Play of bearings around the bolt

Hello, I’m a new user from Spain starting a new build.
First of all I want to thank @Vicious1 for the project, and the community for tis great forum, most of my doubts were solved reading around here.
I’ve already printed all the parts and I’m waiting for some components.
I tested the calibration of the printer before printing and it is spot on now, it was just a little bit out of square, good I followed the instructions before printing and noticed it.
i jus tested one of the trucks on the pipe and looks great and moves great according to instructions.
One thing I noticed, there is a lot of play between the bearing and the bolt. the ID of the bearing is indeed 8mm, but an 8mm bolt is about 7.75mm in diameter, so a bit of bad lookin play. I first tried with bolts with thread all the way to the head, and later bought some bolts with thread up to the middle and 30mm of smooth rod to the head , so the bearing and plastic part sit on the flat part and not the thread (I think they are 60mm long, I planned to cut them to length) Unfortunately the smooth part is also 7.76mm, so the play is still there.
So I thought then on installing 8mm carbon fiber tubes with 5mm inner hole, with 5x40mm bolts (and wide washers on the ends to hold the plastic part and bearing) this way I eliminate the play between the bearings and the printed parts, and also I can save about 750grams on the moving parts (measured the m8 bots and nuts to be 1108 grams, and m5 and nuts 288 grams, have to add the carbon pipe and washers, which are very light anyway compared to m8)
so my questions are here:
-is this 0.2mm bearing-bolt play something I should take off my head, and continue living my life? (I expect a “yes” to this question)
-is that 3/4 of Kg something worth eliminating off the moving mass? there should not be a significant cost increase here, the carbon pipes are really cheap due to drone DIy market, and I save a good amount replacing m8 with m5 bolts
ok, that’s it, didn’t find any thread bout this subject, so it was worth asking

1 Like

No don’t worry about either of those.

A little bit of play is okay, there are tensioners built in where needed and the parts themselves are slightly undersized to start with.

Weight is not the biggest of issues at the speeds we operate at. It matters but not enough to make things difficult on yourself.

Maybe one day you can build a second one and see if I am wrong about any of that. I love proof, because my assumptions are not always right.

ok, i will try with standardized procedures if that play doesn’t cause a problem. but maybe sin the future (most probably not if everything works well) I take some measurements to see how much the weight affects the pipes (weight/span vs sag), since the motion is not a problem. I think its worth trying as the m8 bolts are 100g heavier than the router I’m using. anyway these 1.5mm wall pipes are way stronger than one can think.
thanks for the reply, I hope I don’t need to ask anything else, and just post here showing the extremely ugly machine (mix of leftover colors) or some nice piece made with it.

1 Like