how to jack up a 48 curtiss wright clipper 5

what is the harm with using the axle?

No matter what you "might have heard" they have no engineering basis for telling you that you cannot jack up the trailer by the axle.  It would be just my guess that maybe you have paraphrased what might have been actually recommended?

You do not want to jack up the trailer weight "in the middle" of the axle.  You do want to place the jack under the spring and only jack up one side at a time.  You need to fully support that side with quality jack stands before you go to the second side to jack it up.  Again, you need at least four jack stands to support a trailer.


Your trailer was built with what is called a Spline Frame.  It has a "single round tube" (about 4") going down the center of the trailer.  It usually goes from the coupler back to a boxed section over the axle(s).  Ribs come out from this spline and connect the sides of the trailer walls and a perimeter steel frame.  Spline frames were used by several manufacturers in the early 1950's for a short time.  There is a reason they did not continue this frame style.

The trailer has, or originally had, jack pads under the strong framing areas.  You can place a jack or jack stand under any of these jack points.  Spline frames were used on trailers that also had belly pans.  Many (maybe most) times these frames are heavily rusted due to condensation inside the belly pans.  It's best to grab firmly the coupler jack and try to see any twisting movement of the spline frame when you move the jack "side to side".  Any frame movement is bad and would require the belly pan be removed for closer inspection. 

John Palmer

The Spline Frame design is not a trailer brand specific thing.  Several brands used this marginal design.  I called it marginal because history will show how quickly the trailer industry abandoned this frame style after only a few years and never revisited the design.  I have rebuilt a 1953 Silver Streak with this frame style about six years ago on a trailer that is towed yearly from So. Cal. to Montana and back.  If I had it to do again, I should have just built a new conventional perimeter under the original body.  It would have saved time, money, and produced a more durable finished product.

One issue to consider it that the various riveted skin trailers, that used the spline frame design usually have very small wheel (fender) cutouts, some even have "no cutouts" making tire removal on the roadside sketchy.  This is why in my original post I suggested the trailer be supported by "quality jack stands" after you have it jacked up.  Once the trailer is jacked up, AND you have supported the frame on stands, you lower the jack and axle to allow the wheel to drop down for easy(er) removal.  All of this should be done while still connected to the tow vehicle to stabilize the trailer movement.

John Palmer