The Stovebolt Site Forums The Parking Lot Tons 'o Fun Blocking the dump bed

Is there a preferred way to block the dump bed while it's up so you can work on wiring etc. below? I know a log might work, but short of that has anyone thought of or developed a mechanical way to block the bed should you want to set it up safely e.g. like on display at a car show? 1948 3800 w/dump grain bed. Thanks for any thoughts or ways others may have approached this, or is this a dumb question?

Dale

When I was working on a dump truck regularly, I fabricated a positive lock from a piece of heavy wall pipe. I split the pipe lengthwise, added hinges on one side, and used the assembly to surround the hydraulic cylinder ram. Angle iron flanges on the opposite side from the hinges allowed me to bolt the lock securely around the ram. I added big flat flanges top and bottom to distribute the load evenly and avoid damaging the cylinder. Just choose a pipe diameter big enough to clamp around the cylinder shaft.
Jerry

That seems a great way to accomplish blocking Jerry. Was there ever a time when that blocker was tested or did you lower the bed enough to engage after you put it in place? A lot of pressure on the hydraulic, but rather it than me - or somebody else.

Dale

Most dump beds lower by gravity with no hydraulic down pressure, so the weight of the bed, plus whatever is inside it is all the lock has to support. I can't imagine many situations where a heavily loaded bed would need to be raised for work underneath it, so the weight of the empty bed, although considerable in some cases, would be all the lock has to support. I always lowered the bed to be in contact with the lock, particularly if I had to work on any of the lift plumbing. Even with a lock in place, I did my best to avoid pinch or crush points whenever possible.
Jerry

Perhaps some USA versions of the hoists lower only under gravity
However there are 6 dump trucks on my farm from 1949-54 on Chevy and GMC, 1-2.5 tons
Every one of them will lower under power
If you hold it in down position you Will hear the engine struggle and all the fine gravel on the frame crunches tight as all the hoses try to straighten out
I’ve never held it in that position too long to find out what gives up
There is no high pressure bypass in the hydraulic system.

Pto off the box can lower under gravity but it won’t be nice and tight to the frame so you get box jump on the bumps which I hate
So I make sure it’s sucked down tight
-s

I was working under two raised dump bodies today ... Both Peterbilts (triaxle and a single axle). Both have positive locks (bars like Jerry described) that raise up and engage the bed so it cannot come back down. We also put wood blocks in closer to the hinges wedged in on top of the frame rails. All of our dump bodies (mostly "East" manufactured and one is a shop built) lower under gravity. Which can be a PITA if, for any number of reasons (most bad), the load does not completely dump and the bed is stuck raised ... but mostly works fine. We have a small truck (IH 4900 single axle dump -- our "sport truck") that has a power down so you have to remember to put the lever back in the neutral position when it is down. It will NOT power down if, say..., an inattentive driver forgets to unlock the gate before raising the bed and the load wedges the gate shut (locks won't release under pressure) ... It wasn't me, but I was part of the shoveling crew to correct it ... at night ... in a blizzard ...

Never EVER prop up a loaded bed, let alone work under it. Dump it in place if you need to lighten the load. Cleaning up a mess is preferable to getting someone hurt or the truck seriously damaged.

2ManyTrucks -- while they might not have put a bypass in the system originally, I would highly recommend putting one in now. That hammer effect is brutal on the pump and the hoses and it is not that complicated to install a bypass. Installing a bypass -- easy. Bursting a line (and having a loaded bed slam down) or blowing up an expensive hydraulic pump truly makes for a bad day ... just sayin'

The experts will know for sure, but I'm guess on the older trucks, a power down ability was used more on the "platform dumps" (dumping flatbeds) than the true dump trucks because the rear axle was set more forward on the frame (and probably so was the hinge point for the bed), so even when empty, there might be more of a tendency for the bed to remain in the raised position, not having enough weight forward of the fulcrum point to let the bed come back down ... ?? Maybe??

We had a friend (who will remain anonymous for obvious reasons) who had that power down feature on his Stovebolt Big Bolt and he bent his bed because a chain remained attached and unnoticed during the power down. So care is needed!


John

Modern dump beds have a piece of pipe secured on one end and have a socket of some sort on the other end to be erected when unloaded. Never use a round log or pipe across the bed to secure a bed, makes dent in back of cab when it rolls out!

