JMChristopher Posted January 20, 2014 Posted January 20, 2014 (edited) I have been working on this on and off for nearly a year now and it is beginning to take shape (Please forgive the terrible cell phone pics): I will post some work in progress shots later but for now here is where it is at. It features: 10 wheel drive. 10 wheel steering. fully independent suspension with a little over 1.25" of travel. Maximum ground clearance of 2.375" 3 speed transmission. A compact chassis with motors integrated to add rigidity. Everything is powered by 6 xl motors for locomotion and 4 l motors for functions like steering, gear changes, pnuematic pump, etc. All power functions are controlled by remote. Once complete it will have: Pneumatic stabilizers. Some kind of crane. Here is a pic of one so you don't ave to google it: I would love to hear what you think. Edited January 21, 2014 by JMChristopher Quote
Doc_Brown Posted January 20, 2014 Posted January 20, 2014 Looking good! Can you please show some more detail pics of the suspension and steering? How do you sync up the steering? I was thinking of doing something like this for my next big project. hehe Quote
TinkerBrick Posted January 20, 2014 Posted January 20, 2014 Interesting. Do you have a small video of the trucks performance? Do you plan on making a trailer after the truck is finished? By the size of the truck it must be 1.5 - 2.0m long. Looking forward to see it finished. Quote
JMChristopher Posted January 20, 2014 Author Posted January 20, 2014 Thanks guys. I forgot to mention one other feature. The chassis is modular and is made of 11 sections right now. Each axle is a module, each xl motor pair is a module, the frame and fender above them is a large rigid module. It still takes some work to get everything apart, but there are some "bolts" that can be easily removed to make dis-assembly easy. It may seem like an odd feature to have, but things that work in LDD don't always work in real life, so removing sections and reworking them is a big part of making this thing. To answer a few questions, the steering is the traditional rack and pinion system. The rear section has the tie rods behind the axle and the front section has them in front of each axle. A single axle runs straight through the entire vehicle. This makes it so that front and rear wheels turn opposite directions without the need for any gearing. A single L motor will power this and the linkage between this motor and the primary steering axle is located in the center of the vehicle to reduce the amount of axle flex between front and rear. The only problem is that the steering geometry is not optimal. I do not have a video of this thing in action yet. I need to order 3 more battery packs and 6 more receivers to even get this thing moving. I planed most of this out with LDD and am currently testing how well some of these ideas work in real life. For example the transmission would work well in theory since it is the strongest and simplest design I could come up with and integrate with everything else, but It might still be too weak to hold against the torque of 6 xl motors running through 1 axle. I will have to test this and maybe come up with something else if this doesn't work. I do not plan on making a trailer yet, in fact I don't quite know what I am going to even put on the rear bed. The size is actually less than a meter right now, I am trying to make the wheel base as short as possible since the turning radius is pretty horrible right now. Yes, the remote survived. ;P I would be happy to answer any more questions, post more pics and show any more engineering breakdowns of things. Just let me know what you want to see. I would also appreciate any thoughts or advice you might have as this has become quite the undertaking. Thanks! Quote
Lakop Posted January 20, 2014 Posted January 20, 2014 Nice. I Look forward to more images. What colour will you do the body work in? H Quote
JMChristopher Posted January 20, 2014 Author Posted January 20, 2014 I will finish it out in Yellow. I was going to do a yellow cabin and engine compartment with yellow fenders front and rear. Quote
AndyCW Posted January 20, 2014 Posted January 20, 2014 I drove one of those when I was in the Army. It was harder than I thought. Good thing I just needed to drive it across the motor pool. (parking lot) v/r Andy Quote
andythenorth Posted January 20, 2014 Posted January 20, 2014 (edited) I found that 2 XL motors ganged together will chew gears easily. This might not be a problem if the modular design makes it easy to replace gears. I have an 8x8 truck using the same tyres, roughly same scale truck. The first version had 2 XL with a a diff between them to get variable speeds (each motor on a separate channel, run one or both, the diff equalises). That chewed up the gears in the diff.... The second version had a 2 speed transmission, single XL driving rear wheels, no power to front wheels It had reasonable torque, but not much speed, and chewed up a lot of gears in the transmission Third version has one XL per rear axle, with minimal gear train. One XL drives both front axles, again minimal gear train. It's got reasonable torque, it will pull my 13Kg child on a scooter, and it will push a small table around on a smooth floor. If I ballasted it, it would pull more (loses traction). Yours looks fun. Edited January 20, 2014 by andythenorth Quote
