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Old 06-08-2010, 12:32 PM
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Watt's link on Front axle?

Hey there folks,

I'm working on a 50' chev pickup and need some advice. I took off the front leafs and made radius arms to attach the front axle to the frame. They attach via 3/4 heims to the rear leaf spring mount and bolt onto the front axle. I mounted airbags on the outside of the frame as well. At the same time I did a cross-steer conversion in front of the axle. The radius arms are about 18" long

What I am worried about is that even though everything is built sturdy I still have two arms sticking out front with the axle bolted on and am concerned about side to side strength. For whatever reason I thought I would have enough side to side play for a panhard bar. I don't....the panhard just locks it up. So I thought about a watt's link. I think I have enough room. Is this a good idea or am I leading myself down a path of destruction? Has anybody heard of this being done before? Do I need the link at all? Any help would be great!

Thanks!

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Old 06-08-2010, 04:52 PM
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you MUST have something to control lateral movement.
A watts link will work fine, from a geometry standpoint it is superior anyway
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Old 06-08-2010, 05:26 PM
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You are right. I think I would be scared to death without control of lateral movement. Thanks for the input!
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Old 06-08-2010, 07:06 PM
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The only thing I'd be concerned about is that with a watts link on a front axle with cross steer is that now the axle will travel up and down without any side movement, but the cross steer drag link still travels in an arc..So you may see some small amount of bumpsteer as the drag link travels in it's arc..

It's true that a watts link is superior, on a live rear axle, but the wheels are fixed in a straight ahead position. On an axle with kingpins, and a link from the steering arm to the pitman arm on the frame, you'd be building in bumpsteer. You probably wouldn't notice it too much, if the suspension travel was 2 or 3 inches. (My 73 blazer with side steer has about 1/8 turn at the steering wheel when I hit a good bump...I just let it turn)

later, mikey
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Old 06-08-2010, 08:01 PM
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10-4 on bumpsteer geometry (face palms), but as mike said it would me minimal
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Old 06-08-2010, 09:11 PM
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I really appreciate the responses. I fully agree about the bumpsteer. About ten years ago I put a power steering conversion kit on the truck that place a 1/2 ton chevy box in front of the axle. The power was nice, but the bumpsteer was crazy. If it is less than it was then I will be ok. I designed the setup to run at 4" travel to the frame. Obviously I don't want to hit the frame so I am counting on about 3" of travel. As far as the bumpsteer goes I guess I will find out how it feels. I just don't want the front axle to rip out going around a corner because I didn't give it enough support. I have been known to run this old girl like a three dollar rented mule. Thanks again for the input everyone. I've found that there is nothing more valuable in rodding than listening to others who've been there already.
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Old 06-09-2010, 04:40 PM
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Ok guys...I have another idea. The reason the old chevy trucks with trailing arms worked is that they had rubber bushings in the ends so it would flex with the trailing arms. That way the panhard bar wouldn't lock up the rear suspension. If I traded out the heims for rod ends with rubber bushings would it give me enough flex to use the panhard on the front end and at the same time reducing bumpsteer? What do you guys think? Thanks in advance.
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Old 06-09-2010, 04:50 PM
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I'd do the rubber bushings. It'll be quiter too, and won't get loose like heims.

Later, mikey
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Old 06-10-2010, 12:06 PM
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I didn't read every word so sorry if this has been mentioned.

When I read that a panhard bar is "binding" that tells me you set it up TO bind. The only reason it would bind is it is on a different plane than the axle is moving. If you have cross steering and it isn't on the EXACT same plane/arch as the panhard, you WILL have binding.

I am thinking that the panhard bar is the one to go with and you just need to set it up properly.

Brian
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Old 06-10-2010, 12:21 PM
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the reason it is binding has nothing to do with the steering. The steering is not connected right now. It is binding because the I have two radius arms connected to the axle and that is very solid. There is absolutely no side to side movement at all. With no side to side movement the panhard will only lock it into place, therefore that is why I need either rubber mounts, instead of heims, to create some play or put in a Watt's link to make up for the fact that there is no horizontal movement since the Watt's link only allows vertical movement. You are right. I set it up that way and it is incorrect. So my two options are: create some side to side movement so the panhard bar will have room to move or a Watt's link. I think I'm going with the rubber mounts.
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Old 06-10-2010, 02:13 PM
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You might want to re-evaluate the way you mounted the trailing arms to the 50 chevy axle..if you solidly mounted the trailing arms to the leaf spring pads on the axle, you are going to wind up with sheared bolts..I'd be thinking about using some kind of rubber or urethane isolators between the 2 to allow a little twist or flex at the connection..

Traditional batwings allow some movement, so do wishbones...

Just something to think about..

later, mikey
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Old 06-10-2010, 02:51 PM
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The trailing arms attach via a "C" that goes on top and below the axle. the two back bolts blot to the top plate and the two front go all the way down and clamp the top and bottom together with spacers so they don't clamp too far. Each side has 4 1/2" bolts holding the axle to the arm. Do you think it would shear 4 1/2" grade 8 bolts? I guess I am trying to imagine the force from which direction that would shear them off. My wishbone on my 26 ford with a 40 ford axle seems like it would have a better chance of shearing. One bolt per side. You are right that it does allow some side to side movement where my 50' doesn't, but other than that the vertical movement is the same. Are you talking about bolts shearing due to the panhard bar putting pressure on the front end? I was hoping changing the heims out for rubber bushed rod ends was going to allow some movement. The last couple days I've been thinking about 2" rubber bushings in the rod end with the same 3/4" bolt holding it to the frame. I should take some pictures so you guys can see how it looks now
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Old 06-11-2010, 07:31 AM
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Here are some pics so everybody can have a better idea of what I'm talking about
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Old 06-11-2010, 08:09 AM
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If it was me , given that setup, I'd do a diagonal brace from the left rear trailing arm mount to the right front trailing arm where it attaches to the axle...That setup is about as stiff as can be, and with the way you attached the trailing arms to the axle it's now it's own swaybar...The good news is that I beam axles do flex in the middle, by design...The questionable part is that as the front axle flexes, where your trailing arms mount to the axle, will want to rotate slightly...but with the small amount of travel you have, it might be alright.

Think of it being just like ladderbars on the rear, but with much shorter ladder bars, no flexibility at the point where the bar meets the axle, and with much more widely spaced attachment points...Ladder bars are designed to twist slightly, and they allow some lateral flex at the batwings...that's how you keep them from breaking.

I doubt that you will break the bolts, but I'd watch the welds where the square tube attaches to the C bracket, as well as the bushings and brackets at the frame. Although, you put enough gussets there that I think it'll be ok...

JMO.

Later, mikey
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Old 06-11-2010, 11:22 AM
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Thanks Mikey, I like the diagonal idea. That would mean I don't have to change much, just put in a new bar. Believe me...I will be keeping an eye on the welds. Thanks!
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