Need to stiffen up the front end of the sand rail

I'm slowly chipping away at the to do list on the sand rail and need to figure out how to brace the front end. Right now I have the two lower rails just bolted to the beam to keep things located properly. I know usually people weld diagonal bars from the crossbar out to the front of the rails just behind the clamps like the blue tape in the first pic. My problem is I have an electronics box that will be going in that area as well as the battery. Having the diagonal bars will make fitting everything much harder. My other two ideas were either just welding one bar across just behind the beam or adding that bar then adding two more on either side tied back into the lower rails. Not sure if that makes sense so it's the blue tape in pics two and three. No matter which route I go the floor will be bolted to the bottom of the frame. I'm going to drill holes through the floor and into the frame then either thread the holes or put inserts in. I'm going to bolt it every 6-8 inches anywhere it touches the frame so it will help strengthen things also. The orange level and framing square are roughly where the electronics box will be.

What kind of deflection are you getting? What's driving you to stiffen it?

When I look at it, the first thing I notice is that you've got near-parallel tubes sticking out the front that are terminated in just clamps... Even tying the upper and lower tubes together with some kind of web so that the subframe isn't held on a self-sprung four-link seems like it would make the front end much more rigid.

As far as lateral rigidity, picture two doesn't look like it would do much of anything. Picture three is better, but would be much better again if you then triangulated the angled blue tape back to the same spots at the center rails as the first photo shows.

"Triangulation" that feeds loads into the middle of a tube in bending isn't really triangulation, though picture three at least shortens the un-triangulated run, I suppose.

I'm trying to avoid adding anything in where the electronics box is going. It is going to cause a bunch of other problems for actually building the box, limit battery size and a few other things. I need to figure out a "good enough" solution that's not going to bite me in the ass. 

In reply to EfiniMotorsport :

Sorry, I somehow latched onto the idea that the level was where the box would be, rather than the level/square area. Reading comprehension fail.

Any is better than none, I guess. Your photo three would at least shorten the unsupported arms, raising the "spring rate" of the flexing part...

You may be able to get more/better help out of others with a clear definition of the problem caused by the lack of bracing. Is it all about lateral flex?

How about boxing the corners of the existing cross-tube and welding a plate across where the level is, maybe it can double as the floor of the electronic box or battery box, whichever will go there. The plate thick enough to handle the torsional load but no wider than whatever you'll be mounting there.

Will the electronics and battery stick below the level of the bottom of the bottom tube? Because if not, I really like wlkelley's idea of welding plate there. Even just sheet material would add a ton of stiffness if you have a bead roller or put some folds in it with a brake. Add some dimple die holes in it that will double as "added lightness" and as drainage. If they will stick past it, what about a sheet or plate that has holes in it for them to pass through.

The bottom of the box will be the floor plate. The floor panel will be 12-14ga and cover the entire bottom of the rail. I like the idea of adding gussets instead of tubing. I wasn't sure if the floor being bolted to the frame (instead of on tabs) would add much to rigidity. I'm cutting all the panels for the electronics box tomorrow so I can take some pics with everything in place. 

Is adding an inch or so of height to the battery/electronics box, by running a couple of tubes for them to sit on, really going to cause you that much trouble? As flimsy as that's all still looking, I personally would rather have them supported by tubes with gusseted brackets than simply sitting on a bit of flat light gauge sheet...And tubes will be lighter than doing that area in plate.

How big is the electronics box?

Could you triangulate the frame using the idea in the third pic, but repeat it on the  tube by the pedal assembly to create a diamond shaped spot to put the electronics box?

That would stiffen up the front end while leaving a large area for the electronics box, you would just need to rotate the box 45 degrees so the corners of the box match the diamond created by the bracing. 

Weld a plate (1/8", maybe) to the bottom tubes. You get a floor, and brace in one. 

If it seems right, do speed holes, and a cross bar, like picture 2 at the same time.

If weight is a concern, a bead rolled sheet of say 18 ga. metal could do the same.

