Tobaganner

Tatra 815 8x8 help!

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So I would like to build a tatra 8x8 scaled with the 94.8 x 44 R Balloon tire. I would like to put in 3rd party r/c elements. I would like to put in 1 lipo for 2 motors for the left side of the wheels and 1 servo for the front t4 tires, another lipo with the same for the right side and a servo for the back 4 tires. I would also use another lipo for the lights, winch, and two stepper motors with 90 degree rotations each for the transmission. it would be helpful to know if it would just be better to use 1 motor for each side and what elements I should buy, also I would like a remote control with two vertical sticks controlling the drivetrain and two horizontal sticks for steering, I would prefer to have a physical remote but if there is a r/c IOS app with a antenna I could buy that would also be good. Thanks in advance

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50 minutes ago, Tobaganner said:

I would prefer to have a physical remote but if there is a r/c IOS app with a antenna I could buy that would also be good. Thanks in advance

 If you use lego elements instead, you could use a sbrick, and use lego motors. They use ios.

https://www.sbrick.com

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1 hour ago, Tobaganner said:

So I would like to build a tatra 8x8 scaled with the 94.8 x 44 R Balloon tire. I would like to put in 3rd party r/c elements. I would like to put in 1 lipo for 2 motors for the left side of the wheels and 1 servo for the front t4 tires, another lipo with the same for the right side and a servo for the back 4 tires. I would also use another lipo for the lights, winch, and two stepper motors with 90 degree rotations each for the transmission. it would be helpful to know if it would just be better to use 1 motor for each side and what elements I should buy, also I would like a remote control with two vertical sticks controlling the drivetrain and two horizontal sticks for steering, I would prefer to have a physical remote but if there is a r/c IOS app with a antenna I could buy that would also be good. Thanks in advance

What scale would you be planning on building in? If you using one motor for each side of the vehicle so you can tank steer along with regular steering I would recommend two brushed 380 can-sized motors for 1/10 but anything larger would stress them without a very large gear reduction, 540-550 can-size motors would work for 1/8 well but would be hard to deliver that torque through Lego parts. If you want 1 motor for both sides 1/10 a 540-550 motor would be fine, for 1/8 a 540-550 would be fine also you would just have to get a higher-turn motor gain more torque but loose speed. I think a Nimh battery would work fine, easier to use and does not take an expensive charger, 6-cell would work fine, for lights a small 1 cell LiPo would be fine. For your controller, I think an airplane-type controller would most likely work fine but I just use the standard 3-channel car transmitter. I think you would need about 6 channels, drive-steering-rear steering-lights-transmission-transmission, but if you wanted a winch and different controlled sides of the drive chain that would be 2 other channels which would cost a lot. If you wanted different controlled drive-chains to tank steer that would require two ESC's which would be a higher cost and would require a much better radio, one that you can program. I would recommend only a two-speed transmission, three speeds would be a little overkill.

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1 hour ago, Aventador2004 said:

 If you use lego elements instead, you could use a sbrick, and use lego motors. They use ios.

https://www.sbrick.com

I will not use them because the brick is way too expensive and Lego elements aren't powerful enough for this type of project

47 minutes ago, JJ2 said:

What scale would you be planning on building in? If you using one motor for each side of the vehicle so you can tank steer along with regular steering I would recommend two brushed 380 can-sized motors for 1/10 but anything larger would stress them without a very large gear reduction, 540-550 can-size motors would work for 1/8 well but would be hard to deliver that torque through Lego parts. If you want 1 motor for both sides 1/10 a 540-550 motor would be fine, for 1/8 a 540-550 would be fine also you would just have to get a higher-turn motor gain more torque but loose speed. I think a Nimh battery would work fine, easier to use and does not take an expensive charger, 6-cell would work fine, for lights a small 1 cell LiPo would be fine. For your controller, I think an airplane-type controller would most likely work fine but I just use the standard 3-channel car transmitter. I think you would need about 6 channels, drive-steering-rear steering-lights-transmission-transmission, but if you wanted a winch and different controlled sides of the drive chain that would be 2 other channels which would cost a lot. If you wanted different controlled drive-chains to tank steer that would require two ESC's which would be a higher cost and would require a much better radio, one that you can program. I would recommend only a two-speed transmission, three speeds would be a little overkill.

I was thinking about having a switch on the car for lights, and the reason why I want two drive trains is to eliminate slip situations and have skid steering(one would control the four left wheels while the other would control the four right wheels), Also the reason why I want two servos is because I want regular steering, and crab steering. I could also live with having a switch on the vehicle for the winch. I was thinking about having a 3 or 4 speed transmission, could you explain why it would be overkill? Also I was thinking that one of the drive trains and a servo would be one battery, the other drivetrain and other servo would be powered by the second battery, and a third battery would have on board switches for the winch and lights while controlling the transmissions (one for each drivetrain). I want to roughly scale the model using the wheels for scaling, so using the wheels that I specified in the original post you can scale it, although I am not trying to get a 1/8 or 1/10 scale, just something large enough to house all of the functions. Legos breaking isn't a concern of mine since people sell metal Lego pieces and I am planning on using ball bearings to increase efficiency.

