Ordering new Axle - Help with Angles

[jdconnel]

OK. I have made a lot of calls, learned a lot on axle specs and info.
I finally have everything together except one piece of info.

What I have about to be ordered:
Axle Capacity: 2200 lbs.
Hub Face: 63.00"
Outside of Frame: 48.25"
Bolt Pattern: 4 on 4”
Brake Option: 7” x 1 1/4” – Electric
Lubrication: E-Z Lube®
Tubing: 2.17” OD Square (#9 Dexter spec)
Bracket Profile: High
Bracket Orientation: Reverse
Side Mount Hanger Kit: Yes
I am running ST175/80R13 tires.

OK. Last But not least.
Start Angle Degree.

My current arm measures 10 degrees up, but it's toast. I have found other threads reporting this angle on a dead axle.

If I go with 10 degrees down (and I believe that was what scamp used back in 1977), that would give me 2" of lift from my current state. The axle is 8" off the ground now. If I go with 22.5 deg down, I gain 3.5" or so.

I have seen some pictures of 22.5 degrees and it looks high!
Although I'm low now. 3.5" doesn't seem like a lot.
Am I over thinking the extra inch?

[Eddie Longest]

What is the square tubing used for?

[jdconnel]

That's just the size that Dexter quotes.
Here's a picture of what I have in currently.

[Jack L]

You can also specify what you want the torqueflex tension to be. The #9 is a 2200 pound axle but the suspension can be set to whatever works best in your trailer.


For example, you might want the suspension set at 1800 pounds. It's the same axle with less tension on the rubber torqueflex system. The max is 2200 pounds but might be too much for your trailer.

[jdconnel]

When I called scamp they mentioned 2000. Although, I know they've moved away from Dexter.
Most other swaps I've seen, most people seem to be going with the 2200..... ?

[jdconnel]

Pictures always help.
Here is what is currently there...

[Jack L]

Originally Posted by jdconnel

When I called scamp they mentioned 2000. Although, I know they've moved away from Dexter.
Most other swaps I've seen, most people seem to be going with the 2200..... ?

The #9 is a 2200# axle, which means it has a maximum capacity of 2200 pounds. The Torqueflex system uses rubber inserts in the axle tube and they are what provides the suspension springiness Think of this as the springs on your car. Heavier springs might not be necessary, or they could be very helpful. Depends on the application. The Torqueflex can be ordered with what ever springiness you need. It will be a #9 with a suspension fine tuned to match the trailer. It's just how much tension they pyt on the rubber inserts.

[jdconnel]

Any recommendation on what to set the tension to for a 1977 13ft Scamp?
No idea what the weight is. I would think targeting 1500 when fully loaded up.

[jdconnel]

I found this advice from a Dexter guy:

If you put a 1,000# trailer on a 2,000# rated axle, you're not going to get much "squish" and/or "settle". Only spec your Load Rating at about 30-40% more than your spec'd or estimated NET weight.

I expect loaded up my camper will be about 1500# with gear.
+30-40% puts me at 1950 - 2100.

Not much tuning it would seem if that all holds true.

[Borrego Dave]

Originally Posted by jdconnel

Any recommendation on what to set the tension to for a 1977 13ft Scamp?
No idea what the weight is. I would think targeting 1500 when fully loaded up.

I checked the "trailer weights in the real world" thread and 15-1600# loaded looks like your target weight.

[Jon in AZ]

New Scamp 13s use a full-rated 2200# axle, probably because they can be heavy if fully equipped. The options list is a lot longer today than in 1977. Seems like 1800# or 2000# would be about right for yours, unless you are planning some significant remodeling.

As to the start angle, you have to ask yourself what you are trying to accomplish. Raising the trailer comes at a cost in wind resistance, stability, and step-in height. Just the new axle alone, same start angle, will probably give you an inch or two. 22.5-degrees down angle sounds pretty extreme to me.

[jdconnel]

I am leaning towards my original 10 degree down.
That will raise my camper 2.5" from its current state. (22.5 will raise is 3.5")
I think this looks correct and I like the smaller angle for travel.
That means my step in height will be 12.5. Most than fine.

My axle is leading currently. It is also stuck in the UP position. Measured 10 degrees perfectly, so I have a good baseline measurement comparing dexters +10 to it's -10.

When I called scamp they said all they do now is 22.5. Internet searching said they used different angles back int the day, but the young guy (I think) I talked to stated he only knew of the 22.5.

[Jon in AZ]

The current 22.5 is 22.5 UP. The axle tube is lower on current trailing arm installations because of the drop-floor.

[Scamper Jim]

JD,

It’s easy to reach the weight ratings with some large coolers, canned food and other stored goods, water tank filled, double propane tanks and larger or double batteries, solar panels, kids toys, and on and on. It doesn't take long for it to just happen.

