THE MILLER FOUNDRY

 

 

THE FORKLIFT PROJECT:

I have this crazy idea that I would like to own a forklift! Not very practical since I have no way to transport it and no where to park it. And why exactly do I need a forklift? Need is maybe too strong of a word. I was thinking it would be useful for moving items in the garage, loading a pickup truck, moving furniture and lifting heavy casting flasks (in place of a hoist.) Maybe taking out the trash like a real man. With that in mind, my target objectives are: lift capacity- at least 500 lbs to be usefull i.e 1/4 ton pickup. forks would be 24" apart and 36" long. Able to lift a light pallet. small size- wheelbase able to fit through a standard doorframe. My shop door is 30". The mast should be able to fit under a 7' door frame. This will obviously limit my lift height. light weight- will need a heavy counter weight but I would like to be able to transport this on a utility trailer. I will try to keep the vehicle weight at <1000 lbs. with the counter weight removable. electric propulsion - not as sophisticated as Anons. Maybe 24v wheelchair motors geared down. Speed is not too important. cost - this is really kind of frivolous so I cant break the bank. I could buy a decent used forklift for a couple grand. Probably can't use hydraulics. I should note, I am not sure this is really a casting project but I can see alot of parts that will need to be cast. Also it will be a useful foundry tool. So what do yall think? Would you find uses for this? Will this be another unfinished (or unstarted) project?

This design is more current using a 10" front wheel

Here are the motors I am planning on using:

Here is some detail of what I am thinking so far: I was planning on a fixed solid 1" front axle which would carry 10" wheels with roller bearings. The wheels (I have already ordered) will be polyurethane on iron. They are rated at like 2000lbs. I will attach sprockets to these and drive them with a #40 chain from the wheelchair motors. That takes the static load off the motor shafts. This is the front wheel

Here is the front axle and motors

For the rear wheels I was planning on using casters. I have two 6" poly on aluminum casters each rated at 1200 lbs

I was not planning on having a suspension. Maybe that is not such a good idea? I may build it without, and add suspension to the rear if needed. I also considered a three wheel design but it seemed tippy. My plan is to steer it like a wheelchair using the joystick controller. I hope the rear casters will swivel OK under load. For the masts I am using a 3 x 6" rectangular tube cut lenghtwise with a plasma cutter. This creates 2 U channels with parallel walls. I have large bearings from an Xray table that will ride inside these. The bearing are 2" dia by 1/2" wide and are probably rated around 10K to 20K lbs static load.

These bearing will be carried by a steel frame and the forks will hang on that. I had planned on about 13 or 14" between the upper and lower bearings. With 500 pounds at the very tip of a 36" fork, that puts a force of 1500 lbs distributed between 4 bearings. I think I have a line on a winch to raise the forks but I don't know much about winches. I can pretty easily add a safety lock if needed. Here is a cardboard layout of the base

I had planned on sitting on this thing but that will be the last decision. A seat is $5. So here are a few questions:
1. Is a 1" mild steel axle capaple of carrying this load without bending?
2. Will the casters swivel OK and allow steering?
3. Will a winch cable get pulled back out with the power off? ie do I need a solenoid lock? Do winches run in both directions under power or do I need to figure out a way to lower the load slowly?
4. How much should I gear down the motors? With vehicle and payload at 1500 lbs I am thinking 3:1 or 4:1
5. Should I make the base longer than 48"? I looked at a real lift truck (small) and I was pleased to find it was also only 30" wide. It weighed 7800 lbs!

 

How critical does everyone think the mast tilt will be? I am primarily using this on the driveway and in the garage. I am trying to keep it simple. I may build a fixed mast for proof of concept. The tilting mast could be phase 2. I like the idea of a large pivot at the bottom and a motor driven screw or car jack. I could use a C-clamp lead screw on each side synchronized by a chain. I have seen the forklift project from Vintage Projects. Something like that only heavier duty. I thought about using a chain to raise and lower the forks but chain is way more expensive than wire rope and I would need to modify the winch. Also, I can unhook the cable from the forks and use the winch to pull something or route the cable thru an overhead pulley. Very versatile. Who can give me some input on how winches work going in and out? I invite further discussion on questions 3, 4, and 5. Just to post some pics; how's this for a forklift?!

