Building a dolly, odd question

YungICY · Dec 13, 2015

Hey guys, I'm looking to build a dolly to tow around my prerunner and I have an odd question. My father in law has a dolly/trailer for his buggy that someone built for him and the axle on it is actually just a couple of kingpin beams welded in place and to a tube in between them.

Now I have a couple sets of forged ranger beams lay in around that I can do the same thing with.

My question is, I noticed on my father in laws, whoever built his built the king pins to have caster in them. Is that necessary? If so I would just imagine 4 or 5 degrees would be fine. If someone can confirm this for me I'd appreciate it.

Thanks in advance.

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Captain Ledd · Dec 13, 2015

You mean as a self steering setup? Or to just use the beams and weld them so they're straight?

YungICY · Dec 13, 2015

I'll just weld them so they're fixed straight. I'm just curious if the caster is needed. Part of me says yes and the other part of me says it shouldn't matter.

I guess now that I've vocalized it it would make the most sense to just set em at like 4 or 5 degrees and call it a day.

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don4331 · Dec 13, 2015

Caster provide a degree of self-centering for the steering; making car easier to drive.

But is you weld the joint solid; you effectively make the caster 0* as the wheels can no longer pivot to 'force' the wheel back to straight.

So, pick whatever angle you want.

I'm curious on what you are going for suspension/how you secure the buggy/pre-runner to the dolly.

Don

YungICY · Dec 14, 2015

That makes sense. That was kind of the inner dialogue I had going on in my head lol.

As far as suspension I'm not going to run any.

For securing it I'm going to use some heavy duty tire style ratchet straps. Then I'll probably put a chain ratchet I little more forward on the tongue that I can tighten down and make sure it doesnt fall off the back in the event of a strap failure.

The only aspect I haven't worked out in my head yet is a pivoting platform.

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RonD · Dec 14, 2015

Yes, castor is needed because there is another set of wheels on the ground behind the dolly, towed vehicle's front or rear wheels depending on how you are towing it.
It makes it more stable.

Captain Ledd · Dec 15, 2015

But if it's not steering, there still wouldn't be any caster. Lots of tow dollies have straight axles or drop axles, and a straight axle would have no caster no matter which way you twisted it (assuming it doesn't have the pre-bent tube to compensate for weight), and any caster on a drop axle would just add stress and torsion on the spring, like axle wrap.

Caster is mainly there for it's ability of returning to center after turning. It helps keep the wheels in a straight line when they can move, like a bias toward going straight. If the wheels are fixed and cant move, there's no need for it because they're going to go in whatever direction they're pointing.

pjtoledo · Dec 15, 2015

YungICY said:
That makes sense. That was kind of the inner dialogue I had going on in my head lol.

As far as suspension I'm not going to run any.

For securing it I'm going to use some heavy duty tire style ratchet straps. Then I'll probably put a chain ratchet I little more forward on the tongue that I can tighten down and make sure it doesnt fall off the back in the event of a strap failure.

The only aspect I haven't worked out in my head yet is a pivoting platform.

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put lots of thought into a pivot system. if done poorly you have the recipe for jack-knifing any time the brakes are applied.

Perry

YungICY · Dec 15, 2015

pjtoledo said:
put lots of thought into a pivot system. if done poorly you have the recipe for jack-knifing any time the brakes are applied.

Perry

Thanks for the heads up Perry.

How important is it to have a pivoting platform?

And just for additional info concerning it, I plan on Lincoln locking the diff on my prerunner at some point. I don't know if that plays a big role for that or not but it seems like it would.

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Captain Ledd · Dec 16, 2015

It's VERY important to have a pivoting platform, because that's how it turns. the only other option is to have the dolly wheels turn to follow the tow vehicle, which is complicated and probably still won't work as well as a pivot.

If you have neither you will only go straight, and probably damage suspension components on your vehicle or damage the dolly, likely both, irreparably.

pjtoledo · Dec 18, 2015

stop by a Uhaul and look at their setup. I have seen dollies that do not pivot, never used one of those.
the problem with something that pivots easily is during a fast stop the momentum of the towed car needs to go someplace. with a pivot at each end, at the hitch ball and under the car, there is nothing to keep it straight and it can go sideways real quick.

Patriot1776 · Dec 21, 2015

Those dollys at uhaul seem to all have about 30 degrees of pivot in them. I assume that would prevent the jackknifing effect for the most part. The couple times I have used them they seemed to tow extremely nice. I would just keep an eye out for an old uhaul dolly to buy. Or get a full on trailer.

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pjtoledo · Dec 21, 2015

Patriot1776 said:
Those dollys at uhaul seem to all have about 30 degrees of pivot in them. I assume that would prevent the jackknifing effect for the most part. The couple times I have used them they seemed to tow extremely nice. I would just keep an eye out for an old uhaul dolly to buy. Or get a full on trailer.

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I wonder if they are spring loaded to keep them on center?
I'll have to look some day.

Perry

adsm08 · Dec 21, 2015

The u-haul dollies can jack-knife. I have the busted up 7-pin to prove it.

85_Ranger4x4 · Jan 1, 2016

Captain Ledd said:
If you have neither you will only go straight, and probably damage suspension components on your vehicle or damage the dolly, likely both, irreparably.

If the dolly he is copying doesn't have an issue with that I don't think the one he is building would either...

For caster, it is going to vary in the real world as the towing vehicle and towed vehicle go over bumps the tongue goes up and down so it won't be an exact thing anyway. Get it all set perfect on your truck and as your springs age and as you have cargo in the back of your truck it will vary. Then you get a new truck and it is all "out of whack".

Building a dolly, odd question

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