Question about leaf springs on trailer

[maverick974]

Early last year I bought a 1984 Bayliner Trophy bass boat. Model # 1710. Nada lists this as a 17 footer but when measured with a tape, the boat is only 16 foot. Nada lists the weight as 1496 lbs. The boat is on the original trailer manufactured for Bayliner by Dixon Manufacturing in Butler TN. I tried calling them but apparently they either changed the phone number or they are no longer in business.
Late last year I hit a large pothole and flattened one of the springs just a little bit so I bought a new one and forgot about it. While fishing a few days ago I noticed that the side of the trailer with the new spring sits just a little lower than the other side. I also noticed that the shackles on the new spring are slanted towards the frong while the original shackles on the other side slant towards the rear. I'm guessing I bought the wrong spring.
The trailer was the same trailer made for several boats that Bayliner made back then.
Does anyone know the correct spring the manufacturer installed on these trailers? It's a double eye spring with 4 leafs.
Any help would be greatly appreciated.

 

[109jb]

Re: Question about leaf springs on trailer

Why not just buy another one like the one you bought last year and put it on the other side. You would then have matching springs. It shouldn't matter which direction the shackles lean as long as it is not severe.

 

[htv]

Re: Question about leaf springs on trailer

Why not just buy another one like the one you bought last year and put it on the other side. You would then have matching springs. It shouldn't matter which direction the shackles lean as long as it is not severe.

Sorry it matters a lot. If your shackle straps are slopped past perpendicular towards the rear of the trailer your spring can not and will not flex. For the spring to function the straps must slope towards the front of the trailer. Spring hanger centers on a single axle trailer should be about an inch longer than the bolt centers on the spring.

 

[109jb]

Re: Question about leaf springs on trailer

Sorry it matters a lot. If your shackle straps are slopped past perpendicular towards the rear of the trailer your spring can not and will not flex. For the spring to function the straps must slope towards the front of the trailer. Spring hanger centers on a single axle trailer should be about an inch longer than the bolt centers on the spring.

Which is why I said "as long as it is not severe.". Read the post....

 

[maverick974]

Re: Question about leaf springs on trailer

The problem is that the new spring doesn't have as much curve to it so it allows the trailer to sit too low. When I hit a bump the tire rubs the fender. If I hit a large enough pothole or if I would go up a curb too fast, the tire would hit the fender and be forced up into the hull of the boat which is exactlty what happened when I bent the original spring. Luckily it did little damage.
The fender doesn't sit outboard of the hull like most trailers, it sits under the boat slightly so I need to get the trailer back to it's original position.
The shackles on the original spring tilt slightly towards the rear. Hardly at all but the new spring must be shorter as the shackles tilt quite a bit towards the front. I measured both of them and it appears that I bought a spring that is 1/2 inch to an inch shorter than the original. Yes I measured them unsprung.

 

[htv]

Re: Question about leaf springs on trailer

Which is why I said "as long as it is not severe.". Read the post....

I read the post. If the rear spring bolt is past the hanger bolt towards the rear, the spring will not flex. It is like you lifting yourself up by your boot straps. Physically impossible.

 

[109jb]

Re: Question about leaf springs on trailer

I read the post. If the rear spring bolt is past the hanger bolt towards the rear, the spring will not flex. It is like you lifting yourself up by your boot straps. Physically impossible.

That is ONLY true when the spring bolt is directly behind the hanger bolt. As in the front eye bolt, the rear hanger bolt and the shackle bolt all form a line. As long as the hanger still has room to swing it doesn't matter.

 

[htv]

Re: Question about leaf springs on trailer

That is ONLY true when the spring bolt is directly behind the hanger bolt. As in the front eye bolt, the rear hanger bolt and the shackle bolt all form a line. As long as the hanger still has room to swing it doesn't matter.