I considered raising or lowering the rear wheels but that may be even more complicated since they need to stay level to the frame. How about a pivot for the mast like this attached to the lower frame:

W3- I was thinking about your idea some more and I think a slight modification might make it workable. The casters will only be a problem if they are tilted excessively. I could mount the base plates on long arms. Kind of like a trailing arms in a car suspension. The pivot point could be in front of the rear wheels near the mid-point of the frame. That way when they move down the angle does not change much. I could use a linear actuator (see Northern Tool) to move the wheels up and down. Anyone know a cheaper place to get a linear actuator with a 3-4" stroke? Any other thoughts? Here is a mockup of what I am thinking. The linear actuator would sit over the wheel base and push down.

Here is the basic layout I am planning:

Here are patterns I made for aluminum blocks to carry the axle:

Waiting for lots of parts in the mail and another trip to the surplus store. I am really trying to keep the cost down but its not so easy. The front wheels were critical so I spent the most there. Pics when I get them. I cast the axle holding blocks.

The left one is petrobond (homemade) The right one is greensand. I am taking W3 and pie-row's suggestions. I will build a subframe to carry the rear wheels. It will have a pivot just benind the front wheels and a linear actuator with a 3" travel. That will tilt the entire vehicle including the forks. The subframe will stay parallel with the ground. Got the front wheels today! Pics to follow. R

I found a sprocket for my motors but the bore is 1mm smaller than the shaft. I could machine it out on my lathe but it is "hardened" steel. I assume that means case hardened or heat treated or both. Can I machine that using a carbide tool? Will I definitely trash my tool? I have never tried it before. Let me know if you have experience.

 

Good advice as usual! I tested the inside of the sprocket with a file and it did not seem that hard. Heat treated maybe but not like tool steel. I chucked it up in my lathe and... no problem. The carbide cut it nicely with a great finish. I took a few 0.1mm passes and fit it onto the motor. I fabricated a key from keystock. A little tricky cause the keyway in the sprocket is 3/16 and the shaft has a 6mm keyway! They look good.

Here is the drive sprocket mounted

Here is a mockup of the base with the wheels. Note the subframe carying the rear wheels. That will tilt down.

Here is a closeup of the rear wheels and carrier.

I had four days off and I have made progress! I got a UPS package!

These are the bearings that will carry the forks:

Here they are fitted on the frame. This will run up and down the mast. The frame is 1/4" thick steel angle and 1/2" steel.

This is a pic of the chain drive from the motors. I Drilled holes in the sprocket and drilled and tapped holes in the wheel hub to fit .

Shaft support. Cast!

Both motors mounted. Will it run???

Test setup with two jump boxes:

The base actually drives very well. It is not yet at its full weight. I am a little concerned about motor performance when all the steel is added. It seems to carry me and the dog pretty well! Turns and maneuvers well. This is really a complex project. It is really 3 projects: the mast and fork carrier, the drive system, and the frame and tilt mechanism. Lots of welding; sorry not alot of casting. I need to cast a pulley for the lifting cable. I will be back with some casting pics! R Edit: Thanks for the info on the batteries. I may do that eventually. For now I have a used car battery and boat battery. They will get me by until I am sure I am satisfied. The rear actuator arrives tomorrow. I can wait to see how it works for the tilt mechanism! I need to find some steel or iron for counter weight. Im thinking about rebar packed into PVC pipe. Any other good/cheap ideas? R

Here are some more pics as this develops! I got a linear actuator on Ebay with 1000 lb capacity. Which one of y'all was bidding this up?

You can see the top frame as well. Here is the actuator mount on the sub frame. It is cast.

The actuator in the up and down positions. This should provide adequate fork tilt:

The vehicle now weighs about 220 lbs. I loaded the rear of the vehicle with a 110lb anvil, an 86lb piece of cast iron, and two adults! It moved and turned fine carrying all that weight! So far it seems like it will work. I figure the gearboxes for the motors are the weak link. I could get heavier motors and gearboxes if needed. I have the mast coming soon. My brother plasma cut a 3 x 6 rectangular tube into two U channels. Thanks Erik! I need to machine a pulley for the top of the mast to lift the forks.

Big Egg- I'm not too worried about tipping sideways. I plan to use this mostly in the garage on a level floor. Also, I found a real forklift with a 30" wheel width; same as this! I will plan on lowering a load to the bottom before I move it. In other news, I started to machine the pulley for the top of the mast. I used a 1" x 3.5" aluminum blank that I had handy. I have 2 bearings coming that will fit in the center hole.

Here are the latest. I machined out the center hole of the pulley to fit the bearings. These ride on a 1/2" bolt for an axle:

I got some steel plate for the floor and put in the batteries to see how they would go:

I do not have the mast yet but I started on the forks. These are made from 1 x 3" 0.120 wall tube. $47 for 20'. Not bad.

