Opinions please

[colmoore]

Hi all,

I'm designing a fairground ride in LDD that is complete, barring a few minor modifications as the ride has evolved. I have stumbled upon an issue that I would like LEGO expert builders opinions on.

The ride is based on two contra-rotating turntables attached (one above the other) to the sides of a trestle and turned by a single crown gear.

I have created a mount to hold the turntables equidistant from the crown gear axle. I have used 7M half beams as spacers to enable the mount to fit into a trestle an even number of studs wide.

My issue is with attaching the mount to the trestle. If I use normal cross axles there is too much "play" and any weight placed on the turntables causes the pieces of the mount to part. I have solved this by using black 3M connector pegs. The problem is because a half beam has been used half of the connector protrudes from the outside of the trestle, as in the pictures shown.

LDD will not permit me to create this joint but I have actually assembled it for real and it works perfectly. The pegs cannot come out and nothing has been forced to achieve this result.

I want to know what people think. Is this an illegal fitting or a limitation of LDD that I should ignore?

Thanks all,

Colin

Trestle by colmoore, on Flickr

IMG_2070 by colmoore, on Flickr

IMG_2071 by colmoore, on Flickr

IMG_2072 by colmoore, on Flickr

Edited April 29, 2014 by colmoore

[AndyC]

The black pegs will be in a permanent state of compression which will damage them over time. Theoretically it could also damage the brick, although I suspect the pegs would give way before any real wear on the brick. So it's not a strictly legal design, but I can't think of a better solution and, let's face it, technic pegs aren't exactly in short supply, so I probably wouldn't worry about it.

[Gnac]

AndyC explained perfectly why LDD doesn't allow this, but there is a viable option both in LDD and for your assembly:

3/4 pins, whose sole purpose appears to be in allowing connections between half-beams and full-width holey-things. These should stop any unwanted lateral movement, but not weight induced sag (and eventual damage), so it would be best practice to have a couple of bricks below the beams to take the load off them.

[colmoore]

Thanks so much for your feedback guys.

I have investigated 3/4 pins and whilst they do solve the problem with regard to the length of pin they unfortunately don't have friction ridges, which is key to making the whole fit tighter and stronger.

I have decided to remove the spacers altogether and modify the trestle using jumper bricks to shift the turntables the required 1/2 stud.

Once again thanks for your guidance.