OK, lets try this. We all agree that for a spring to flex the center to center eye dimension has to increase. The front eye is in a stationary position, so any change in spring length comes from the back of the spring. Since the front is mounted in position for that spring to flex the rear eye must go downwards which happens naturally when the shackle is towards the front of the trailer. Now, once you have gone past the fulcrum point, (shackle perpendicular to hanger bolt) for the spring to flex the rear eye still needs to go in a downward motion but it can't because the force is forcing the the spring end up.
You might find it helpful to just draw both configurations down on a piece of paper and imagine in what direction that rear spring eye must travel to flex.

 

[bruceb58]

Re: Question about leaf springs on trailer

Post a picture of both springs so we can actually see what you are talking about here.

 

[109jb]

Re: Question about leaf springs on trailer

HTV, which drawing below is how you say the spring won't flex?? I have labeled them configuration 1 and configuration 2.

 

[Silvertip]

Re: Question about leaf springs on trailer

It seems a few experts have spoken but they have spoken false information. Spring shackles on a leaf spring setup face slsightly rearward and they face that way for a reason. It's called REBOUND. Before getting into this though, the actual angle of the shackles is calculated based on the weight of the empty trailer. If the shackles faced forward at all, it is possible that on a pothole type of bump where the wheel falls into a depression, the spring now carries unsprung weight which is the axle, wheels and tires. This weight pulling down on the spring causes it to shorten. No big deal you say! Well it is a big deal because the shackle can move so far that it jams and breaks things. The following picture came from a spring and trailer manufacturer so I think they know what they are talking about. Compression is the situation where the trailer hits a bump (upward) and the initial response of the suspension is for the wheels and axle to be sharply pushed upward. That action results in the spring being compressed so its length increases because it is an arc to start with. As we learned in geometry, flatten an arc and it gets longer. So the spring shackle allows that rearward movement. Now look carefully at the picture. Note that in the unloaded position (as though the frame was supported by jacks and wheels were hanging down) the shackles are very slightly angled rearward. When the frame weight is applied to the suspension the shackles move farther rearward in arc defined by the length of the shackle. If at any point in the suspension travel the shackles face forward, this change in the spring arc coupled with the forward facing shackles will cause suspension bind. In an unloaded situation (as in severe rebound) this design cannot jam. Have a look at a pickup or any truck or stop at a boat dealer and have a peek at some leaf spring setups. You will see the shackles all face rearward - some more, some less. Just for the record, I've built trailers ranging from six place snowmobile haulers to light duty utility and I assure you, spring shackles do not face forward unless the spring is too short or the rear shackle mount is installed wrong.

 

[htv]

Re: Question about leaf springs on trailer

HTV, which drawing below is how you say the spring won't flex?? I have labeled them configuration 1 and configuration 2.

#2. Silvertip did a better job of explaining (good to see another expert). When I say the shackle straps should point to the front is with no load. What I was trying to explain is that the spring hanger centers has to be more than the spring centers. Silvertip laid out his credentials so now I don't feel so bad laying out mine, and I'm not a spammer. I was raised in a family all involved in trailer manufacturing and I built trailers as young as 13 years old. I have been involved in building, selling, repairing and selling trailer parts for over 40 years and am still selling complete line of parts currently. I may be a cadet to this forum, but am a seasoned(maybe to seasoned) deck hand regarding trailers. I'm just here to be of service and try not to **** on anyone's parade.

 

[karlow1]

Re: Question about leaf springs on trailer

As if that is not clear enough. You need two new springs, that way they will match. They need to be longer than the last one you bought. when the trailers is unloaded the shackles should be vertical or slightly to the rear. When loaded, the shackles must lean to the rear. Anything else is unsafe!