The floor will be one piece of 12 ga steel the covers the entire bottom of the rail. It's about 38"x84". Below is a template of the electronics box. It has to sit basically right where it is to clear the reservoirs, steering shaft  and tie rods and have enough room for all the electronics and the battery. I had to make it a little shorter than I expected but that does leave more room for bracing from the front cross bar to the bottom side bars. I'll basically be doing what I laid out in pic 3 but with longer bars. I'm going to have to find just the right size battery to fit it inside the box with everything else. Two fuse blocks, Raspberry Pi, Arduino 256 mega, Relay board, 5 relays, battery switch and a few other things. I did get the engine harness ready for the PET sheathing. I'm adding two cylinder head temp sensors, oil pressure and oil temp. All that data feeds to the arduino  and on to a 10" display. All the sensor wire are twisted pair and shielded. Shouldn't have any noise issues.  

I can't change the size, shape or location of the electronics box. I need the size and shape to fit everything and because of those it only fits in one place. It can't go any higher because it will hit the steering shaft and I can't shorten the box (to allow me to raise it) because the electronics won't fit. I need to figure out how to make the frame stronger with these limitations. 

EfiniMotorsport said:

I can't change the size, shape or location of the electronics box. I need the size and shape to fit everything and because of those it only fits in one place. It can't go any higher because it will hit the steering shaft and I can't shorten the box (to allow me to raise it) because the electronics won't fit. I need to figure out how to make the frame stronger with these limitations. 

Build a bridge going between your beam axle brackets and X-brace side to side, X-brace from your beam axle brackets back to your mid-bar (cross bar your steering column mounts to) on your front roll hoop. X-braces from beam axle to your plate on bottom, X-brace from back of plate to bottom bar under your roll hoop. X-braces from beam back to roll hoop on left and right sides.

That's how triangulation is done. Anything less is marginal at best.

I'm going to need a drawing of that. That's a whole lot of x's.

EfiniMotorsport said:

I'm going to need a drawing of that. That's a whole lot of x's.

Looking overhead: connect your two sides (L/R) top and bottom (box shape) where your beam attaches. X from where your beam attaches back to the base of where your windshield would be.

From the side: connect top and bottom rail (up/down). X from where your beam attaches back to where your door bar would be.

From the bottom: X from where your beam attaches to your 12ga. plate. X from where your plate ends back to where your pedals mount.

You will have to load your electronics from the area where your pedals are.

I think that's going to be WAY overkill. Yes it would stiffen the front end but between the added weight and complexity it's more than I need. I just need to make the front bars (in front of the bar running left to right in front of the pedals) stronger. Its either going to be a sideways K assembly or a bar just behind the beam with gussets.

Make your floor panel from 6061T6 aluminum about .090" and rivet it to the bottom tubes with Hysol epoxy and a rivet every 1.25 ". This will provide your structure and your floor in one piece.No folds and no tubes.

TurnerX19 said:

Make your floor panel from 6061T6 aluminum about .090" and rivet it to the bottom tubes with Hysol epoxy and a rivet every 1.25 ". This will provide your structure and your floor in one piece.No folds and no tubes.

Wasn't that how Lotus 7s were built?

If you shortened the passenger side foot well to only extend as far as the face of the pedals, rather than the end of the pedal box, and use that space for some of the electronics/battery...Might distributing those parts around a larger footprint free up enough vertical space to run the the better tube setup underneath?

In reply to Knurled. :

Yes and no. Yes they riveted aluminum to the tubes, but nothing as stout as I proposed for a sand rail. More like .048, and some english alloy that was more akin to 3003, and originals had no glue, so way less sturdy, but adequit for the intended use and life cycle.

Fwiw, this is how the front of the "lot lizard" rail was braced when I got it.

And this is how that ended up (not to say it wasnt functional, but it was added unnecessary weight)

At the end of the day this is how my front end looked prior to flooring (and my flooring was not a stressed member)

However the main difference is my front beam was fully welded to the rail so it became a structural member to limit flex in the front.   Not how I would have chosen to do it but it was done prior to my ownership.  This also means the bracing shown in the last photo wouldn't really work for you as it too is welded to the beam.   But I thought I'd share what was there for inspiration.

An "X" member is sorely needed here.

And a collapsible steering column!

JThw8 said:

Fwiw, this is how the front of the "lot lizard" rail was braced when I got it.

 

 

Man, that was such a cool rig...why did you get rid of it?!

Gingerbeardman said:

Man, that was such a cool rig...why did you get rid of it?!

I'm more a fan of building than driving.  Or at least purpose built (race only) cars.  So it had to go to make space/time/money for the next projects which were my tandem builds of the wifes CJ7 and my wilmac trike.  My only regret is I didnt keep the 2 liter motor from the lizard to put in the trike, but that would have been a fast way to hurt myself :)