Skin repair using an English Wheel

[sgschwend]

This is my third go around with fixing AS skins using an English Wheel. This is the biggest project to date: five of the exterior end cape (all the skins from the rear window up).

Here is a picture of a couple of the panels with damage, all five had similar problems:



We purchased the trailer knowing the rear end was damaged. The damage was not hail as was suggested but likely the trailer was backed into a tree. After which somebody tried to push the dents back out. There was very little frame damage, which I think tends to eliminate damage from a falling object.

The English wheel can shift the metal around with little change in the panel shape or size. As you can see four of the five panels have been reinstalled. The benefit of this method is the panels will be the same age and patina.

Here is the results from working with these over the last three days. The last skin still needs to be straightened and installed. There is still clear coat on some of the skins, once the Olympic rivets are completed then we will strip the top half of the trailer, polish and then apply coatings. I think we will add a roof coating.

[DanB]

Nice work! Love to see photos of you using the tool.

[sgschwend]

I will give it a try, vid might be better, it takes two of us to run the machine.

[Ag&Au]

I have always been told that when aluminum was dented it stretched and could not be worked back to shape. Is your work proving that to not be the case, or is something else in play here?

Ken

[Marcher]

Have always wondered if an English Wheel would work on cleaning up the dents on the banana wrap of our '75 Globetrotter, could you provide some details on the technique you used to prevent stretching the aluminum any further.

[sgschwend]

I did get a couple of pictures taken and will get them loaded tomorrow. To answer the question about size changing, for all practical purposes the skin size does not change. I have reinstalled four panels using the original holes, to locations that were not wheeled, such as all the outside edges and window framing. In the description of fixing a dent you will see a statement about the wheel area needing to push against the unwheel area around it so that it can move up. The unwheel area is still the original size, hence the wheeled area can locally expand and push against it.

I have completed repairs using annealing and without annealing. A simple dent would likely be able to fix without annealing. When you work the material you can tell if it is moving easily and therefore does not need to be annealed.

The next thing to know is that I am almost always using the finish setting which is a very light pressure hence very low shifting of the size of the part. If the part was the correct shape this setting would likely be the same as the aluminum thickness.

Folks that are experts, which I am not one of them, work their material and then the last step is to switch to a light pressure and run the part to finish it. I also use the largest radius anvil, which is least aggressive. The top wheel is flat, the bottom wheel is called the anvil and most machines come with a range of curves.

I have found that the easiest way to fix a skin is to address a small area at a time, find an area that needs fixing and roll that part. Move around the skin fixing each problem spot. This is not a common method, but again I am not making a compound curve part I am just returning certain areas back to the correct curve.

I have also found it is better to move all the high spots down first (which means run the part upside down), then turn the part right side up and raise the low spot. It does go amazingly quickly.
Image moving a high spot down:


To fix a dent: Imagine a six inch round low spot, dished down, a typical type of dent. This defect is much smaller than the skin and there is lots of skin around it to maintain the total skin shape, fixing this will not change the size of the skin. The surrounding material is what the wheeled material will push against to allow it to rise into place. You would put the part in the wheel right side up, with a low setting you would roll back and forth starting from one edge and moving 1/2" over after each pass stopping at the other side of the dish. The material will move up where it was wheeled.

[Ag&Au]

I'm thinking you should go into business fixing dented Airstreams.

Ken

[sgschwend]

Here is a short video (52s) of removing two places where the skin is above the desired plane. Running the part upside down over the "high spots" will shift them lower.

http://vid212.photobucket.com/albums...psqzxn4ii3.mp4

[sgschwend]

Well this project has taken three weekend to get the five skins in the back removed, straighten, and re-installed. I purchased a used Pasar Amprobe Leak detector, and tested the new skin assemblies and everything passed. For added leak prevention I installed the skins with AS seam sealant between the overlapping skins, and then on the inside spray undercoating.

There is plenty left to do but those tasks should be easier to do. The next steps are: shaving of the rivets, the painting of the roof, stripping of the belt line up of clear coat and restoring the aluminum then new clear coat, removing the blue tape, and lastly return the interior.

Here is a picture of the rear assembled, the rear awning is off to support the roof painting which will included the center top skin front and back.

[Aerowood]

What make is your English Wheel?

[sgschwend]

It is a China made copy of a Baileigh design. It has a 28" throat. Taking dents out uses very low pressure so I would think just about any wheel would work. I picked it up on that International online auction site. I offered $100 less they gave a 50 bucks discount.