JMChristopher Posted January 20, 2014 Author Posted January 20, 2014 I found that 2 XL motors ganged together will chew gears easily. This might not be a problem if the modular design makes it easy to replace gears. I have an 8x8 truck using the same tyres, roughly same scale truck. The first version had 2 XL with a a diff between them to get variable speeds (each motor on a separate channel, run one or both, the diff equalises). That chewed up the gears in the diff.... The second version had a 2 speed transmission, single XL driving rear wheels, no power to front wheels It had reasonable torque, but not much speed, and chewed up a lot of gears in the transmission Third version has one XL per rear axle, with minimal gear train. One XL drives both front axles, again minimal gear train. It's got reasonable torque, it will pull my 13Kg child on a scooter, and it will push a small table around on a smooth floor. If I ballasted it, it would pull more (loses traction). Yours looks fun. Thanks for the info. I might have to use several sets of gears so there is more than a 1 on 1 meshing, perhaps 4 gears meshed with 4 more gears to transfer power will be enough to handle 6 motors. Quote
AndyCW Posted January 20, 2014 Posted January 20, 2014 The bracing around the gears matters. Try to establish double shear connections. Especially on pinion gears. I have not had any trouble with XL motors eating well braced gears. If it ate a gear, I just added more bracing around the enclosure. v/r Andy Quote
JMChristopher Posted January 20, 2014 Author Posted January 20, 2014 This is what I have to connect 2 xl motors to an axle. This is then set up in series between each axle on the rear portion of the vehicle. I know it is a bit of a strange way to do it (using chains and all) but it is the only way I could bypass the steering axle running directly between the motors. Sorry for it being huge and crappy, this is why I have been holding off posting more pics. Quote
AndyCW Posted January 20, 2014 Posted January 20, 2014 The chains are weak. They will break. There is a reason that they are not used in trial trucks. I wouldn't expect this setup to withhold any abuse, but I don't have a better solution for you. I let my 5 year old son drive my stuff around to find weak points in the design. v/r Andy Quote
JMChristopher Posted January 20, 2014 Author Posted January 20, 2014 Haha, if only I had kids to do that for me. I will have to run some test to see how well this works, but I will have to do a major redesign it sounds like. Quote
AndyCW Posted January 20, 2014 Posted January 20, 2014 I'm just one guy and I could be wrong. Do some tests and let us know how they turn out. Every time I am wrong I learn something new after all. v/r Andy Quote
andythenorth Posted January 20, 2014 Posted January 20, 2014 (edited) FWIW, here's the rear axle unit of v3 of my truck. Both axles are composed into this unit, which can be dropped out of the chassis. Connection to the chassis is as a walking beam. Minimal gear train, and everything comes apart easily if gears split (or axles shear, which has also happened). Hub reduction. Pneumatic difflocks, inspired by Sariel's design. This is v2, which failed. Lots of friction in the drive chain, and single XL up in the chassis. When I disassembled it, I found that it had sheared axles for the gears in the middle of the photo. This was due to torque loads trying to push the gear out of the drive chain, possibly made worse because of flex due to the use of the axle joiner parts. Edited January 20, 2014 by andythenorth Quote
JMChristopher Posted January 20, 2014 Author Posted January 20, 2014 (edited) Interesting... And thanks for all the info. Edited January 20, 2014 by JMChristopher Quote
dhc6twinotter Posted January 20, 2014 Posted January 20, 2014 Looking good! If you have the space, a couple more 16t gears and three 24t gears can work for your configuration. Or, you could use a couple 12t gears, a couple of 20t gears, and three 24t gears if you want a bit more gear reduction. Quote
JMChristopher Posted January 21, 2014 Author Posted January 21, 2014 Ok, here are some more images: Dual xl motor assembly: Axle and suspension assembly: Motor and suspension assembly: The rear assembled: This weekend I will see if I can get all this to work, it probably isn't strong enough and if not, back to the drawing board. :) Thanks for all the support. :) Quote
Technyk32231 Posted January 21, 2014 Posted January 21, 2014 The chains are weak. They will break. There is a reason that they are not used in trial trucks. I wouldn't expect this setup to withhold any abuse, but I don't have a better solution for you. I let my 5 year old son drive my stuff around to find weak points in the design. v/r Andy Double or even triple chains work well though. Quote
JMChristopher Posted January 21, 2014 Author Posted January 21, 2014 Double or even triple chains work well though. The solution is more chains, more gears and more POWAHHHHH!!!! Quote
AndyCW Posted January 21, 2014 Posted January 21, 2014 I think we may have more bad news. spider gears in your differential will not survive u-joint in the knuckles won't either Most trial trucks use hub reduction to reduce the stress on the spider gear and on u-joints. The differential you are using is prone to skipping teeth on the pinion unless some reinforcement is done or there is the aforementioned hub reduction. I look forward to test videos and welcome to the community. I hope you prove me wrong. v/r Andy Quote
JMChristopher Posted January 21, 2014 Author Posted January 21, 2014 I think we may have more bad news. spider gears in your differential will not survive u-joint in the knuckles won't either Most trial trucks use hub reduction to reduce the stress on the spider gear and on u-joints. The differential you are using is prone to skipping teeth on the pinion unless some reinforcement is done or there is the aforementioned hub reduction. I look forward to test videos and welcome to the community. I hope you prove me wrong. v/r Andy I hope so too. I wish Lego parts weren't made out of cake. I wonder if 3d printed parts would be any stronger. Anyway, thanks again. :) Quote
andythenorth Posted January 21, 2014 Posted January 21, 2014 The steered axles are cool, nice use of the torque tube Quote
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