LEGO Technic Power Functions remote control drivetrain for heavy vehicles. 4 XL motors, 1 Medium motor, 2 Battery Boxes and 2 IR Receivers.
About this creation
I've had a few requests asking to see some more details on the Power Functions remote control drivetrain in my Fiat 682 Race Transporter, so here are a few bonus pictures and a (very) short video. There are builders on MOCpages who are loads better at Power Functions than me, so make sure you have a look at their MOCs too so you get the best information available.
Components:
- Drive: 4x XL motors
- Steering: 1x Medium motor with clutch
- Power: 2x 9V Battery Packs
- Control: 1x IR Transmitter, 2x IR Receivers
Cargo Area: This has enough room for all the Power Functions components. Here you can see three of the four XL motors driving the vehicle, and the two battery packs. The fourth XL motor is directly underneath the three you can see in this photo (so they make a 'T' formation). Each battery pack powers two XL motors and an IR receiver (mounted in the ramps of the truck). One of these battery packs also powers the Medium motor used for steering.
The Battery Packs' switches are connected together by the black Technic lift-arm thingumy you see arching over them. This makes it much easier to switch them both on/off as it forms a nice big handle that's easily reachable when you remove the roof.
Chassis: From left to right you can see; the differential, gearing down for drive, drive motors, steering motor and clutch, gearing down for steering.
XL motors are extremely powerful (we'll come on to just how powerful in a bit). As such the chassis needs to be very tough. The Fiat's uses four Technic beams, joined by cross members every few studs and plated to at least 2 thick both above and below. In addition, it also uses two smooth Technic lift arms to clamp the chassis together at the area under most pressure. This took a lot of trial and error; every time the chassis cracked I fixed that area - tested it, found the next area of weakness and so on.
Damage! Once the chassis was indestructible the next failure point were the LEGO cogs and axels. This is what happens when you miscalculate the torque being put through them (I also busted about 6 cogs).
This occurred when I went from two XL motors to four. Two XLs needed to be geared down twice (meaning a slower but more torquey model) to take the weight of the truck (4.5Kgs). With another two XL motors added I didn't need to gear the truck down so much, and the torque was so high it was twisting bricks! As such the truck is now only geared down once (as you can see in the second picture), and the gears are doubled and connected by both the axel running through them, and Technic pins, to take as much pressure off them as possible.
The truck is now reasonably quick and pretty reliable too, but it's taken a while to get there, so don't worry if your first heavy duty Power Functions drivetrain requires some tweaking!
Video:
I hope this helps answer some of the questions being asked about the Fiat. If you need to ask anything further please feel free in the comments section below. Apologies a few bits in the first picture are wonky - the truck was looking a bit tired that day after much fiddling/turning upside-down etc!
Quoting LK , the Scientist
nice! the info about the electric motors war really helpfull! i own the lego technic rc bulldozer, and a powerfunctions jeep, and want to combine them together to build a scale model of a bmw. i have: 2 remotes, 2 IR receivers, 2 XL motors, 3 "normal" motors, 2 battery packs and light elements. will it be enough? the car will be about as big as the 8435 blue jeep. will it be enough? i want to include RC driving, light, opening doors, boot and bonnet, fully independent suspension, front wheel drive and brakes... but it won't look as good as the fiat you built! amazing job, huge amounts of lego used!
nice! the info about the electric motors war really helpfull! i own the lego technic rc bulldozer, and a powerfunctions jeep, and want to combine them together to build a scale model of a bmw. i have: 2 remotes, 2 IR receivers, 2 XL motors, 3 "normal" motors, 2 battery packs and light elements. will it be enough? the car will be about as big as the 8435 blue jeep. will it be enough? i want to include RC driving, light, opening doors, boot and bonnet, fully independent suspension, front wheel drive and brakes... but it won't look as good as the fiat you built! amazing job, huge amounts of lego used!
Incredible, it must be quite powerfull, that twisted axle is just wow, I thought it would rather break instead of getting so deformed. I think I'll keep it at light swift RC vehicles, much easier :P
Quoting ~~ >=) Christian J (=< ~~ '
Okay, I forgive you. now, Anyway, for my comment on this MOC... It's impressive! Your cars are one of the best I've seen! ( I'm being honest)
That's very decent of you : ) Your MOCs are coming along nicely too. I hope the mods see this - I think they'd be proud of you : )
Impressive! It's a great build, and the power functions are really excellent. I can't imagine how cool it would be to see something like that driving around, great work!
Cool, these are great Power Functions for this beauty! It must have been tricky to get the torque/speed relation right. The photo of the distorted Technic axle is very impressive! Great job! :-))
This thing is huge! And it looks just like the actual truck. I'm impressed at the "built" lettering on the side, and the drivetrain seems to work nicely. Makes me wish I had some power functions stuff!
Quoting MortalSwordsman .
Hi Ape. Its great to see this beautiful moc in closer detail. It is a lot faster than I expected.
Quoting Joost Cumps
Wow Ape, I am really impressed with the speed, that is really quick man!
Yeh, now it's only geared down once it has some reasonable speed. That's the power of four! (I need a sticker saying that like Virgin have on their 747s!) The gears on the engines are now doubled too (they're not in the picture here).
Hi Ape. Its great to see this beautiful moc in closer detail. It is a lot faster than I expected. I was hoping it was going to crash into the camera :). I can't believe the twisted axle. I have a few twisted ones myself but none quite that bad!
I've got to get me some of those... all my electrics are little 4.5V and 9V motors from the '80s - there's no way they'd move the transporter! I'm impressed.
I notice a couple 8-tooth gears in there. Be careful using those with such a high amount of power. I realize you have two in there, but those gears are quite prone to breaking under high torque.
Quoting AntAnt .
Brilliant drive train. I guess the truck crashed into the camera at the end, like my video: http://www.youtube.com/watch?v=IY5y-srsnQk
Its always annoying when that happens
Brilliant drive train. I guess the truck crashed into the camera at the end, like my video: http://www.youtube.com/watch?v=IY5y-srsnQk
Its always annoying when that happens
Wow, Ape! Man, that must have had some SERIOUS torque to twist that axle! The more I get to know about RC Lego, the more I get scared! :( (trembling.....)