No that is not the prettiest TIG weld I have ever made but I was going for penetration and trying to add alot of filler. This joint will see alot of force. I may add gussets on the sides. Here are the forks and the hanger mechanism:

These are 36" long.

Mast pieces should come tomorrow. That will be interesting.

I am back with more pics. The mast turned out to be alot harder than I figured. If you remember, I started with a 3x5" rectangular tube and I had it cut lengthwise to yield two U channels. Well, the two channels were significantly bowed after cutting. I cut three pieces of wood to act as spacers to try to get this all straight. Here is the assebly clamped up prior to welding:

The middle clamp is under significant force to straighten out the bowing. I welded on four cross braces but it was not straight. I ended using up 5 cross braces. I also had to cut loose two braces and reweld them to get it close. Now the two channels are straight and parallel to within <1/16". I think that will be good enough.

Next I turned my attention to the mast struts. I had some 1" pipe already so I used it. I needed one end to be adjustable for length. I decided to machine a nut to fit inside the pipe and weld it in place. The rod ends came from Interstate Surplus (local) and were basically free!

This is the other end of the strut:

Here are the completed struts:

Here they are mocked up with the mast:

This is a big vehicle to be building in my little shop! But I am starting to think this might work. I have a winch coming next weekend. Next project is figure out the wiring.

I considered using a snatch block on the carriage. Here is the issue. The fastest winches are rated at about 15ft/min with a load of 500#. If I use a snatch block (one pulley) it would take a full minute for fork travel rather than 30 sec. Besides, even with 1000# on the forks I should be well under winch capacity. I think it will work ok. Here is the winch I bought.

The Warn 25RT supposedly has a brake to keep it from winding out with the power off (mechanical and dynamic). I assume dynamic braking is shorting the motor leads. The specs say the Rated Line Pull is 2500#. As far as I can tell from the literature Rated Line Pull is the force the winch can generate using the first wrap of the drum. If I don't have this correct please send me a reference source. BTW as long as it pulls 750# it will work OK. I may actually enlarge the drum diameter to get more line speed if it can handle it. http://www.warn.com/atv/winches/RT25.shtml

Here are the pics of the winch modification to disable free-spool. This is the clutch end of the winch:

If you remove the cover you will see this spring plate:

This is the pin that moves out to enable free-spool. There are two.

Here is the plate I fabicated to lock the pins in:

Installed:

This holds the pins firmly in place and I hope will greatly add to the safety of using a winch that is not rated for lifting. In other news I added a step to the rear of the vehicle so one can get on and off. It helps alot.

This is how you treat your finger after welding the step. Not again!?

I am really in the final phases now. I have installed a battery charger and the winch contactor. These will be under the seat (which is not made yet) and above the batteries. "No baby, I don't know where your cutting board is."

Here is the top pulley finished:

I need to figure out the switches/wiring. I have a few mods to make to the lifting carriage. I should be lifting something heavy soon!

W3- The forks are indeed tubing. 1 x 3 x .120. I have added a 45 deg brace on the sides where they meet the upright. You can see it in the last pics if you look carefully. I am concerned about the possibility of fork failure and I will test them carefully and inspect the welds. I have a double attachment where the cable meets the carrier frame for safety . I have successfully disabled the free-spool of the winch. I am adding an electric cut off switch for top of travel. I am pretty sure if you got your arm caught between a mast cross bar and the fork carrier while it was in operation it would not even slow it down! Lets not do that. I feel like I need to add an emergency main cutoff in case of a short or winch contactor sticking, or something else I can't forsee. I am open to any brainstorming about other safety issues. If you think of any failure modes, throw them out there and I will try to address them.

Anon-Excellent ideas. I have considered a panic button but I have yet to find one that will handle the potential amperage of the winch out of control! I think it is a great idea and I will figure out some type of electrical disconnect device even if it calls for a pyrotechnic bolt. Hmmm...where do you buy those. NASA? About the 6 ton crossbow-there is alot of stretch in the winch cable and I could see it snapping back after a failure. I have a #10 screw at the top of the mast pulley to keep the cable in the groove. Here it is covered with a nylon bushing.