Edited by Tobaganner

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2 hours ago, Tobaganner said:

I will not use them because the brick is way too expensive and Lego elements aren't powerful enough for this type of project

I was thinking about having a switch on the car for lights, and the reason why I want two drive trains is to eliminate slip situations and have skid steering(one would control the four left wheels while the other would control the four right wheels), Also the reason why I want two servos is because I want regular steering, and crab steering. I could also live with having a switch on the vehicle for the winch. I was thinking about having a 3 or 4 speed transmission, could you explain why it would be overkill? Also I was thinking that one of the drive trains and a servo would be one battery, the other drivetrain and other servo would be powered by the second battery, and a third battery would have on board switches for the winch and lights while controlling the transmissions (one for each drivetrain). I want to roughly scale the model using the wheels for scaling, so using the wheels that I specified in the original post you can scale it, although I am not trying to get a 1/8 or 1/10 scale, just something large enough to house all of the functions. Legos breaking isn't a concern of mine since people sell metal Lego pieces and I am planning on using ball bearings to increase efficiency.

Okay thanks for clarifying on the drive-chain, since you're using two different drive axles and metal parts, two 540 can-sized motors would work well, you would have enough space with the 8x8 size. I think the 3-4 speed transmission would be overkill because when you get more and more speeds the amount of gears skyrockets and you gain lots of friction with typical Lego transmission driving rings with all the unused gears. I would recommend an un-sequenced transmission inspired by Sariels Heave Duty Linear Transmission but using 3:1 gear ratios and 1:1, the Traxxas Summit, a very good crawler uses a 25:1 and a 75:1 gearbox, mostly the same concept but it uses a more transmission-driving-ring inspired design. Last thing about the transmission, those 550 can motors if you get a high turn version can be VERY torque-y and if you are using two of them you should be fine with only 2 speeds. I would recommend a 35t motor or something around there, they are a good mix of torque and speed.

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1 hour ago, JJ2 said:

Okay thanks for clarifying on the drive-chain, since you're using two different drive axles and metal parts, two 540 can-sized motors would work well, you would have enough space with the 8x8 size. I think the 3-4 speed transmission would be overkill because when you get more and more speeds the amount of gears skyrockets and you gain lots of friction with typical Lego transmission driving rings with all the unused gears. I would recommend an un-sequenced transmission inspired by Sariels Heave Duty Linear Transmission but using 3:1 gear ratios and 1:1, the Traxxas Summit, a very good crawler uses a 25:1 and a 75:1 gearbox, mostly the same concept but it uses a more transmission-driving-ring inspired design. Last thing about the transmission, those 550 can motors if you get a high turn version can be VERY torque-y and if you are using two of them you should be fine with only 2 speeds. I would recommend a 35t motor or something around there, they are a good mix of torque and speed.

Thanks a lot!

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So I am thinking that I will connect the steering, driving, and gear changing to one channel, will it mess the receivers up if there are three on one channel?

Also, are there receivers that have 3 motor outputs?

 

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@Tobaganner it is nice that you are decided to make tatra, but I suggest to take photos of some prototypes and uploades them here maybe we could help you in better way when we see images

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17 minutes ago, Tobaganner said:

So I am thinking that I will connect the steering, driving, and gear changing to one channel, will it mess the receivers up if there are three on one channel?

Also, are there receivers that have 3 motor outputs?

 

You can't put all three on 1 output, I use a typical 3 channel car remote, the FlySky FS-GT3B, on the receiver there are 3 ports + a battery port (you would need a different remote with more channels, more on that later) to have two motors that you can control direction independently of each other you will have to buy two ESC's, I would recommend the HobbyWing 1060 brushed ESC, it's relatively cheap and works well. You would need to buy a servo-wire splice with one female end and two male ends, so you can plug the female side into the receiver motor port and the two male side into the ESC. To get independent motor control you would need a switch that would reverse the polarity of the wires coming out of the ESC, switching the negative and positive, that would be actuated by a servo. Doing that would reverse one motor so you can tank steer, keep in mind after doing that pulling the throttle stick would make it turn in place, lets say the previous forward would be turn left, and the previous reverse would be turn right. For the steering you need two ports, one for the front steering, one for the rear like you want. The total receiver you need for the cheapest option are, 1 for drive, 1 for drive-motor reverse, 1 for rear-steer, and 1 for front-steer, so a total of 4, lights and winch would have to be manual. I would recommend signing up to a hobby RC web-sight, I'll PM you the link to avoid posting here, the people there are a lot smarter with this them me and might have a much better idea.

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