I did measure the wheel spin accuracy and found it to be good, which is the measurement of the wheel roundness and axle center accuracy. If the wheel was inaccurate the pressure would modulate.

http://www.baileigh.com/english-whee...FQtqfgodrOwBUw

Pros and Cons
Cons:
you need to remove the skin, and strip it,
you may need to refinish the outside, in my case the upper three need refinishing the two side one just need some clear touch-up work.
need to install it, however the holes will match up so it goes fast.

Pros:
easy to remove dents,
metal is the same vintage as the trailer,
low cost,
can make patches to match any trailer curves,
with the annealing step you can redo a repair,

How about time:
Removing, striping, fixing, installing. I have heard one shop says they charge 6 hours per skin (they don't strip or fix), but they do need to drill.

For me I could easily do the above process in 6 hours per skin.

In this project I remove the 5 rear skins above the belt line and also the rear window. The window removal took three time the work than to remove a skin. The wheel time was nearly the same for any of the five skins.

In summary, drilling out the rivets 1 hour, breaking the inside bond 30 minute, stripping 2 hours, wheeling 30 minutes, installation 1.5 hours: total 5.5 hours.

[Aerowood]

I tried using the HF version and it was junk, the lower adjusting screw assembly and roller clevis had to much slop and it would not stay in adjustment. I have looked at the type you have and was curious as to it's quality. I had the opportunity to use a high quality cast iron unit a few years ago at Cascade Aerospace in Abbottsford BC, and it was an absolute joy to use.

[ALANSD]

very interesting to watch the video. Cool stuff

[Lumatic]

Originally Posted by Ag&Au

I have always been told that when aluminum was dented it stretched and could not be worked back to shape. Is your work proving that to not be the case, or is something else in play here?

Ken

You can get some dents out all of the time. You can get some dents out some of the time. But you can't get all dents out all of the time.

Never have been able to completely get out a dent with a crease, but have been able to make it look better.

Don't know how an english wheel will work on a crease.

[mb-austin]

I see that Northern Tool also sells an english wheel, I would pick that over HF. I wonder how well it might work: http://www.northerntool.com/shop/too...0087_200660087

$329 plus shipping, can avoid shipping by having delivered to store. Must buy extra lower wheels separately (comes with one)

[sgschwend]

I would agree that removing dents to automobile quality is very difficult and time consuming. Airstream skins in my opinion are not in the same league due to the method of fitting them together or being attached with rivets. My guess is that we know this and accept those changes as "normal".

As to creases, if you had the skin off and you annealed it then the crease would likely repair to a point that would be better than acceptable. I annealed most of those 5 skins. Annealing really does give the metal a chance to release the dent caused stresses and also softens the aluminum so that it moves easy.

Yes China made equipment is more like a kit, you purchase it and then build or rebuild it. That is why I checked it for accuracy to ensure it would spin correctly, don't quote me but I remember something like +-.002. The anvils in my machine are very nice, no complaints there.

I did make some patches to cover where the old antenna was, and at the place the tree smash the rear skins. To make the aluminum circuit into a compound bend I needed to turn the power up to shape the curves I needed to match the location.

[Keyair]

Not a Hijack, but I am into this thread.

Bought mine from an estate sale 2 weeks ago.
It was about $50 or $60... I sale about because I originally agreed $70, but piled a bunch of other stuff around it and ended up getting a package deal with a ton of other tools..


It is a HF unit, but it is one of the better, welded ones and Identical to the Baileigh EW-28, which is $800...
I only got one lower anvil, but grabbed a set from HF for $55 with a coupon.

So, it is my understanding that these are good units but need some fettling and mods, which I am ok with, at about $100 invested so far.

The first thing I did, was check the upper wheel runout, and it was not good.
I made a mandrill, and chucked it up in my lathe.
Breaking thru the hard chrome layer, took a carbide tip, but it trued it up and allowed me to get a better finish on it.



That done, I set out to learn to "Wheel", which I have never done before, but I am normally a quick study.
Decided to do a test piece that would be a smaller scale test for a rear wrap.
After a couple of hours, this is what I made...



A quick buff showed me how it was...




The machine does need some stiffening by adding a backbone, but this small test was done without it.
Small investment, lots of potential!

Quick video of test piece...

[sgschwend]

Yes, it is a great skin repair tool. I found that the five repair skins in my rear end cap returned to the same place after wheeling. Needing very few Cleco clamps before riveting.

I must admit I now look for damaged AS to see if I should purchase to restore the damage skins.

Looks good. The trick for me was trying to match the original surface finish. I ended up hand sanding with various coarseness of steel wool.

Repairing parts takes practically no pressure.

I did make three patches and found that the pressure would distort the backbone.

[PLVMB]

I have a coach builder friend who worked this out.

[StevieB]

A few additional options and "How to do" stuff.

http://search.eastwood.com/search?w=english+wheel