Alternative Cage Designs

[Trenon]

For what its worth my exocet is far easier to get in and out of than a sport / race as both the windshield and center bars make nice handles and there is nothing in the way of getting in and out.

[beardy]

I did something a little different from standard. See the build thread which has some frame pics.
mevowners.proboards.com/thread/7971/streetcar-named-broccoli-wa-usa?page=1&scrollTo=85970
My rationale was something more than the standard hoop options but easy to get in and out of. I don't anticipate doing anything more than a few trackdays at most.
Front legs and roof bars amounted to 1500 from external cage guy.
Its not perfect but more or less as I intended.
cheers
Mike

[nickmpower]

Aug 1, 2016 23:25:17 GMT kiwicanfly said:

Just had a cunning plan

As discussed earlier top side bar would be required for competition use but adding them neatly could pose a problem. Well when in place it would be Ok but when removed it could result in ugly fixing points exposed.

A sngle bolt won't cut it but using a taper boss and bush at each end will be impossible to assemble.

So..... imagine a taper boss in each end of the top tubes with the large end of the taper inside the tube, carry this taper profile through to a female boss welded into the hoops. Now have a male taper plug inside the top tube that can be pulled into position to lock everything together.

Hopefully this picture illustrates the idea. The green colour is the cross tube, the red a boss inside the hoop, hoop is blue. Pin is grey and shown in closed and open positions.




Same used each end of the cross tube.

Whether it would be certifiable I don't know but might be worth a poke and it would be significantly stronger than a bolt alone.

Yeah I actually thought about something like that, using a spring on the inside to make it pop out. I think the taper inset would also have to have a long cylindrical portion that extended into the tube to help support it. If I was going to use tapers I think I would just have the whole bar itself expand and contract. Are the tapers custom made or off the shelf?
The thing is these joints would only be loaded in shear if there was a direct impact to the bar, such as landing on a tree stump or guard rail. For a normal rollover the bar would be loaded in compression. I calculated the shear strength of a half inch bolt to be 20,000lbs. So if the bar was bolted on each side it could hold 40,000lbs before the bolts broke.

[kiwicanfly]

I would disagree with the need to have a cylindrical section inside the tube, the two female bosses would be welded in place in each tube and the taper pin would lock against both bores. Any parallel section inside the tube would need to be undersize in order to allow free movement of the pin thus would not offer much support.

Of course it all depends on the accuracy of the tapers in angle, length and diameter. What I did not add to the drawing was a bolt to pull the taper pin into place and lock tight, the drawing I did is to scale and utalises a 10mm bolt, the angle needs to be above 16 degrees (from memory) or the plug would self lock and this is something you actually don't wont as you would have difficulty separating them later.

To be honest making the male tapers lock into both female bushes at the same time is not that easy, not impossible but definitely not easy.

The other thing that might be required is a means of stopping the male pin rotating whilst tightening the bolt, in theory it should not but a damaged thread might cause an issue.

The taper bushes/pins are certainly not off the shelf.

Making the bar itself expand and contract would result in low strength, everything has to be locked solid to act as a single structure and I can not see how this can be done with an expanding bar as a lateral impact would compress it and a side impact would fail at the joint.

There's is no such thing as a normal rollover, this implies that you are only planning to have certain types of incident. The fact is that no matter how more unlikely one type of incident is over another you have to cater for all types.

Consider the video on this link and the damage to the car, if the car had been one length further forward when he hit the fence the side impact would have been replaced with lateral impact from rolling end over end down a hillside. However if the roll cage had been constructed for lateral strength only the driver would have been severely injured as the post would have entered the car more.

mevowners.proboards.com/post/88827