 

[maverick974]

Re: Question about leaf springs on trailer

Ok. Here is what I did. I took the boat and trailer to a business called Six Robles which specializes in trailer parts, axles, springs, lights, etc. They don't actually build trailers as far as I know but the carry most everything for trailers.
I had the guy look at the trailer and he said that the original spring has flattened out over time and that's why the shackles are leaning towards the rear. He also pointed out that the hanger on the side that is low is slightly bent up vertically. He said the spring is correct. He sold me a matching spring for the other side. He also pointed out that I installed the spring backwards. The clip that wraps the leafs that is imprinted with the specs is supposed to go in front of the axle. I'll fix that on Sunday and install the new spring as well.
Here are the measurements. The distance between the hangers is 25 1/2 inches. He sold me a spring that is 25 1/4 inches long with a capacity of 1750 pounds. So the spring (with no load) is 1/4 inch shorter than the hangers. Once the spring is installed and under load, the shackles are almost vertical but leaning slightly towards the front.
Is this correct?

 

[Silvertip]

Re: Question about leaf springs on trailer

If you are talking about the top of the shackle pointing to the front, yes, that's correct. If you are talking about the bottom of the shackle facing forward, no, that is not correct. Rebound (unloading) in that case would shorten the spring causing the possibility of binding due to a very sharp angle of the shackles. Here are a couple more pictures of proper spring installation.

This is the front leaf spring on a Ford F250. The bottom of the shackle clearly extends rearward.

Here is a design drawing showing details for both slider and shackle installation.

There is a trick in racing where rear spring shackle adjustment (forward at the bottom) causes the chassis to "jack" or rise on spring deflection. But that's not the way it's done on trailers. Rearward softens the ride due to the reduction of spring rate.

 

[maverick974]

Re: Question about leaf springs on trailer

I have several small trailers and a truck. All of them have leaf springs and on all of them, the leafs are leaning towards the rear. In other words, the springs are slightly longer than the distance between the two hangers. The hangers are 25 1/2 inches so I'm assuming that I'll need 26 inch springs.
Does that sound correct to you folks?
Six Robles sold me a 25 1/4 inch spring.
What sounds right to you?

 

[Floatsum]

Re: Question about leaf springs on trailer

If you are talking about the top of the shackle pointing to the front, yes, that's correct. If you are talking about the bottom of the shackle facing forward, no, that is not correct. Rebound (unloading) in that case would shorten the spring causing the possibility of binding due to a very sharp angle of the shackles. Here are a coupl...

I kept reading this post and thinking WTF?
To me the anchored to chassis side shouldbe inside of the spring end under load.
Reading the above I couldn't for the life of me figure out what was being meant.
Now I'll agree.

 

[maverick974]

Re: Question about leaf springs on trailer

Well, I think the consensus is for longer springs and you guys know much more about this than I do.
I'm going to purchase 2 springs 26 inches long. I'll install them early next week. I'll post here and let you know how it goes.
Thanks for all the imput. All of you were very helpful and I greatly appreciate it.

 

[htv]

Re: Question about leaf springs on trailer

I called a trailer manufacturing company and wholesale parts distributor with 6 distribution centers and in business for 45 years. In their manufacturing and parts sales they set spring hanger centers 1/2" longer than center eye to eye than the spring. I asked how long has this been their standard and replied, "about 45 years." This is the way I have done it also for about 45 years.

 

[Silvertip]

Re: Question about leaf springs on trailer

Think a little bit folks! Spring hangers are set a tad longer than the length of the spring because this dimension is critical to the UNLOADED vs loaded configuration. When the weight of the trailer sits on the springs the spring deflects, it gets longer, and the bottom end of the shackles will now point to the rear. Look at the design drawing I just posted. Does that drawing not say the shackles should sit 90 degrees or less from the centerline of the two spring eyes? 90 degrees or less does not point the shackles forward, it points them rearward. If they pointed forward that angle would be greater than 90 degrees. But if you are geometrically challenged, I can only suggest you go out and look at some trailers. Please take pictures of any you find with the shackles facing forward. You will find some but it involves another design that essentially flips the rear spring hangers. But you won't find them on a trailer.