on the L motors for two the smaller green version, it gears down twice, delivering more torque. Great to hear that this setup will work. Quote
Alasdair Ryan Posted January 20, 2015 Posted January 20, 2015 This setup is how my loader works too,it would be nice if you could squeeze in a small gearbox as well (manuel). Quote
Jim Posted January 20, 2015 Author Posted January 20, 2015 I think there might even be room for a powered gearbox. Nice idea I will make version 1.0 of the chassis without gearbox and go from there. Quote
DrJB Posted January 20, 2015 Posted January 20, 2015 (edited) Not only this is a valid setup, but it is also 'approved' by TLG. In the power puller, instructions call for using two motors in parallel in a manner very similar to what you've shown. Granted, the two motors will want to spin at slightly different speed, but they all have small variations in their torque-rpm curves and for sure will be happy spinning hand-in-hand, so to speak. Edited January 20, 2015 by DrJB Quote
allanp Posted January 20, 2015 Posted January 20, 2015 You could also use 3 16t gears for a half way ratio. Quote
PROlego Posted January 20, 2015 Posted January 20, 2015 (edited) Or two 24t and one 8t for full speed and less torque than a broken micromotor. The problem is that I think that needs a bit more space so teeth do not touch the liftarms. I've heard something about a slighty redesigned 24t gear that fits in that small gap without touching the liftarms. Edited January 20, 2015 by PROlego Quote
DrJB Posted January 20, 2015 Posted January 20, 2015 Personal Choice: If this is to remain a race-car, I'd stick with speed over torque, unless you want to make it into a crawler (then torque takes over the priority). Quote
Blakbird Posted January 20, 2015 Posted January 20, 2015 If putting two motors together in parallel, XL are the best idea. The reason for this is that if one of the receivers loses a signal for some reason, one motor will backdrive the other. XL motors can be backdriven quite easily without damage, but other motors may not fare so well. Quote
Jim Posted January 20, 2015 Author Posted January 20, 2015 If putting two motors together in parallel, XL are the best idea. The reason for this is that if one of the receivers loses a signal for some reason, one motor will backdrive the other. XL motors can be backdriven quite easily without damage, but other motors may not fare so well. That's something to consider. Thanks for the tip. I have been thinking about two XL's as well, like Bruno's Ferrari. However, two L's fit nicely in the inner area of the chassis. Eventually I want to use two SBricks. So it's probably best to connect the motors to the same receiver, to minimalize the chance of backdrive? On the other hand; I am probably going to use two rechargeable battery boxes, one for each drive motor. Personal Choice: If this is to remain a race-car, I'd stick with speed over torque, unless you want to make it into a crawler (then torque takes over the priority). Check! You could also use 3 16t gears for a half way ratio. I might try that as well. Quote
BrickBuilder7622 Posted January 20, 2015 Posted January 20, 2015 Very nicely done! I admire those that are able to use gears and wheels and the like so well as I am accustomed to building with regular bricks, but I daresay you have quite the awesome build here. :-) Quote
Epic Technic Posted January 21, 2015 Posted January 21, 2015 It's fine to couple two motors without a diff. I very often couple 3 L's and nothing bad has ever happend. Quote
Jeroen Ottens Posted January 21, 2015 Posted January 21, 2015 On the other hand; I am probably going to use two rechargeable battery boxes, one for each drive motor. Don't you run the risk that the two batteries will deliver different voltages --> different power/motor (I don't think it will give a different RPM per se, but I could be wrong) --> more stress in the construction? I'm not an electrical engineer, so maybe one of them can chime in... Quote
Jim Posted January 21, 2015 Author Posted January 21, 2015 Very nicely done! I admire those that are able to use gears and wheels and the like so well as I am accustomed to building with regular bricks, but I daresay you have quite the awesome build here. :-) Thanks.....but no thanks hehe. This actually is the chassis of the 42039 24 Hours Race Car. I must admit the chassis is pretty solid, like the rest of the build. I am rebuilding it in LDD and modding it to be RC. It's fine to couple two motors without a diff. I very often couple 3 L's and nothing bad has ever happend. Cool! Don't you run the risk that the two batteries will deliver different voltages --> different power/motor (I don't think it will give a different RPM per se, but I could be wrong) --> more stress in the construction? I'm not an electrical engineer, so maybe one of them can chime in... Well, that's