Frame Critique

[ws6vert]

I have some time between classes this month and scratched up this basic design. It comes straight from the KTM AX photos, with modifcations. Let me know what yall think, and if the design is worth-while, or can be made worth-while. It is not completely finished, I have only recently finished the design of the rear tubing and am not sure I like it yet.

All comments and suggestions are welcome. (had to upload to photobucket b/c attachments didnt work.)

[Gene]

Interesting. I would not feel safe because it is too open IMO. Guess it depends in intended use . . .

[El Toro]

I would be concerned about how open the front of the cab is just forward of your head..imo
Spencer

[Mopar]

i dont like the bar directly over your head....

[ws6vert]

Tough crowd, haha. Thank you all for ur input. I can see where the open design would have its issues if you were improperly restrained and came to a dead stop at over 40 mph. In designing it, I thought about these issues, but my intentions for any buggy I build is for trail riding and mudding. So with those intentions in mind, the open design doesnt present too many flaws, as most trail rides aren't done at break neck speeds and vision is important especially when u want to see all that mud flying at you. (please let me know if im wrong in this line of thinking). Also I can easily adjust for head clearances. There is as much as 6in. between the top of the seat and the upper bars at the moment. I plan to increase that anyway as soon as I find a good solidworks dummy to test fit these clearances.

On a more serious side, what about the overall rigidity of the design or complexity of the tube bending. Do you see any flaws there? I have yet to think very hard on the rear section so im sure there is room for improvement there. The design is planned to be based around trailing arms and swept back axles if that helps.

Also here is a pic of the KTM AX if you have never seen it:


Remember this whole design was pretty much thrown together just from the pictures. Its certainly not your typical mini-buggy fram design.

[chuckorlando]

I love the trails. Unless there clean trails I see you getting sla[ed with some limbs. My cage is constantly used as an overhead brush guard

[minibajaman]

Well it certainly looks pretty cool and interesting, but IMO it's not a very practical frame from both a safety and building perspective.

Originally Posted by ws6vert

Tough crowd, haha. Thank you all for ur input. I can see where the open design would have its issues if you were improperly restrained and came to a dead stop at over 40 mph. In designing it, I thought about these issues, but my intentions for any buggy I build is for trail riding and mudding. So with those intentions in mind, the open design doesnt present too many flaws, as most trail rides aren't done at break neck speeds and vision is important especially when u want to see all that mud flying at you. (please let me know if im wrong in this line of thinking). Also I can easily adjust for head clearances. There is as much as 6in. between the top of the seat and the upper bars at the moment. I plan to increase that anyway as soon as I find a good solidworks dummy to test fit these clearances.

The issue is not stopping from speed with improper restraint, it is the fact that there is no roll cage member outside of your head. If you roll over, your head could make contact with the ground, or worse an object like a tree stump or rock. Since you plan on trail riding vs. duning, these are real concerns. Vision is not an issue with a normal style roll cage, you won't even notice the tubes there. You should leave at least 4" clearance from your helmet to the overhead roll cage members.

Originally Posted by ws6vert

On a more serious side, what about the overall rigidity of the design or complexity of the tube bending. Do you see any flaws there? I have yet to think very hard on the rear section so im sure there is room for improvement there. The design is planned to be based around trailing arms and swept back axles if that helps.

Strength wise the frame looks ok, triangulation is used extensively. That upper U shaped member behind the seats is worthless and will compromise the frame strength in that area, as that roll hoop is one of the most important parts of the frame. Just run the upper tube straight across. The biggest problem with manufacturing is some of those long tubes with multiple out of plane bends will be extremely difficult to make on a manual bender, but might be a good job for a CNC bender.

I attached an image of how I think you could greatly improve safety without changing your style/look too much.

Originally Posted by chuckorlando

I love the trails. Unless there clean trails I see you getting slayed with some limbs. My cage is constantly used as an overhead brush guard

I agree, my cage is always keeping branches out of my face on trails.

[nutz4sand]

You might not be going break neck speeds but trees often win battles with 2 ton cars doing 90 mph. A light buggy will go from 40 to 0 NOW against anything but a sapling.

I agree the roll cage is not enough for woods riding. The desing you are using as a concept and has not been proven in real world harsh testing. It looks badass. But if it leaves you in a wheelchair after a wreck its not worth it.

Go look at the SERIOUS woods buggy crowd. They do sooo much more rollcage than the sand crowd its not funny. But when they "oops it" and roll over down the side of a large hill they usually walk away. But they have virtual cages covering them to stop trees and rocks from ALL angles they can.

Even a simple trail ride can lead you to the tops of some mean hills you drive along and if a rut or log tossed you over the edge you might be going downhill faster than you ever planned to drive off road. Maybe on your roof. More rollcage would be really nice to have at that moment.

On your design I am not fond of the hump thats under your legs. It LOOKS kinda cool. But is a place to hang up on a log or worse. Its also a potential bend point made worse if you hit something.

I am also not a fan of the gap down the middle top. Again it LOOKS cool. But it would be a MUCH stronger unit to simply connect the top bars at a few places. But hey its your neck :]

[ws6vert]

Good suggestions from everyone... I'll take all of this information and give it a redesign, specifically around the upper roll cage, when I get some time.

nutz:
The hump in the middle is to allow your legs to sit comfortable at a nice angle to the pedals rather than bent constantly on a flat surface, like a foot well. I could potentially add a few braces to the underside in this area to skirt away any logs that may want to jam in there. With the amount of bracing and triangulation already present, it would have to be a serious shock to the front or rear of the frame to bend in that area. But i will certainly consider alternatives.

Hopefully with all these suggestions I can convert this concept into a functional design. Please keep the comments coming and hopefully together we could make this a possibility. I mean at least it has potential! right?

Edit: Can anyone tell me how to attach pictures so that they are thumbnails until you click on them?

[nutz4sand]

For the time and trouble to build the hump into the bottom of the frame one might consider just a flat frame with a leg rest added in.

Your desgin IS quite different but most any buggy I have ever gotten into anything in the way of the legs was a issue usually on most. Your layout may make getting in with the hump not an issue.

Most of the time I have just seen well placed foot rests and angled back seats to get the angle for comfy legs so I did not really think it was for that when I saw it. Was not sure what it was for per say just on seeing it.

But I do know what you mean by a low seat with a flat layout of the legs. No fun at all.