Ed

Most of the older gravity-down beds used the area above the piston as a reservoir for hydraulic fluid, and had an air vent at the top of the cylinder. If somebody overfilled the system, the vent would squirt fluid out in a gusher until the volume equalized.
Jerry

The attached pictures show what I did for my '50 Chevy COE. The original bed frame had to be scrapped because the bed frame was bent. A friend fabricated the new frame and I asked him to add the post that you see in the first picture, so that I could work on or display the truck without risk of injury or death. The second picture shows it stowed away; rotated parallel with the bed frame with a bolt through the end holding it in place.
Kent

That is one clean and and very effective appearing dump bed and mechanical blocking device Kent. Just a few questions. Does the lower end secure into a depression or does it rest flat on the housing plate? Do you lower the bed down on to the blocking bar when positioning to secure it? What’s the diameter of the pipe you used, and is it pipe?Have you considered a similar device on the other side to balance the weight of the bed or does ithat not appear necessary given the hydraulic positioning is still employed? I have lots of questions, none of which should detract from the thinking that went into designing this device e.g. built in planned storage for the blocking bar, no need to go too far under the bed to employ, all very valuable features in my opinion. Thanks for sharing Kent, and for the pictures. You have obviously put a lot of thought and work into this.

Dale

Dale,
The pipe is 2 1/2 inch diameter. When deployed, the end rests on the housing plate, over a hex bolt head, which you can see on the left, in the second picture. The bolt head keeps it from kicking out to the side. I lower the bed, using the lift valve knob which is secured to the left bottom of the dash. I can do this by myself, although it is easier to have someone help guide the pipe while I lower the bed.

I only have the one pipe. The valve holds the bed steady, without leak down so ordinarily I use both the valve and pipe at the same time, so both would have to fail for the bed to lower. I have tested it with just the pipe and it seems to hold just fine. I estimate the bed weights 1000lbs, so the hinges hold at least half the weight, so maybe the pipe is holding 500 lbs. I would never use the pipe with a load. First of all, before it failed the frame would twist which would be bad.

When I display the truck with the bed up I try to educate people who stick their head and neck over the frame rails that it could be dangerous, but you know you can't keep an eye on it all the time. At times, I have also included a wood block near the hinges to make it safer but I have never tested this and don't know how much safer that would be.

By the way, I cannot take credit for this design. The friend who fabricated this took my idea and made it a reality. We scrapped the original bed frame and he started over, repositioning the lift on the truck frame because it was not installed correctly and designing hinges with grease zerks built in. I use the bed to haul pine needles from my property (central AZ, 6250 ft elevation with Ponderosa pine) to the dump. The bed is pretty high up so I use a step ladder and fill the bed from the front to the back, a very tiring project. To empty it is a joy, just raise the bed, back up a bit, hit the brakes and the entire load slides right out in one compact fourteen foot long brick of needles.
Kent

Dale, one could use water pipe, schedule 80 pipe, etc. remember, not for a loaded bed!

Ed

Thanks Ed, I'm not sure yet which blocking device I will use , but I have certainly found some great thoughts and designs to take off from. Most helpful. The cautions I have received from you and from other Bolters are experienced reminders of the thought process one must go through when handling this equipment, and they are all certainly welcomed and appreciated. The remaining question in my mind is the gravity vs power lowering that John and others have spoken to. I'm still not sure which one mine is. When I'm pushing forward on the bed actuator lever, it does come down, engine speed does not change appreciably that I can notice, but I'm still not sure. Guess I will have to have someone watch the PTO driveline to see if its turning when lowering? That question seems really important when lowering the bed back down to engage a blocking device, so no harm comes to the system.

Dale

Dale,
I have never dealt with a lift that lowers with hydraulic pressure so I am deficient in knowledge. My bed lowers passively with gravity but it will lower with the PTO turning or with the engine off, as long as I am putting the valve in the down position. Why don't you try lowering yours with the PTO disconnected and/or the engine off. If it lowers, then that is how you would do it to engage a blocking device, regardless of what type you have.
Kent

Concur with Kent -- Follow his guidance.

On my more modern work/job equipment, as soon as the bed is raised to the desired position, I engage the clutch, disengage the PTO and use the raise/lower lever the hold/lower the bed from there. As soon as I am finished with raising the bed, I take the hydraulic pump (PTO) out of the equation to eliminate the possibility of an over pressure that could damage something -- even though there is a bypass in the system.

Remember, though -- operating this Class 8 equipment is a second profession for me and I am far from being an expert, this is just how I have been taught to do it by whom I regard as "competent authority." Let's see what Ed and the real experts have to say.

Another way to secure the bed temporarily is to buy 2 4x4 posts and put in front of the dual wheels by a bed support rail ,lower onto post and that will secure the bed where it will not lower. Pat