8 replies to this topic

[sama]

Hi guys! I am brand new to mocs and I want to start my first one. I am going to use one 8053 mobile crane set, one 8110 Unimog set, and one 8043 Motorized excavator set. I want to base the design off the following picture:



I have the large Unimog wheels and all the necessary parts (gears, suspension, m motors, receivers  beams, etc.). I just want to ask, are two m motors good enough to power (its going to be 4wd) something similiar to this size (length 32cm by width 26.5cm by height 20cm)? I am going to use another m motor to switch the dual speed gearbox. the gear ratios are probably going to be 1.4:1 and 11.6:1 (fast and slow). Additionally  I will use another m motor to steer the truck.

Is there any way I can get the portal axle hubs to create a double wishbone suspension using beams and stuff? Also, I just need to know if the m motors are enough to power this thing (it won't be too big but it will have a PF 9v battery box on it)?

Will three m motors be enough to drive this thing over large obstacles (on first gear)? Please help.

Edited by sama, 04 November 2012 - 07:38 PM.

[Hopey]

I've got a similar collection, consisting of 8110, 8043 and 8109 (flatbed truck) and have had a couple of goes at building crawlers.

One was an attempt to recrea te the 9398 crawler, which used 4 m-motors for drive and one for steering. This was quite heavy and needed to be geared down a bit to get it to do any decent climbing. One thing I discovered with this was that driving 5 motors at once doesn't work; as soon as I tried to steer the drive motors slowed noticeably.

The other one was trying to do a simple, light chassis, with each wheel independently driven by an m motor. This one was much lighter, and crawled much better. This used a linear actuator to steer so that I wouldn't need to stall the steering motor to steer.

I don't think you'll be happy with the performance of 2 M motors, but 4 works very well if you can keep the weight down (see the video in the second link above).

I'm not sure how well you'll be able to make a suspension system, I have a similar part list and found myself quite limited. You've got a few more of the 6L links than I do, so might be able to do a bit better. You can certainly make a double wishbone suspension with the portal hubs, but I think you'll end up with something that's very wide, and not particularly tight. (I'm planning on getting myself an 8070 for christmas to expand my suspension possibilities).

[sama]

I just need to know how you could make a steerable front hub connected to double wishbone suspension with the portal axle hubs with the pieces provided. I can't seem to figure it out.

[Lipko]

Take a look at the recent civic thread for example.
But Hopey is right, you should get some better suspension pieces. It doesn't have to be the 8070, as far as I remember the orange quad has some wishbone pieces too. They are from the smaller kind, but you have to build long wishbones anyway.

[Saberwing40k]

Well, I've got a wishbone system with portal axles:

However, this may or may not help you, as it requires some uncommon pieces. I'd recommend going on ebay and buying a big honkin' lot of technic parts so that you have more to work with.

Oh, and if you need more pictures, just click here.

[pint14]

I think you should use xl motors or l motors, m motors are a bit weak.

[D3K]

Take a look at my recent build http://www.eurobrick...pic=74386&st=25 .
It has very solid double wishbone steerable setup, but you will need some tow-ball pins (not the cross-axle ones found in numbers in 8053) and some of the 6L steering arms. All the other parts I would think you've got covered with the 8043, 8053 and 8110 together

[Hopey]

D3K, on 05 November 2012 - 09:11 PM, said:

Take a look at my recent build http://www.eurobrick...pic=74386&st=25 .

That uses 8 of these wishbone pieces, which he doesn't have.

Anyway, you got me thinking about it, and I reckon it's possible. Here's my first attempt:





Obviously it's just a concept, and there's a few challenges left as an exercise, such as attaching the other end of the spring to something, doing the steering linkage, and of course driving it, but that shouldn't be too difficult.

Note the offset of the uni joints. Typically the centres of the uni joints would be in between the pivots of the wishbones, but that's not possible in this case, as the outer one needs to be on the steering axis. They don't have to be between the pivots, however, the lengh of the centre part of the linkage just has to be the same length as the wishbones (5L in this case). I hope that makes sense.

My first intuition was to use 4 liftarms per wheel, but this seemed unnecessary, and the two I've used above seem to be enough.

I might make something based on this myself if I can find the time...

[sama]

Oh these are nice! Thanks guys, I would have never thought of these ideas. I am touched.