148 CAD clarification

I have been studying 148 different CAD release from throughout the years and there is this part the at they use in most of their resent robots which I just can’t understand its function

it’s like a bearing block but it’s not moveable for chain tensioning

I just don’t understand what its purpose and hope a wrangler or someone with better understatement them me could clarify


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Just a bearing holder they add to stiffen up the bearing mounting area to handle the point loads around the bearing, no need for a tension mechanism if the exact proper center to center distance is used, which I am sure they are careful to do.


Chains stretch after prolonged use, necessitating a tensioning system of some kind. If you’re doing something like this, you have to pre-stretch your chain (which I’m assuming 148 does).

I have been corrected.

This isn’t necessarily true. We ran direct C-C on #25 chain this year by simply adding 0.018" to the chain run. Even with fairly poor machining, we ran fine all season with it.
Small note as well: chain mostly wears, not stretches. The bushings and pins widen up and let the chain links drift apart a little.


This is good information, thanks!

Maybe we can drop some weight next year by omitting our usual Vex bearing blocks.

Fake news.

We’ve run without tensioners (and mostly no issues) the last few years.

Poofs and some others have as well.


Could you elaborate on the “mostly” part?

We do something similar. It’s most likely just for reinforcement of the bearing. If they are using .09" aluminum, that may be a little thinner than they like to support their drivetrain. By doubling it up in that spot, the bearing is supported a lot more.

The other advantage to this is that if you make the bearing hole in the main drivetrain structure a bit bigger you can account for slight changes by remachining that single piece instead of an entire rail. Not sure if this is being done here and you probably want thicker bearing blocks to make it work but it’s what we’ve done with a WCD and similar bearing blocks.

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