Two Design questions...

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REZARF

REZARF

Joined
Sep 8, 2003
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Location
Bozeman, MT
Two questions here and I would love your opinions.



1. I have recently built a rear tire carrier that I love. However, as I look into hooking up a scratch built trailer my pintle hook will not open without hitting my rear tire carrier "bumper.

Do you think that spacing the pintle out with a steel block, or heavy wall tubing and then bolting up the pintel would be safe?

I am thinking of 3x4" tubing with 1/4" wall with the sides boxed and bolted up to the crossmember and into the pintle, with seperate bolts.

The cross member is barely 3/16" thick. Will the forces increase that much to not consider this as a viable, safe option?

Billet steel is another option but hard to find in thick chunks.



2. Frame design. On the m101 can and m416 trailers the A-arm drawbars are both tied into the front shackle hanger mounts. Stregnth is increased in this design because the chasis can be tied into the leading edge of the trailer as well, just like the m416's. However, do you think the losses in strength would outweigh the gain in useable space of connecting the drawbars to the front corners of the trailer. By connecting the drawbars to the corners of the front edge of the trailer I can pick up nearly 1.5' of extra surface area to strap things down onto it. Strong welds are not the issue, either option will be properly TIG welded. What would you do and why?

Clear as mud? thanks for your opinions.

Rezarf <><
 
That really isn't what I am looking for but thanks for the link.

I am wanting to bolt the pintle to the crossmember, there is no receiver hitch involved.

Thanks-

Drew
 
Hi Drew,

I'll answer question 2 first. Well actually, you already answered this question in another thread.

https://forum.ih8mud.com/showthread.p...ighlight=m-416

The site you list in that thread (link below) has a trailer that has the A-frame draw bar extended for a carry basket.

http://www.blackburnimagery.com/Trailer_cost.html

The detailed pictorial slide show has exactly what you ask about. You click on the lower thumbnails to stop the slide show and jump around in the photos. You would lose a lot of strength by having the arms of the draw bar attached only at the corners of the frame because all of the stress would be directly at the welds. But, the builder in the slide show solves this by making the new arms of the draw bar longer so that they end up as wide as the trailer's frame. Notice that the original draw bar arms did not attach at the full width of the frame. That way you can still have the draw bar attached behind the front crossmember for strength while extending it forward for more room in front. This set up gives you the best of both, strength and more room.

Now question 1. Have you thought about lowering your pintle hitch. By using a 1/4" thick plate and a piece of 2"x2"x1/8" angle iron you could make a bracket like the one below. Use 3 or 4 bolts to attach the angle iron to the bottom of you rear crossmember. The pintle hitch attached to the 4 lower holes would give it the clearance you need. 2 bolts in the top of the plate and the 4 attaching the angle iron to the crossmember will help distribute the stress. Also, using a 1/8" thick backing plate inside the crossmember (where the hitch is mounted now) would help to strengthen it. If this backing is bent into an L shape and bolted through to the angle iron, it would be a whole lot stronger. This set up is similar to the bolt on receiver hitches for the FJ40.

If you don't want to lower the hitch. Then have a piece of 1/8" steel bent to make an L shaped backing plate to put inside the crossmember. Bolt it to the bottom lip of the crossmember before drilling the holes for the hitch. This will help distribute the added stress of spacing the hitch away from the crossmember.

Kevin
Pintle Hitch Bracket.JPG
 
Kevin-

Thanks man, I appreciate your feedback. Yeah, I don't desire to lower the mount any more, but if I do, I may scrap the whole thing and install a lock-and-roll in a reciever mount...

but for now, I am wondering the safe factor of doing this...
spacer.jpg
 
And here is my other delima, I have seen very reputable trailer builders use the second style draw arm setup, with plates that are welded under the frame that gusset and tie the draw arms into the frame, I can't see it being "that" much weaker. But I am no expert.

I am thinking of a triangular gusset on each end over lapping the frame, front crossmember, and the drawbars... this will increase usable space for sure.

Anyone?
draw-arms.jpg
 
REZARF said:
And here is my other delima, I have seen very reputable trailer builders use the second style draw arm setup, with plates that are welded under the frame that gusset and tie the draw arms into the frame, I can't see it being "that" much weaker. But I am no expert.

I am thinking of a triangular gusset on each end over lapping the frame, front crossmember, and the drawbars... this will increase usable space for sure.

Anyone?
Click to expand...

i'd go with the top drawing, looks much stronger
 
Drew,

Do you really need to space the pintle hitch out 4" from the crossmember to get clearance?

