vuurbeving

Regarding the cracking: I don't have any liftarms with cracks after inserting the BBs and axles. The only 2 that cracked happened when I wanted to remove the axle again, and pulling the (excellent BrickTracks) wheels off requires quite a bit of force. That's when the cracks appeared. Also, the cracks are in the exact same spot, at the very tip of the liftarm, right where the plastic is thinnest, I tried to take a photo of the liftarms with the cracks, but that proved to be difficult. Here's a quick picture that shows where the cracks are: I'd say that during normal circumstances, cracks won't happen and are not an issue.

I gave this another try, and I agree with most of your findings. I previously put some BBs in technic bricks (1x2 with 2 holes) and most of the times I found that it was really hard to line up the BBs, since the bricks could move quite a bit. Putting plates on the bottom side helps, but that results in problems on switches, so no option. I had reinforced them with liftarms actually, but never actually put the BBs in the beams itself. I tried different methods to get the BBs in: drilling, heating the bricks then push in and simply pushing in without heating and using a hammer.. Now using your notes, things I observed: - Drilling by hand is not fun :). I ended up using a machine anyway and simply drilling from both sides instead of all the way through. No noticable difference in terms of force required to insert the BBs (can be done by hand). A good quality drill is required (it needs to be 5,0mm) - Simply putting the BBs in does not crack the liftarms. Except when I tried to remove the axle and wheels that were on the end of the liftarms. It required some force to get the wheel off, and that made both the liftarms crack :|. So even though it all fits nicely, I assume the liftarms are more prone to cracking, use a bit of care. - The long (in this case) liftarms do make for a very easy way to make a near-solid structure, so once you line up the BBs correctly, it will stay that way. I'm thinking of trying some longer technic bricks instead, to avoid any possibility for cracks (if there's a crack, the BBs can move more easily and mess up alignment with the BB on the other side) Some other notes regarding BBs: - I have the MR52ZZ, but I plan to order some BBs without shielding. The bearings I have don't seem very well lubricated, and the thinnest lubricant I could find, well, i'm totally not sure it actually got into the BBs. I'm not sure how much dust will affect them, but i'm not impressed with the quality of the current bearings I have at all. - I used bricktracks axles and wheels. No hammer necessary. - Ball bearings are only significantly better running than lego wheel assemblies if you put weight on the wheels. Best reason to use them vs lego wheels is if you run long trains or heavy (8-wide?) trains. I do find it makes a big difference on my 7-wide rolling stock (see picture below). If you only want to make your wheels prettier, you should really consider if it's worth the hassle. - Instead of the 1x4 bricks with studs on the side, I used some 1x2 technic bricks with 2 holes and technic pins, leaving the innermost open. this allows to put technic half pins in the liftarm on the outside to attach some detailing. I found that it did not compromise the strength of the complete structure: - To aid in inserting the BBs, I put a nail in a piece of wood, and cut the top off. I put the BB on the pin, then insert the BB in the liftarm by pushing the liftarm down on top of the BB: So, I simply copied your design more or less and tested the complete assembly on one of my rolling stock and it seems to work great: Thanks for the write-up! It inspired me to try once more after my previous, more or less failed, attempts to convert my stock to BBs based wheels.