Fish Plates (DollyTrolly?)

[SuiteSuccess]

Dolly or others,

I re-read the previous thread on StopSaddles ramp failure at the hinge and the use of “fish plates” to strengthen the hinge area was discussed.  I have an idea of their use on railroad tracks but could someone post pics or an understandable discussion how to use them on the smart ramps and still allow flexing at the hinge?

[HERO Maker]

Carl, I missed the 'fish plate" comment, but for the ramp I believe they are meaning a simple piece of angle iron placed between the top of the junction of the to two ramps.  It will open up that hinge just a bit and may allow more height to clear the bottom of the car as it breaks over the side of the bed.

[Star Dreamer]

The fishplate would be a plate on each side of each ramp that bolts to both pieces and spans the joint. Once attached the ramps will not hinge, but if configured properly you could keep one side attached and unbolt the other side to still allow ramps to be hinged for storage. However the one ramp will now be longer by 1/2 the length of the fishplate. In that is an issue just remove the fishplate. You could use wing nuts to attach the plate for easy removal.

Dave

[SuiteSuccess]

22 minutes ago, Star Dreamer said:

The fishplate would be a plate on each side of each ramp that bolts to both pieces and spans the joint. Once attached the ramps will not hinge, but if configured properly you could keep one side attached and unbolt the other side to still allow ramps to be hinged for storage. However the one ramp will now be longer by 1/2 the length of the fishplate. In that is an issue just remove the fishplate. You could use wing nuts to attach the plate for easy removal.

Dave

Thanks Dave.

[Dollytrolley]

On 11/20/2017 at 5:52 AM, SuiteSuccess said:

Dolly or others,

I re-read the previous thread on StopSaddles ramp failure at the hinge and the use of “fish plates” to strengthen the hinge area was discussed.  I have an idea of their use on railroad tracks but could someone post pics or an understandable discussion how to use them on the smart ramps and still allow flexing at the hinge?

S. S. 

Sorry I was asleep at the switch......and missed your post.

Sometime ago I posted a comment about installing doubler-plates ("fish-plates") at the joints on folding ramp hinge points so the hinge no longer carries the beam loads at the hinge pins.

Being a geezer I do not recall the details of my fish-plate post but it was likely a couple 36 inch long 2 x 2 x 3/16 angle iron centered at the hinge point so that 18 inches of angle is placed on each beam side of each ramp and then two holes would be match drilled in each of the two end of the fish plates and the ramp beams.

Here is the point that requires some thought and that is what is known as "Edge-Margin"..........the fish plate bolts should be large enough to withstand the double shear of the beam load but no so large that the holes do NOT exceed TWO times the hole diameter from EACH edge of the beam as a rule of thumb. 

Many consumer ramps are fabricated from extruded sections that have limited hole loading so it is best to inspect the holes often for deformation.

Fish plates are a low-tech way to relieve hinge loads but the cost is that it takes a bit of time to install the fish plates prior to ramp use.

 

Drive on............(Don't become........unhinged)

[SuiteSuccess]

10 hours ago, Dollytrolley said:

S. S. 

Sorry I was asleep at the switch......and missed your post.

Sometime ago I posted a comment about installing doubler-plates ("fish-plates") at the joints on folding ramp hinge points so the hinge no longer carries the beam loads at the hinge pins.

Being a geezer I do not recall the details of my fish-plate post but it was likely a couple 36 inch long 2 x 2 x 3/16 angle iron centered at the hinge point so that 18 inches of angle is placed on each beam side of each ramp and then two holes would be match drilled in each of the two end of the fish plates and the ramp beams.

Here is the point that requires some thought and that is what is known as "Edge-Margin"..........the fish plate bolts should be large enough to withstand the double shear of the beam load but no so large that the holes do NOT exceed TWO times the hole diameter from EACH edge of the beam as a rule of thumb. 

Many consumer ramps are fabricated from extruded sections that have limited hole loading so it is best to inspect the holes often for deformation.

