Quote:
Originally Posted by Joseph Smith
I've been investigating some new design and construction methods that my team hasn't explored in the past, and I really want to try assembling the frame and important structures with machined gussets and bolts. I have a few questions for teams who have used this construction method. In this scenario, I'd be using two gussets, top and bottom, to create a 90 degree joint between two lengths of rectangular aluminum tubing, all 1/8" wall thickness.
1. Is it better to put a long bolt all the way through and use a nut on the other side, or to tap the gusset and tubing and use shorter bolts?
2. If a bolt all the way through is used, are large washers needed to spread the load to prevent the tube from being crushed?
3. If the parts are tapped and a short bolt is used, would it be preferable to tap both the gusset and the tubing or to drill clearance on the gusset and only tap the tubing?
4. Is locktite a necessity with the tapping method?
5. What has been your overall experience with this method of construction? Pros/Cons?
Thanks!
I should clarify, with the pretapped method, we would be using machine screws or something of the sort.
Clarification #2: We have used a lot of rivets in the past, and do like them for certain applications; however, I'm specifically interested in trying out bolts on the critical parts of the frame- primarily drivetrain- where it can see a lot of stress due to collisions or hard driving. These would be parts that we shouldn't ever have to disassemble or replace between matches (fingers crossed) so I'm not really concerned about the speed of installing/removing them.
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We've used this construction method for the past two years on our west coast drive base and on some superstructures. Here's specific answers to your questions.
1. Mostly tapped the 1/8" tubing and used short screws. Our build standard is based on M6 socket button head screws.
2. We use bolt through or rivet nuts for mounting the superstructure to the base. We typically spread the load with washers for heavy structures like our tower this year.
3. We used tight clearance holes on the gussets and only threaded the tubing.
4. Loctite is necessary.
5. Pros / Cons: This method is slightly heavier. Not much of an issue for the drive base, but superstructures with 1/8" tubing can add up even with pocketing. We used this method because we had the tooling not necessarily for reliability. But it does hold up to competition abuse.
One disclaimer - We are buying the tooling for 3/16" rivets next year. Just never got around to before.
Let me know if you have any other questions.
David