Kevin
 
Drew,

Go look carefully at the slide show at this site.

http://www.blackburnimagery.com/Trailer_cost.html

If you watch for the photos of the frame, I think that you will see that he extended the A-frame out at least the 1.5 feet that you said you'd gain in the first post. In fact, it looks like that guy got more like a 2 foot increase in tongue length by the way that he did it.

Here's an idea. Mock it up using 2x4s for the A-frame arms. That will show you just how much length you will gain.

Kevin
 
KY854RUN said:
Drew,

Do you really need to space the pintle hitch out 4" from the crossmember to get clearance?

Kevin
Click to expand...

Nope, but if 4" is safe... then anything less will only multiply the safety factor. This will go down the highway at speed and I will not compromise others safety.

As for the drawbars, I think you are right, that the option they used would be good. However they were using channel and I am using tubing... no exception.

Thanks!

Drew
 
KY854RUN said:
If you watch for the photos of the frame, I think that you will see that he extended the A-frame out at least the 1.5 feet that you said you'd gain in the first post. In fact, it looks like that guy got more like a 2 foot increase in tongue length by the way that he did it.

Here's an idea. Mock it up using 2x4s for the A-frame arms. That will show you just how much length you will gain.

Kevin
Click to expand...

Kevin- You are talking about the length of the drawbars... I am talking about the usable width of the rails the basket is sitting on. Picture a deck on top of the draw arms... I am wanting to gain space at the trailer edge not the overall length...

Clear as mud?
 
REZARF said:
Nope, but if 4" is safe... then anything less will only multiply the safety factor. This will go down the highway at speed and I will not compromise others safety.
Click to expand...

OK, I see what you want to do. You could use 1/8" wall box tubing and it would be strong enough. Just weld pieces of round tubing in where the bolts will go through so the box tubing isn't crushed. Make it wide enough so that it can be bolted to the inner bumperette mounting holes. This would help spread the stress over more area. Also, use an L shaped backing plate inside of the rear crossmember where the pintle hitch bolts go through. This should be strong enough. From your replies, I would guess that you will use grade 8 hardware to put this all together.

Kevin
 
REZARF said:
As for the drawbars, I think you are right, that the option they used would be good. However they were using channel and I am using tubing... no exception.
Click to expand...

REZARF said:
Kevin- You are talking about the length of the drawbars... I am talking about the usable width of the rails the basket is sitting on. Picture a deck on top of the draw arms... I am wanting to gain space at the trailer edge not the overall length...

Clear as mud?
Click to expand...

Now I see where you are trying to gain space.

Are you building a trailer frame from scratch or modifying one?

Kevin
 
Building from scratch and the idea is, if the drawbars are wider, I wont have to add a basket (more weight) and I can just make a mesh floor using the drawbars as sides to contain... whatever.

Thanks!

Drew
 
Drew,

Starting from scratch means that you can do whatever you want without having to deal with the short comings of what you have on hand.

You can build it like the lower design that you drew here.

attachment.php


Now to keep it strong. The side rails of the frame and the drawbar arms should start out as one straight piece of box tubing. Then make a V cut where the bend needs to be, but don't cut all the way through the tubing. You want to leave the outer wall of the tubing uncut. You will have to carefully calculate the angle of the V cut. Then bend the tubing and weld closed the cut. This will leave the outer wall as one continuous run of steel. then add the crossmembers and gussets and you will be in good shape.

Another way to do it would be, to have the side rails/drawbar arms bent to the correct angle. This is even stronger because there would not be any cut or weld to stress.

I can hardly wait to see the photos of your trailer build.

Kevin
 
Alright,

Here is the final decision, mostly inspired from a relook at Kurt's trailer and Wildyotes trailer...

A single 2.5" structural square tube with .25" wall. This will eliminate a bunch of fab work and geometry at the front end. It will also be the easiest to get really really square. There won't be more than 120lbs on the tongue at its HEAVIEST, so all the extra steel just isn't needed.

This also allows me to use a ball coupler on road, and then unpin and install a lunette ring for light trail work. I have a ball/pintle combo. In addition, the ability to do a 90 degree jackknife is possible with this setup.

The drawbar will be fully welded through the front and second crossmembers.

I will "gusset" the draw arm with 2" HREW tubing with .125" wall bent up on a bender, and the basket will sit on top of it. Clear is mud? The draw bar will be welded at each intersection of the crossmembers.

Any opinions? Flame away :D

Drew
drawbar.jpg
 
What do you think that the empty weight will be?

What is your projected gross weight?
 
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