Loctite vs press fit

[Munchskull]

My team has taken to CNCing out our WCD rails with center to center chain. Because of this we have been milling our bearing holes to 1.124 together a press fit. This causes us some pain in being super exact.

We have also used loctite 648 else where on the robot for bearings with good success starting with a line fit.

What do you use to retain bearings and what has been your experience?

[engunneer]

not compatible with all situations, but we generally do a slip fit and use flanged bearings and shaft collars to constrain the bearing axially. In cases where we can't use this method, we tend to do press fit.

[Cory]

loctite works totally fine. Make sure you get the appropriate one based on the size gap it needs to fill. Also make sure to use the primer on both pieces.

[engunneer]

Originally Posted by Cory

loctite works totally fine. Make sure you get the appropriate one based on the size gap it needs to fill. Also make sure to use the primer on both pieces.

and make sure to get the right kind for removal should you need to take it apart. some will loosen with heat, and some won't. in 2001 we accidentally assembled our shifting gearboxes with the wrong one and promptly snapped all the heads off the screws when trying to take it apart to fix something.

[Munchskull]

Originally Posted by Cory

loctite works totally fine. Make sure you get the appropriate one based on the size gap it needs to fill. Also make sure to use the primer on both pieces.

648 is a primerless loctite.

[Cory]

Originally Posted by Munchskull

648 is a primerless loctite.

Primer is still recommended for 648, particularly for aluminum. It both cleans the surfaces and decreases cure time until maximum strength is reached.

[Mr V]

I do not recommend press fit bearings for a couple of reasons.

Too tight of a press fit or a hole that is not perfectly round can cause an increase in friction of the bearing and possibly cause it to fail sooner than it otherwise would. Bearing failure is another reason to not use either a press fit or a sleeve retaining compound. If the bearing fails and I have seen them fail then replacing it on a fully assembled robot can be difficult to do in a quick manner.

On the WCD drives I've been involved with the mechanism that retains the sprocket and wheel also retains the bearings. On those the chain runs were on the side of the tube facing the inside of the robot and the wheels are on the outside. Those are retained by either a bolt threaded into the center of the axle or an E-clip or snap ring in a groove on the axle. The sprocket and wheel then retain the bearings though you'll want a spacer between the bearing and wheel. Then if the bearing does fail you can remove the wheel or sprocket and slide the bearing out by hand, with the axle still in place.