LOSI LST XXL Conversion ideas - RC-Monster Forums

brian015 · 03.20.2010, 07:39 AM

Those one-piece rails are going to be your most difficult fab work. I wonder if they're worth it. The weak point in your three-piece lower plate is obviously at the joints (and what you said above about sandwiching all four layers at that point with M4 screws sounded semi-convincing to me

). And it's at that weak point that your one-piece rails have their kinks. I'm not sure that turning your previous three-piece rails back into one-piece rails is going to add any rigidity to the chassis. I imagine the kinks in the rails would allow the rails to bend up and down at that point (where straight rails would not). So, I don't know if it's worth all the effort to make them.

Those are my thoughts trying to imagine how it would work when stressed - I don't think the one-piece rails would be a great advantage over the three-piece rails in reducing the stress on the CF top plate.

My vote: try your previous plan (3-piece bottom plate and rails) and if it fails go for a one-piece bottom plate.

So - when are you expecting to get your truck? (or is this just an elaborate thought-experiment?

)

JThiessen · 03.20.2010, 12:26 PM

Look at your chassis from the side. Now imagine a load being applied from the top. The chassis will bend downward in the middle, forming a "U" shape. With a solid piece running from front to back, the stresses in the chassis are linearly distributed through the member. When you have changes in shape, those stresses are passed through the most direct path. In your case, it will be through the fasteners and the holes for the fasteners. Now remember, you are looking at it from the side....you only have a single fastener line when looking at it from this direction. All those stresses are going to be passed through that fastener, and the thickness of each SINGLE piece of material. I'd predict an immediate failure - first at the bottom most piece - it will try to pull the fastener forward though the hole. The fastener being harder, will tear through the aluminum. Give your self at least two fasteners at each joint when looking at it from the side, maybe three.

mistercrash · 12:34 PM

For now, it's just trying to come up with a nice electric conversion that looks factory made. I really want the LST, when will I be able to get it is unknown

We just bought a new and bigger house and we are still unpacking from the move three days ago

Lots of work to do around this house but I still want to squeeze this truck in.
As for the three piece bottom plate, it is no different than the stock truck, the XXL uses a rear and front skid plate and a middle one that are not touching each other as far as I know. They all look separately secured to the chassis rails. What I show in the last movie are three bottom plates that overlap each other to form a flat bottom. This is because the center plate would be lower than the stock one. At the same level with the front and rear plates. The center plate also houses the batteries so the lower it is, the better for a low CG.
With the help of a band saw, the one piece chassis rails should be fairly easy to make with a bit of planning. The hard part might be to find the raw material to make them at a reasonable price. I still don't know how high the stock chassis rails are, if they are 1.5 inches high or less, I should be able to find material to fabricate at a good price. If they are higher than that then I might have some difficulties.
Thanks for your feedback, I appreciate it.

JThiessen · 12:53 PM

On the stock chassis, the plastic rail and the top plate do all the load carrying. The center plate keeps the lower rails from spreading apart when a load is applied. The front and rear skids aren't part of the equation.

The stock rail is something around .983 thick in the center - I havent measured the ends. Probably somewhere around 1.25" or so.

I went back and looked at your vid again. For some reason, I thought that your center rails were three piece.....sorry!

What CAD are you using? I might be able to send you my CAD files.

mistercrash · 02:00 PM

I'm not using CAD, I draw to scale with CorelDraw and then export the drawings in jpeg to make the little movies. CorelDraw lets me export whatever I drew in a lot of formats including DXF and DWG AutoCAD files. If you want to send me your CAD files I can just download some free CAD reader off the internet to see them. Once I see the measurements, I can duplicate the part in CorelDram but only in 2D. Thanks.

Ray
raymondduchesne@sympatico.ca