Fish plates are a low-tech way to relieve hinge loads but the cost is that it takes a bit of time to install the fish plates prior to ramp use.

 

Drive on............(Don't become........unhinged)

So Dolly are you saying that the holes are a little larger than the bolt to allow the hinge to flex slightly under load but become rigid at a certain amount of flex?  Or is the hinge rigidly fixed at the outset?

[GeorgiaHybrid]

Carl,

He is talking about the edge distance on the holes you add to the ramps. He is saying you want to have double the size of the bolt for an edge distance to the closest edge of the material. In other words, if you use a 3/8" bolt, the nearest edge of the material should be 15/16 from the center of the bolt. (3/8x2=3/4 + 1/2 of the bolt dia which is 3/16 giving you 15/16). That is the conservative approach looking at his suggestion or you can look at just making it double the size of the bolt from the centerline which would be 3/4" for a 3/8" bolt (don't know which way Dolly was speaking of) If it was steel we were talking about you can go less but aluminum is a little softer material.

It will take a little work to decide the size of the bolt that you can use in your ramps. Most likely, you will wind up with a 5/16 or 3/8 bolt as your maximum. The longer the plate, the better it will resist the load. In his example above, Dolly would more than likely put a bolt about 16" from the center and at 8" from the center on each side.

Not positive about that spacing with Dolly though as everyone will have their own ideas on loading but that is the general principal behind adding a fish plate or flitch plate to strengthen a connection.

[SuiteSuccess]

Thanks Dave.  After re-reading Dolly’s post I get it.  So if one were to add the plates, the ramps would not flex down at the hinge while driving or winching the smart but would remain rigid, am I correct?  So top half would have less break over angle.  Sorry, I just want to be sure I understand.  I’m not planning on adding any plates as no one is in the car up or down, so if the ramps break only car will be hurt.

[GeorgiaHybrid]

Carl,

It would eliminate the flex in the hinge but to help with the break over angle, I made a couple of mini ramps using an 20" section of 2x10 and a 10" section. Screwed the two together and lift the bottom of the ramp and slide them under it. Now the car goes down the ramp, hits the 3" high section of wood ramp, onto the 1 1/2" high section of ramp and then the ground. If needed, I can also dump the rear suspension to help with the clearance as our smart car has the lowered sport suspension.

[Dollytrolley]

9 hours ago, GeorgiaHybrid said:

Carl,

He is talking about the edge distance on the holes you add to the ramps. He is saying you want to have double the size of the bolt for an edge distance to the closest edge of the material. In other words, if you use a 3/8" bolt, the nearest edge of the material should be 15/16 from the center of the bolt. (3/8x2=3/4 + 1/2 of the bolt dia which is 3/16 giving you 15/16). That is the conservative approach looking at his suggestion or you can look at just making it double the size of the bolt from the centerline which would be 3/4" for a 3/8" bolt (don't know which way Dolly was speaking of) If it was steel we were talking about you can go less but aluminum is a little softer material.

It will take a little work to decide the size of the bolt that you can use in your ramps. Most likely, you will wind up with a 5/16 or 3/8 bolt as your maximum. The longer the plate, the better it will resist the load. In his example above, Dolly would more than likely put a bolt about 16" from the center and at 8" from the center on each side.

Not positive about that spacing with Dolly though as everyone will have their own ideas on loading but that is the general principal behind adding a fish plate or flitch plate to strengthen a connection.

Very nice explanation of the concept G. H........

The reason I suggested the TWO Dia edge-margin is indeed soft extruded alum used in many of the fabricated light weight ramps tend to become somewhat upset in  the bolt holes when loaded to the larger loads so it is best to keep some margin to spare so that the pin-joint at the end of the flitch-plate does not become the next point of failure. 

The concept here is not to upgrade the ramp capacity but to help bridge the loads in such a manner to assist the hinge loading.

As G. H. has wisely pointed out..... too much bolt diameter can actually be too much of a good thing that can become a bad thing IF the bolt holes become so large in the ramp beam web that the hole(s) weaken the beam more than the plates reinforce the beam.......