I installed the 2,200# rated, 23.5 degree down axle. The weld-on bracket will raise it a little more also. It raised the trailer, but also gives longer torsion life before it sags that low again. As Jon said, check with Scamp to see what they installed back then and why.

The new height will have a different feel regardless of what angle you go with so will probably use a step-stool to make it easier to enter and exit anyway.

I would consider going to the 5-bolt pattern. It is the newer style and wheels will be easier to find.

[Civilguy]

James,

I don't know what angle Scamp used, but this link might help you review the options. It indicates the resulting "heights" for different start angles based on no load, full load and shock load.

http://dexteraxle.com/i/u/6149609/f/...nformation.pdf


Over time, particularly if you don't take the weight off the axle in storage, the internal rubber will get compressed.

[The Minimalist]

Have you downloaded and read the Dexter Applications Manual from their site? You said you spoke to a Dexter guy. Was he at a dealer or Dexter?

I would suggest that you read the manual and make a list of questions. Then, speak to someone at Dexter. Ask the right questions; get the right answers.

I don't mean to cast aspersions on any of the previous answers. They are all good. But they are based on personal experience and opinions.

You are going to be living with this thing for quite some time, so it behooves you to benefit from Dexter expertise.

I say all of this because, in rereading the posts, there are a number of exchanges regarding trailer height, ground clearance and such. Per paragraph 4 on the second page of "Trailer Design Considerations" begins, " Torflex axles ride performance is at it's best when the torsion arm is at or nearest the horizontal when the vehicle is loaded at it's rated load.....". It then goes on to explain the how the geometry of the system is effected as the down angle changes.

From this, I'm gathering that down angle should not be used to determine trailer height, ground clearance, etc. Leave that to the wheels and tires.

The real key here seems to be getting a realistic picture of your expected loaded weight. "Trailer Weights In the Real World" is a good starting point. Ideally, you would have the trailer weighed and then weigh all the items you plan to add and to pack. This seem like a lot but, as said, you will be living with this one for a while.

Lastly, you may want to consider larger brakes. In several recent threads, Scamp owners have mentioned that 7 1/2 inch brakes can't be locked up on the highest controller setting. This means you have no leeway in controller adjustment. The normal procedure for proportional controller adjustment is to set the power at about mid-way and then, driving 20-25 mph on a dry roadway, push the manual control to max. If you get lockup, reduce the power setting to just before lockup. If you don't get lockup, raise the setting. When you achieve lockup, back the power setting back, just short of lockup. Recent comments indicate that with 7 1/2 inch brakes you can't achieve lockup, so in an emergency situation.............?

[jdconnel]

I'd like to say I'm over thinking this, but in reality I have learned a ton.

I am speaking with a Dexter Application Engineer who is helping me run the numbers.
I have also download and read all their manuals several times.

I have also drawn up the configuration in AutoCAD to simulate what the ride height will look like, and how the axle pre-load will be affected (Yes. Mechanical Engineer here).

Going for "torsion arm is at or nearest the horizontal"
I believe I get that with the 10 degree down option It states a start angle of 10 deg will have a H = -0.1". This would raise my camper up 2.2". This would make it looks correct in my opinion. It would also leave the arm just slightly up from horizontal.

As for the brakes, I have been towing the unit with the 7.5's on it now with great success. Just finished 2500 miles, and no complains. I can say I tested them "once" when someone pulled out in front of me. I never felt like I couldn't stop in time. Good thought though. Hate to go through all this and find my brakes don't work

[jdconnel]

At this point, he is recommending a 3" bracket over the 1" high profile.
This would allow me to keep the 10 degree UP angle.

I see his concerns with having any negative angle on a axle with it's trailing arm forward.

[Johnny M]

I called Dexter to get a price on a new axle for my '71 Boelr 13'er and speced out with Ian G.'s recommendations it was $243. I called another Dexter location to speak with an engineer to get recommendations based on an estimated dry trailer weight of 1200 lbs and loaded at approx. 1350 to 1400. She said she could not for liability reasons give me her recommendations that it was up to me as to how I was "designing or engineering the trailer". I explained I was doing a restoration and all she could say is I need to get the trailer weighed and take the tongue weight and subtract it from the trailer weight to get the recommended axle weight and take into consideration the fully loaded weight... She did mention that on my thinner metal gauge frame whether it was square/rectangle, c channel or I beam type that their bolt on design could compromise the frame when torqued if not reinforced and that the bolt on bracket kit would probably be needed for my frame.

[stevebaz]

It is my understanding when your axle was built the square insert going into the axle tube was set with the points of the square running straight up and down. First level the frame. With a protractor measure the angle that will turn the insert back so its points are back to vertical. Remember your looking for the angle that moves your spindle back down to its original location. You can add that amount to the angle that the spindle arm currently sits to calculate what the factory angle was. You can see the square of the axle insert by its weld on the axle arm.