I expect that this would restrain the cable and prevent it from hitting the operator. I may buy 15ft of cable and load it up with 1000lbs on the mast as a test. I could cut it with a bolt cutter and see what happens. That would make a great video for this site. Incidentally, yall need to see this video. Its a wire rope break test. The test bed is cabable of 3 million lbs but the rope failed at 1 million lbs. I won't be lifting that much. http://www.youtube.com/watch?v=WRsOSU5U0X4

Well I have been working on the wiring and safety issues. First I needed a way to attach the cable to the fork carrier. I wanted to have a backup attachment in case of failure of the attachment. I wanted to use the existing factory swage fitting with the loop but I did not want to rely on that alone. Here is what I came up with.

As you can see, I fabricated an aluminum cable stop that clamps to the cable with 6 screws. This holds tightly and did not fail when tested up to 1000 lbs. If It does fail it will slide down the cable and impact against the factory swage fitting which should hold as a backup. The cable is retained between 2 pieces of angle iron and cannot come out. The holes in the metal are beveled and polished to prevent cable fray. This location can also be easily inspected. The rubber band will be replaced by a spring and maintains tension on the cable when the forks are all the way down. The lower limit is mechanical:

The upper limit is a cam/switch arrangement that cuts power to the winch contactor:

This uses a switch from a microwave oven and works great. I get a very consistent limit point. (I was worried about that.) This is the switch box:

This holds alot of wires and the switch to activate the vehicle tilt. Its a DPDT, Mom-off-Mom. The winch control switch is magnetically mounted in front of the box. It is removable with a 4ft cord so you can stand by the forks and watch if needed

Here are a few pics showing the general layout and ergonomics:

 

So now on to testing and I'm sure a few modifications. So far I have lifted 360 lbs. with ease. The cable does stretch a little. I need to take the mast off to get out of the house. I will get some video of it running around the garage. Came out pretty nice so far. Still need to add a battery cutoff switch and panic button. Any other thoughts?

The shop always seems to look cleaner in these camera pics than in real life. There is dust and metal fragments everywhere that don't show up!

The drive motors have some kind of brake. It seems to be a mechanical brake mounted in the box on the end of the motors. When power is cut you can hear the brakes click on to lock the motor. The wheelchair control is great since the joystick inputs are processed by its computer. It will put one motor in reverse and the other in forward to turn in place. The motors start and stop slowly. Reverse is slower than forward. Brakes come on automatically when the motors stop. I have installed chain guards at the motor end. It would now take effort to get caught in the chain. I may put a piece of plexiglass on the back side of the fork carrrier to keep hands out. W3- I ordered that battery isolator you showed me; thanks!

Yes, I will be painting it. That will be a job in itself. The mast will be black. For the base I am deciding between machine gray or safety yellow (with flames.) Maybe keep the vertical tubes black? The floor and counter weights should be black. I also need to get some hot bikini models to lay across the forks for pictures.

Bought this stop button:

This will cut off all power to the drive motors and the winch by opening the relay shown previously. I have to say, I have been driving the forklift around the shop and lifiting various items like my desk and my disc sander. THIS IS ALOT OF FUN! I have a few wires to finish and then I will get it outside. First test is lifting the back of a small SUV!


TESTING:

I finally found time to remove the mast from the forklift and get it out to the garage. The mast could be carried by two people with relative ease. The base was driven out of the house and down a sheet of plywood on the steps acting as a ramp. Only a 2' drop. So far this works great! It can place objects on a 6' shelf or on the rack of our SUV. I also used it to move a casting flask that I previously need help with. This flask weighs over 100 lbs:

I attached a strap:

Used one fork only for this lift:

The lift truck in place for the "big" job:

Its up!

On the floor ten feet away:

I also found this very useful for moving 50 lb buckets of greensand. Cindy just got home with the good camera so I will get some video up next time. I think I need to do a maximum lift test! I have found a few issues in testing so far: the drive motors are geared too low making the vehicle slow. I will change out the sprockets. The winch is too fast. I need to take off some cable layers to slow it down. I may change out the cable for 1/4". Any other comments? P.S. It's ridiculously cold here in NC.

The tilt mechanism turned out to be very valuable and works extremely well. It is also a good way to raise and lower something gently. Im glad you guys suggested that. Yes, it can be broken down and loaded into a pickup or even an SUV if you put the mast on the roof rack. It probably weighs about 500 lbs right now but I have an extra 100 lbs of counterweight not on it. If you take out the batteries and counterweights 2 people can easily move it. But it would be easier to just drive it up a ramp into a vehicle or on a trailer. The winch is a little fast because it stops quickly causing the object to bounce a little due to cable stretch. Part of that is due to the dynamic braking of the motor. I could override that but it is helpful in other situations. If I take some cable off the drum it will pull slower and help with this.

Final Pics:

Here are some action videos!