Fender/Wheel arch horizontal distance from tyre

[grantstew8]

The fender/wheel arch design I have is based on a 50’s shape. where the tyre is inside the wheel arch.

There are lots of posts about the vertical height of a fender from the top of the tyre. My question relates to the horizontal distance from the wheel wall to the fender wall.
Any deflection in the wheel wall is typically at the bottom of the tyre, nearest the road surface. When a tyre is flat the bulge is at the bottom.
I image I could have the fender wall about ½” from the tyre wall.

(view from below the teardrop)

Does anyone have any concerns I’ve missed?


It’s probably going to come down to image.

The link is to a video of how I cut the fenders using a router http://youtu.be/GSNjullSfj8

Thanks

[angib]

A small gap (1/2" sounds right) will work with a torsion axle, as the wheel moves only up and down.

With a rigid axle on leaf springs, some more clearance would be sensible since each wheel can also roll sideways a bit - for example when one wheel is up and the other is down. Plus there will be some sideways flex in the springs and spring mounts.

[grantstew8]

Thanks, I thought it was the case. It's a torsion, so the movement is only up and down as you say.

I'll be making spars just like the main roof of the TD to fix the lid of the fender on.
I'm using an epoxy for the main body of the TD so I'll add a little glass where it joins to the body and on the external join.

[CarlLaFong]

Just be aware that a tyre (we call them "tires" or if you're from the south, "tars" ) will grow at high speeds, though half an inch seems OK, to me

[KCStudly]

Don't forget to make sure that you have clearance to get the tire and wheel on and off of the hub. If the axle arm drops down enough when you jack the trailer frame up, you should be good, but it would be a silly sight to get a flat (that's a puncture over here, not an apartment ) and not be able to change it out w/o hacking off your fender. If you are going for a low covered up look, and this looks like it will be an issue, maybe you can make the outer part of the fender removable(?).

Maybe it won't be a problem, but with any deeply shrouded fender it seems like a good idea to check!

BTW, I'm using bigger tires and leaf springs so I am looking for at least an inch of clearance at the sidewalls.

[grantstew8]

Thanks chaps. All valid point and I'll check in the morning. I'll jack the trailer up and confirm I can take the ti(y)re off. I'd feel like a real plonker getting a puncture and then having to cutoff the fender....

[aggie79]

KC brought up a good point.

The no load position of the torsion axle on my teardrop was about 1" lower than when the axle bore the weight of the teardrop. If I remember the tech specs correctly, there can be an addition deflection of 2" or so due to impact loads such as potholes and other sudden grade changes.

For this reason, I set the clearance from top of tire to underside of fender at 3" with the tire in the unloaded condition.

[grantstew8]

Brilliant information. thank you.
I've gone with an inch horizontally, half an inch is just too tight if I need to remove the tire/tyre and I've got lots of space to go with 3" above the wheel.

My son suggested that I make the wheel arches with roof spars, just like the roof of the TD after I'd put them together http://youtu.be/wYw9MwiLeRA.
His idea is much better than mine.....

I'll add some angle brackets, like right angled shelf brackets inside the wheel arch to give it some more stability/rigidity


The concern is for both for wind pressure, not that I'll be breaking the ton pulling a TD but @ss pressure of someone sitting/leaning on it