actually something I need to study. I am not very familiar with how many motors per battery box, per receiver, per SBrick, etc. Guess I need to take some time to find out. Is that kind of information on Philo's page as well? Maybe there's a rule of thumb...feel free to enlighten me. The easiest way would be to put the two motors on the same output of the IR Receiver/Sbrick and connect it to a single battery box. Using a single battery box means I have extra space for the motor switching the gear box. 2x L Motor (or XL) for driving 1x Servo for steering 1x M Motor for hood/bonnet 1x M Motor for the doors 1x M Motor for the gearbox (optional) 2x LED You don't use most of the motors while driving, but I guess this is a pretty heavy setup for a single battery box? Or isn't this going to be a problem. 2 LED and 2x L (or XL) are running constantly. Servo and Gearbox occasionally Doors and Hood only when not driving Quote
TheItalianBrick Posted January 21, 2015 Posted January 21, 2015 2x L Motor (or XL) for driving 1x Servo for steering 1x M Motor for hood/bonnet 1x M Motor for the doors 1x M Motor for the gearbox (optional) 2x LED You don't use most of the motors while driving, but I guess this is a pretty heavy setup for a single battery box? Or isn't this going to be a problem. 2 LED and 2x L (or XL) are running constantly. Servo and Gearbox occasionally Doors and Hood only when not driving it is a bit heavy for one single battery box although you are not using all of them at the same time! Bytheway with gearbox what do you mean? the functions gearbox or the gears gearbox? Quote
Jim Posted January 21, 2015 Author Posted January 21, 2015 it is a bit heavy for one single battery box although you are not using all of them at the same time! True, only driving and steering at the same time...and the occasional gear shift. Bytheway with gearbox what do you mean? the functions gearbox or the gears gearbox? The functions gearbox has become obsolete. I am using an M-motor for each function. So it's the "gears gearbox". Quote
Captainowie Posted January 21, 2015 Posted January 21, 2015 The answer is, as is so often the case, "it depends". Your limitation is on current draw, which depends far more strongly on motor load than which motors you use. If the motors are lightly loaded (i.e. not trying to drive the car too fast, mechanisms with no unnecessary friction, etc.), then you should be fine with one battery box (if you're using a V1 receiver that will impose a lower limit). On the other hand, I have no idea of the current draw of the servo motor, so you may find that you need two battery boxes. Owen. Quote
Jim Posted January 21, 2015 Author Posted January 21, 2015 The answer is, as is so often the case, "it depends". Your limitation is on current draw, which depends far more strongly on motor load than which motors you use. If the motors are lightly loaded (i.e. not trying to drive the car too fast, mechanisms with no unnecessary friction, etc.), then you should be fine with one battery box (if you're using a V1 receiver that will impose a lower limit). On the other hand, I have no idea of the current draw of the servo motor, so you may find that you need two battery boxes. That makes sense. Since it's a pretty heavy car, I reckon there will be quite some load. So using V2 receivers would be better in this case? Just like Bruno's Ferrari. What's the best setup for two battery boxes? Driving motors on a single battery and all the other functions on the second battery? Quote
Milan Posted January 21, 2015 Posted January 21, 2015 For that one battery box will be more than enough, trust me! And you can connect two Ls on a single output of Receiver. Philo's page is indeed the best source for information available. Quote
Jim Posted January 21, 2015 Author Posted January 21, 2015 For that one battery box will be more than enough, trust me! And you can connect two Ls on a single output of Receiver. Philo's page is indeed the best source for information available. This sounds promising! I will start testing with this setup. Thanks Quote
Milan Posted January 21, 2015 Posted January 21, 2015 V2 Receiver is certainly better at providing more freedom regarding thermal shutdowns, but your best bet is to try. I guess your model will be driver exclusively on flat and hard surface, so V1 receivers protection wont kick in. Quote
Jim Posted January 21, 2015 Author Posted January 21, 2015 V2 Receiver is certainly better at providing more freedom regarding thermal shutdowns, but your best bet is to try. I guess your model will be driver exclusively on flat and hard surface, so V1 receivers protection wont kick in. True, indoor use only! I will do some testing with different setups. I haven't got much experience with these kind of PF setups, so it's good to learn a thing or two. Quote
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