Tiretail design

[twinch]

I have been designing a tiretail for this season and I just wanted to get people's input. Here are the details.

This design I have gotten down to a touch more than 15lbs and I believe it will be stable and strong. I am using A-36/M45 square tubed steel. I am not willing to go alluminum or any other more exotic metal because I am hoping to make this for less than 40 bucks.

The mainsubframe is 1 1/4" square and fits into my receiver hitch(which is a Curt and has a tongue wieght of 250lbs). All other frame pieces are .75" square tube.

I have a sheet of .050" steel reinforced with a 1/4" keystock frame to deflect exhaust so it does not melt the tires.

The tires will be held down with a simple tiedown strap.

Easy peasy.

[darcyw]

you'll be bolting it together or welding it?

i like the air foil in the front.

darcy

[twinch]

Originally Posted by darcyw

you'll be bolting it together or welding it?

i like the air foil in the front.

darcy

Don't you work Darc? Wait, why am I not at work...Oh crap it's Wednesday isn't it?

Yah that airfoil is pretty sweet. It makes it go faster. But it's actually to defect the car's exhaust away from the tires.

[13inches]

The normal tire tail all the Miata guys use tends to block the rear license plate and most of the tail lights. You may want to account for this in your design.

[Doug Stark]

I'm sorry, I don't get this design at all? Where does the engine go? I understand the increase in grip however. What class will it race in?

Ok, enough questions, off to therapy.

[twinch]

Originally Posted by 13inches

The normal tire tail all the Miata guys use tends to block the rear license plate and most of the tail lights. You may want to account for this in your design.

Excellent point with the license plate and lights. I am hoping that the design is low enough to allow the third brake light and also the regular lights to not be fully blocked.

I'm going to need to mount the license plate on the tail itself. Ack...damn road laws.

[twinch]

Originally Posted by Doug Stark

I'm sorry, I don't get this design at all? Where does the engine go? I understand the increase in grip however. What class will it race in?

Ok, enough questions, off to therapy.

Bwa ha ha. Nice.

[Travis]

Looks like the wheel lip contacts the frame which would cause paint damage to the wheel. Even if you put some rubber in there, I think you'd still mark/scuff the wheels.

If you shorten the distance between the front and rear bar, the wheel would sit higher, and perhaps only the tire would contact the frame.

[13inches]

How are you planning to deal with wheels/tires of various widths?

[twinch]

Orginally I was going to go with something adjustable for different widths but since I am strictly dealing with 225 width tires I have it with a bit of tolerance. I won't be able to go much wider than 225. Perhaps a 235 will fit but such is life.

I'm not concerned about scuffing rims. I could maybe spray Rubberized Undercoating to help minimize scratches though.

Tomorrow I go to Metal Supermarkets to get this stuff. Unless there are any major concerns from anyone. Am I right that welding would be stronger than using bolts to secure this thing together?

Oh, Darc, I forgot to answer your weld/bolt question. It will be welded because from what I have read, stressed frames that are bolted, the holes start to stretch and the bolts start to loosen. Also, holes are a weak point in stressed members and the reduced amount of material can create issues and fatique could create cracks and then...tires all over the highway.

[13inches]

It seems like a lot of work for something that limits you to only one specific tire size. You can't move a spare set for a friend, carry your old snows to get new ones mounted, etc etc.

I'd re-think the design to make it a bit more modular.

[twinch]

Originally Posted by 13inches

It seems like a lot of work for something that limits you to only one specific tire size. You can't move a spare set for a friend, carry your old snows to get new ones mounted, etc etc.

I'd re-think the design to make it a bit more modular.

It is limiting to anything that is larger than 235 but I was thinking that it's easy enough to fit shims in there for anything smaller. I can easity make it adjustable by adding a few inches on the cross members drilling a series of holes and using bolts to lock them down. Thinking about it I may actually do this now. You make a valid point. Give me a few minutes and I'll revise the design.

[twinch]

Here is the revised design

[Ujjwal]

Make sure you analyze it for torsion and add gussets if required. If you're only welding it with fillet welds to the main hollow structural section, it looks pretty weak to me, especially in fatigue. It looks like something that is on a teeter-totter.

[twinch]

Originally Posted by Ujjwal

Make sure you analyze it for torsion and add gussets if required. If you're only welding it with fillet welds to the main hollow structural section, it looks pretty weak to me, especially in fatigue. It looks like something that is on a teeter-totter.

Yah there will be gussets on all cross members that attach to the main central beam. Thanks for the suggestion. Glad i put this up here to get opinions.