Seems we might be approaching the need to get Henry jazzed up with the FEA gizmo or..........maybe I might need to see if I can pry the old slide rule out from under the pillow of my pine-box..........

 

Drive on..........(Fish my.....plates)

 

 

[ALLOY]

How about an inverted king post.  The post could be a slipped into a pipe socket and once folded out the cable would hold the pipe/post  in place.

[rickeieio]

8 hours ago, J-T said:

How about an inverted king post.  The post could be a slipped into a pipe socket and once folded out the cable would hold the pipe/post  in place.

That's what I was thinking, except attach the post to the hinge so it folds, and stows, inside the ramp.  By adjusting the cable length, you could also put a  little arch into the ramp.

[SuiteSuccess]

10 hours ago, J-T said:

How about an inverted king post.  The post could be a slipped into a pipe socket and once folded out the cable would hold the pipe/post  in place.

Very interesting.

[wtgeodog]

I place 3 Ton jack stands on the hinge points of the ramps  to load and unload our smart4two.

It might be a "Belt & Suspenders" operation, but I know the hinge won't fail.

 

ShortyO

[Ronbo]

The kingpost wouldnt have to reach the ground if the cables were strong enough. I want to see pictures in use.

[GeorgiaHybrid]

Guys, the kingpost is a good design as long as you stay within the design limitations that it has. The connection of the kingpost to the beam must be a rigid connection and in this case, must be connected to both members on each side of the hinge. Ideally, it should have a base plate with 4 bolts which is almost impossible in this case.

When you invert that kingpost however you can run into some VERY serious problems. If that kingpost ever gets out of a vertical plane, it offers little support. Think of a regular, above the beam kingpost design. If the post starts coming off of the vertical (say 80 degrees), the beam will sag and force the kingpost back into a vertical position. This will happen due to the camber that is placed into the beam to help make this type of truss a stable structural element.

In this case, with an inverted kingpost, if the post ever gets out of a vertical position, it will allow the beam to flex further, which in turn allows the king post to go even further off of the vertical. This is a cycle that can only end with one result if you are depending on the kingpin truss to resist the loading.  If the simple span beam is overstressed and requires the truss to remain a rigid member, it will fail at some point.

A flitch plate (fish mouth) will reinforce the ramp at the hinge which is the weak point of the ramp. If you do use the inverted kingpost, make sure that you have a GOOD, SOLID, 4 bolt connection to the ramp with a baseplate that is 3x5 or 4x6 inches in size and bolts to both sides with the bolts in the corner of the plate. My ramps will not allow that but there might be some out there that will.

[ALLOY]

11 hours ago, rickeieio said:

That's what I was thinking, except attach the post to the hinge so it folds, and stows, inside the ramp.  By adjusting the cable length, you could also put a  little arch into the ramp.

The post(s) don't need to be very long (12" -18") but it needs to be 1 1/2" or 2"sch 40 alum pipe and  fixed firmly or lateral (scenario that GeorgiaHybird mentions) failure will occur.  Connecting the post together in a H format will also add lateral support.

Holes can be drilled through the web of the ramp at both ends so the cable passed through and crimped  in place or shackles may fit.

 

 

 

[noteven]

This could be an app for a #8 Skyhook

[GeorgiaHybrid]

31 minutes ago, noteven said:

This could be an app for a #8 Skyhook

Sounds like we have an ironworker on the site.

[noteven]

12 hours ago, GeorgiaHybrid said:

Sounds like we have an ironworker on the site.

Na ... but what we would do in the oilpatch is a. use a ramp that is strong enough or b. join the ends with chain and ratchet-binder a bit of tension/arch into it so if the ramp wants to deflect it has to stretch the chain...  a. being the much preferred option at all times...

[GeorgiaHybrid]

We used two different ways in steel.

When in doubt, make it stout.

The moron theory, when in doubt, add more on.