Pikemans M101 A2 slow Expo/ Base camp trailer build.

[Pikeman]

Ok a few questions after reading another build where everyone was thrashing( okay strongly criticising) a guy for his tongue design. I purchased a military M101 A2 trailer and sold the original tongue and axle. What is left is the rectangular frame that is made of channel that is 4" tall with 1.25" lips and I believe 3/16" thickness dimensions are 45" wide and 96" long with cross members every 2'. The box is like a pick up bed that bolts to the frame. I will try to take a picture and then do my best to draw in my tongue design in later. For now here is my plan if I can write it out.

material would be matching channel to frame material and 7' of receiver tube. The receiver tube will run through the front cross member and butt against the second cross member. I will run 1/4" plate gusset where it goes through current frame channel and also where it butts to second cross member. It will have 2' between frame members and 5' of tongue length in front of trailer. The channel will be from front frame member to 10" of end of receiver tube or 50" in front of trailer frame. I feel this will be plenty strong for a 2000-2500lb trailer.

 

[TRegasaurus]

Not thrashing, rather it was constructive criticism. There's a difference.
He had a design problem that needed to be pointed out and those who said so also pointed to a possible solution.
This forum wouldn't be much good if all we did was cheer on the sidelines while someone designs in a weakness.

 

[Pikeman]

Ok it was strong criticism and not a thrashing, and if I was offended or didnt think I could get helpful input I wouldnt have asked. Here is what my frame looks like, still havn't figured out how to draw on it. Maybe I will sketch it out and upload that tomorrow.

This is the back cross member but the front is the same. Distance in between the D ring mounts is 36" and the new A frame channel will be up against them.

So the A portion will be 35-36" wide at base and meet the receiver tube at 50" in front of cross member. The receiver tube will extend 10" beyond A frame.

 

[JeepDork]

More info needed

Your tongue needs 75000 lb-in at 5ft and 2500lbs. Vertical Capacity of 2.5" .250 receiver tube= 45400 @ 5ft plus the two pieces from frame to tongue. We can't figure that out because we don't have enough info (the length of the two "A" arms). If you were to us just the single square tube then as you can see it wouldn't be enough. More info please such as the length of the sides of the tongue and the distance from the junction of the 3 pieces and the end of the tongue.

Your quick and typed my answer before I asked it, damn your good!

 

[Pikeman]

Ok here is a very rough idea of the concept. I really suck with computers. Remember this is going through the crossmembers.

 

[JeepDork]

OK from what I can tell L1 is 12500 you have 45400 OK there, L2 is rated at 61800 plus the 45400 total is 107200 and your requirement is 75000 for L2. Now the chart I have doesn't allow for the 1.5" x 4" 3/16 channel you are using. I used 2x3x3/16 as the closest thing. I think yours would be even stronger. The strength in channel comes more in the vertical than the horizontal. So in a nut shell 12500 needed you have 45400 and 75000 needed and you have at least 107200. Here is the catch these are all measurements based on mounting the a frame UNDER the front frame rail no to the front frame rail. This was based on 2500 lbs too. I would use a doubler as you mentioned on the vertical side of the frame where the receiver tube goes through. I can't see you ever having a problem with the set up you'd explained though.

 

[JeepDork]

The gusset the way you have it isn't needed. That is placed for side load on the center tube which will be fine because it is mounted through the frame tube and the "A" arms supporting the center receiver. You would be better off to lay it flat against the front of the frame tube to reinforce it there. That becomes (as others have said) a hinge point. That is why most build charts place the tongue UNDER the frame not into it.

 

[Pikeman]

The gusset the way you have it isn't needed. That is placed for side load on the center tube which will be fine because it is mounted through the frame tube and the "A" arms supporting the center receiver. You would be better off to lay it flat against the front of the frame tube to reinforce it there. That becomes (as others have said) a hinge point. That is why most build charts place the tongue UNDER the frame not into it.

ok so if I place a piece of 1/4" Angle or plate on the face of the cross member that the receiver runs through it should add to the strength. However because the worry of hinge is why I want to run it to the second cross member and gusset it.

 

[bob]

Are you cutting into the frame to run the main tube(reciever) through, or are you laying it on the bottom.

 

[Mark Harley]

Why the change? The hitch mount will be 4" higher now than original.
I would cut a tight fit hole in the front cross member, extend the tube back to the second cross member
and triangulate the stiffeners from the inside of the lift hoops.

I left mine original and used a channel for adjustment. switching between a lunette and 2" coupler.
Keep us posted on the build.

 

[Pikeman]

Bob,
Yes I will be cutting a hole through the frame to run the receiver tube. The frame is 4" and the receiver is only 2.5"

Mark,
That is my plan is to run it back to the second cross member and run a gusset there and also a 1/4" doubler plate where it goes through the front frame. The sides will be where you mentioned. Also on the original the Lunette was in-line with the frame as the surge brake sits above the A-frame.


Reason for the change is I will be running the Max Coupler and needed receiver tube for that and also wanted the additional clearance by moving it up. It will still sit level with my tow vehicle.

 

[Pikeman]

The reason I am asking is I want to verify my logic. I know if I was face welding to the front cross memeber only that becomes a hinge and weakest method. Now my thoughts on going through the frame versus under.

Under frame- only have 2.5" of weld in two spots(front cross member, second cross member), then 1" of weld in 4 spots(each side of A on front cross member and side)

Through frame- 10" of weld in two spots( were it goes through front cross member and where it butts to the 2nd cross member), 6" {12 if you consider welding all the way around the channel}of weld in two spots where each side of the A welds to the front of trailer. Not to mention any gussets like double plating the front frame which also spreads the load wider and adding a slanted gusset on second cross member that captures the sides of the receiver tube as well.

 

[bob]

Going through the frame, or when originally building going through the frame is always the strongest. Never weld to the front cross member because as stated above it becomes a hinge area and will eventurally break due to weight and bounce.

With what your plan is, the frame should be bullet proof.

 

[JeepDork]

Going through the frame is NOT always strongest. Going under is stronger for weight carrying capacity. It all depends on which materials are being used where. For your application going through is plenty strong enough, but going under is going to give more tongue capacity. Remember it's not just the load amount but at which angle this load is applied. For weight and bounce as bob wrote under would be stronger. If you look at most large manufactures of heavy haul trailers the tongue usually extends under the front and down the sides of the frame. This gives you full strength of the frame rail and the tongue rail. I agree with Bob about your plan, the frame will be fine.

http://bigtextrailers.com/trailers/equipment_heavy.html

 

[bob]

Going under the frame gives you the double strength of the two pieces, but it is not as strong in twisting situation. I think it ends up near 2/3 less welded surface. It is also much easier than integrating it into the triangle. Saves Big Tex money and time. It has been proven over the years to be a totally safe way to build trailer frames and many companines build frames that way. Whether it be desgin or eye appeal I am not certain. I actually built my new trailer this way. Wanted to see how much quicker it was and if it would do the job. After using it and checking the welds I am sure it is just fine. I still like the integrated look better, but doing each and every frame it sure cuts down the time. What normally would take a good three hours to cut, align on the jig, clamp and weld from one side to the other, takes less than an hour to stick, align and weld.