Ready for some backup for why you probably don't want to do bigger dropped shackle hangers on a trail vehicle? Here are some rough numbers for you. (without pictures because I have the new-guy limit still) I did a quick model of a Marlin Crawler front spring hanger for a SAS kit - probably looks like the basic design you'd use in the garage for a "home-grown" kit. Then I put in what I'm seeing for your hanger and we'll compare the results. When I can post more pictures, I'll add them to the post for you to check out.
I assumed that you're tweaking on this hanger with a quarter of the vehicle's weight and offset by the distance of the spring centerline to the center of the tire. That gives you the amount of torque that the spring hangers are going to see.
Assuming that the spring hangers each take an equal load, that gives you this amount of torque for each spring hanger:
1250lbs X 18in / 2hangers = 11,250 lb-in torque
The Marlin hanger develops about 20,000 psi at the spring bushing contact area on the inside of the (shown in the red areas on the picture that isn't yet uploaded) from your wheel. Steel can take 32,000 psi before it bends. The bent model looks like a part you'd take off of an old truck, which tells me that the model is ok for this rough analysis.
Then I add a piece of 2"x2" x 1/4" wall tubing on top of the hanger. Weld that onto your frame and then run the same loading analysis. Now the stresses jump up to 49,000 psi which means that something is going to break. Without the gussets, the break is going to happen at the weld between the top of the hanger and the bottom of your 2" tubing "spacer."
Now I add two 1/4" gussets to the hanger that you would weld to the frame. This makes the hanger stiffer, and decreases the stresses. Remember that the yield strength of steel is 32,000 psi (we're not worrying about the weld material strength of 60 or 70 ksi typical with stick welders because the hanger will break first anyways). This new model, with the gussets, develops stresses in the 42,000 psi range, way higher than the material yield strengh still.
I'd stick with some 2" hangers and spend the cash for some lift springs. Not only will your truck last longer, both on the trail and around town, but it'll be corrected for steering angles too.
Like I said at the beginning of the post, I'll attach pictures when my limit is raised for each of these studies to show where the bends/breaks will start. AND, if you have a different design in mind, describe it and I'll model that up for you...
- Brandon
