Cement Truck

[dolittle]

Hi,

Has anyone built one? does anyone have the instructions for one?

I m mainly worried on how to do the rotating back part drum:

[CP5670]

Dennis Bosman has built some great cement trucks in the past. They're on his website.

[Milan]

Just search Mixer in BS.

Here are the best results, aside from Bosman ofc:

http://www.brickshelf.com/cgi-bin/gallery.cgi?f=391918

http://www.brickshelf.com/cgi-bin/gallery.cgi?f=409802

http://www.brickshelf.com/cgi-bin/gallery.cgi?f=425043

Mixer (drum) is extremely hard to make, according to Bosman's experience. Read about it on his site.

[allanp]

Just quickly designed this to give you some ideas, hope it helps.

Edited August 22, 2010 by allanp

[dolittle]

Thanks everyone for the answers...

My main concern was the drum, which I was given a few ideas on how to do...

I think I will go with Technic version (allanp) rather than the Classic version of the other models.

Thanks,

Noam

[allanp]

Thanks everyone for the answers...

My main concern was the drum, which I was given a few ideas on how to do...

I think I will go with Technic version (allanp) rather than the Classic version of the other models.

Thanks,

Noam

Sweet! I'de love to see it when it's finished!

[dhc6twinotter]

Well awesome! I'll be watching this thread. I've often thought a Technic cement truck would be a fun build. Looking forward to your build. Any idea on what truck this will based on?

[Frequency]

Those look really good I was thinking about this a while ago and contemplating making one

what i did consider was using a technic turntable at the cab end of the drum and driving that with the motor and possibly having one at the the other end too as the opening that way you can get around the problem of the stress the drum would create on just supporting it with an axle through the middle except maybe the angle might create too much friction in the turntable part i don't know.

[dolittle]

Those look really good I was thinking about this a while ago and contemplating making one

what i did consider was using a technic turntable at the cab end of the drum and driving that with the motor and possibly having one at the the other end too as the opening that way you can get around the problem of the stress the drum would create on just supporting it with an axle through the middle except maybe the angle might create too much friction in the turntable part i don't know.

Assuming you are planning on putting the drum at 30^o angle - I believe this is the one of real drums - I don't think a turn table will suit here.

I was thinking of putting what is usually done in Lego designs when an angle of non 90^o is required - like for wheels - two bricks connected with a cross brick at the angle required

This will hold the "main shaft" which the drum ends will connect to and rotate on

Since the main beam/connector is a "wheel" with a cross in the middle - it will hold it in place and rotate when force/rotational force, is applied to it

Hope to show something more in the near future - I need to get a hold of the needed parts first

[allanp]

The drum should be lightweight and rigid enough to be supported easily by standard axles, the 40 tooth gear at the front could be used to drive it if you were still worried but it should be fine. I did think about putting a turntable at one end to make use of the hole in the middle, would have been a nice touch but i'm not sure if the friction would cause the drum to twist just slightly, making it's rotation jerky. You could also try adding a flex tube running up the middle in a spiral, mimicking the spiral blades in the real thing used to empty the drum when running backwards.

[CP5670]

The drum should be lightweight and rigid enough to be supported easily by standard axles, the 40 tooth gear at the front could be used to drive it if you were still worried but it should be fine. I did think about putting a turntable at one end to make use of the hole in the middle, would have been a nice touch but i'm not sure if the friction would cause the drum to twist just slightly, making it's rotation jerky. You could also try adding a flex tube running up the middle in a spiral, mimicking the spiral blades in the real thing used to empty the drum when running backwards.

This would be a good feature. The minifig-scale 7990 actually does this, but uses specialized parts for the drum that have the spirals inside.

I think turntables are definitely the best way to hold the drum in place. Studded turntables may be a better choice than the studless ones (they seem to have lower friction), or you could use the smaller 4x4 turntables. Standard axles will twist and bend if they are supporting the weight of the whole thing.

[eMHa]

This would be a good feature. The minifig-scale 7990 actually does this, but uses specialized parts for the drum that have the spirals inside.

One of my sons has 7990 and I was amazed by the correctness of the drum. Unfortunately the drum is a two part piece which can't be really used anywhere else. But it's to small for a technic creation I think.