My Technic Challenge | Not for the faint hearted

[cgg199]

This challenge is one that I have tried many times, and most certainly failed. Unlike other challenges, this requires huge levels of skill, talent and engineering ability. Which clearly, I don't have. Anyway, onto the problem in hand. I am designing a car, a supercar in fact, with brakes and such like, which I am more than happy with. But then it comes to the gearbox. The hardest bit of all. I can't do it. So. The challenge is, can people design a gearbox for the car to win..... The pride of having your gearbox in my car. So, what I need from it.

5 speed with reverse

To fit (obviously)

To be able to handle the torque of 2 XL motors

To be shifted from gear to gear, using one motor only.

The position of the gearbox is up to whoever designs it but remember. There will be some front overhang as well, but a chassis section for this hasn't been implemented yet. Also, this is just the basis for a chassis. It needs a LOT of reinforcing.

The car will have a functional cockpit (working pedals etc)

A flat 6 or V8 engine will be mounted in the front of the car

I need space for mechanisms and motors.

The simpler the better, and the more compact the better.

Now, off with y'all to see what can be thought of.

If only I knew how to post an LXF file on here...

Edited July 8, 2013 by cgg199

[ciken]

you need to upload the LXF on dropbox or box or an other upload program and then just post the link

[legomuppet9]

Impossible... a gearbox controlled by one motor would not be able to handle that much torque, especially one with tat many gears. trust me I've tried...

Supercar WIP - Gearbox by legomuppet9, on Flickr

[Alasdair Ryan]

A linear gearbox is your best bet,but I agree with the Duplomuppet9 that I don't think the gears would last very long under the tourqe of two XL motors.

[cgg199]

It's been done. Sheepo has done it, so how come his gears don't get stripped?

Edited July 8, 2013 by cgg199

[legomuppet9]

A linear gearbox is your best bet,but I agree with the Duplomuppet9 that I don't think the gears would last very long under the tourqe of two XL motors.

Mr Alasdair, what are you on about?

Sheepo has kind of done it yes, but it's very complex and not very reliable...

[Meatman]

It's been done. Sheepo has done it, so how come his gears don't get stripped?

Maybe not right away, but I would almost guarantee that they would eventually. It is just a matter of time before the driving ring/16 tooth clutch gears give. It's only little pieces of plastic that engage them.

[z3_2drive]

If you're that concerned about it being RC and also having a gearbox a simple two speed or three speed would end up being lighter, maybe stronger reinforcement wise, and it would be functional because it would be able to handle all the torque.

[cgg199]

There must be away, of gearing the XL motors up, to reduce torque, for the purposes of the gearbox. Then, gear them down again. I don't know to what extent, but does anyone think that would work?

[allanp]

There must be away, of gearing the XL motors up, to reduce torque, for the purposes of the gearbox. Then, gear them down again. I don't know to what extent, but does anyone think that would work?

That would reduce the stress on the gearbox but is very wasteful on power. First you have the internal motor inside the xl motor, then you have it's own internal gearing down, then you would add your own gearing up, then you would add a transmission gearbox (the currents parts are very inefficient already), then you would have another stage of gearing down to the wheels. After turning all that you would hardley have any power left at the wheels. Ideally you could use buggy motors. They have less torque than an xl motor but they spin much much faster giving almost twice the power of an xl motor overall whilst putting less strain on the gearbox. Alternatively you could use L motors. Although they don't have the power of an xl motor, by not having so many gears to turn before the transmission you prevent alot of power wastage and so might give you about the same amount of power at the wheels whilst also making it simpler and more compact.

[Bricktrain]

I have used two L motors for my crane so that there is less torque through the gears and then added more reduction at the final drive, might be easier than using XL motors for you.

[Saberwing40k]

Hmm, you could maybe use a planetary transmission for this purpose. I've also built a transmission that works similar to ratcheting boxes, and does not use driving rings. On the other hand, why do you even need the gearbox in the first place? I mean, sure, a 4 speed gearbox would be good, but why 5 with reverse? A reverse gear is just more complication, and for what? You have electric motors, that can be reversed at any time, so unless you're going for realism, there's no reason for it to be in there. XL motors can destroy gears, but not in applications like this. Sheepo's gearboxes should be what you need.

[cgg199]

Thanks for all the help. Yes, realism is what I'm going for. It doesn't need brakes, but it's got them. It doesn't need working pedals, but it'll have them.

My plan for now is to just have a simple manual gearbox, and maybe branch out at some point. Using a 4 speed sequential could be useful too.

Edited July 9, 2013 by cgg199

[legomuppet9]

Thanks for all the help. Yes, realism is what I'm going for. It doesn't need brakes, but it's got them. It doesn't need working pedals, but it'll have them.

My plan for now is to just have a simple manual gearbox, and maybe branch out at some point. Using a 4 speed sequential could be useful too.

Simple manual gearbox would be a lot easier to implement, and would result in an overall better model at the end if you aren't a particularly experienced MOC'er

[piterx]

for my fulvia i had 3+R with clutch and power from two L motors and it worked quite well....but still far from saying that "my gearbox was perfect"

[Someonenamedjon]

How about this one, but you would have to add more gears.

[cgg199]

That's a really nice gearbox Jon and with some modification it could be brilliant. I' am going to stick with a manual though.

[piterx]

the manual is just useless for a simple reason: if the car can start with the 5th gear then there's no reason of adding the weight of the gearbox

[legomuppet9]

I doubt Jon's suggestion would be able to handle much torque...

the manual is just useless for a simple reason: if the car can start with the 5th gear then there's no reason of adding the weight of the gearbox

Realism

Edited July 9, 2013 by legomuppet9

[Lipko]

You have to stop somewhere with realism. If you want true realism, build a real car.

Edited July 9, 2013 by Lipko

[legomuppet9]

I think if you are going to do a manual gearbox, then don't motorise the car...

[cgg199]

I'll fill everyone in on where I am.

I wanted to create a Ford F150, but after many different axle designs, soon gave up. I then decided to build my own super car, which is currently being designed. The idea was to create something amazing, with many different features, most unecesary but there for realism. I'm still trying to find a way around it, but my options are running out.

All along, I wanted something that could be enjoyed with and without PF to the same extent. This would include a working gearstick, working pedals, so when they are pressed, the said action does it's job (obviously not the accelerator). The PF system would be able to be implemented into the car very easily once the model would already be built, so it would be easy to convert it either way.

The annoying thing is, I have each section planned out in my head (except the gearbox but now with the aid of Sheepo's design it should be coming along) but when putting it onto LDD it just isn't coming out quite as I wanted. Each mechanism has such a simple design, but it is really starting to annoy me now, that this gearbox is causing all this hassle.

There's the car really, nothing that has never been done before, but some big ideas all the same.

[Lipko]

We could point out many models which are absolutely awesome and doesn't have tons of features.

The biggest problem with realistic, advanced and/or never-seen-before features is that pretty much only you and some experts-in-the-field (if you point these features out...) will recognise them. My favourite among these advanced features are the suspension geometry features, all those angles. No-one will see them unless you point them out. They are even pointless with Lego that has more backlash than the tiny angles in the suspension.

In my opinion a model is good feature-wise, if those features are clearly recognisable and add some playing value.

[piterx]

here it is...give it a go :) you can easily add two gears more

Edited July 9, 2013 by piterx

[cgg199]

@Lipko - I'm not into the geometry details, and all that, but some features are a must for me.

@Piterx - Cheers mate! I've got some plans (proper ones now) for a hybrid of yours and Sheepo's gearbox. I'm sticking to 3+R so I'll be using your gear setup.

Thanks again everyone!