Reinforcing 12 Inch deep pattern for green sand?

Discussion in 'Sand Casting' started by Mark's castings, Oct 9, 2021.

  1. Melterskelter

    Melterskelter Gold Banner Member

    Cables tend to occasionally not spool smoothly with a wrap “stacking” onto a prior wrap and then slipping of giving a jolt to the load. Jolting is the last thing we need. The strap just spools on and off with no drama. Being a bit stretchy also smooths out the lift a bit. Anyway, it is sweet.

    Retrofitting a worm gear onto a spur gear hoist will take a fair bit of time. Here is a 50-dollar off-the- shelf winch with 20 times your needed capacity. https://www.amazon.com/XtremepowerU...eywords=Worm+gear+winch&qid=1634562861&sr=8-4

    Denis
     
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  2. Petee716

    Petee716 Gold Banner Member

    That's exactly the model I bought from Harbor Freight. The nice thing about the worm is that it doesn't require any kind of braking. I just had to turn a coupler to attach the drill motor. I initially had a cheap 3/8 drill motor on it which worked well until i had an actual load on it. The magic smoke came out immediately. The 1/2 motor works without complaint. I bought a foot switch for it.
    As Denis mentioned earlier, lifting the entire mold to let it self-center under the winch before lifting the cope takes alot of the alignment issues away as well as much of the anxiety.


    +1
    I just finished turning one for my lathe and Denis is right, alot of work. It's certainly in your wheelhouse, but the above linked winch is a slam-dunk.

    Pete
     
  3. Thanks for the feedback gentlemen, for some reason I missed both your posts until just now. That's the first worm drive hand winch I've seen like that, I have a 550Kg 1:4 gear drive unit with the usual ratchet pawl to stop rotation, so it'll be easy to lift and a nothing to stop it crashing to the ground on lowering. It should be possible to get nylon webbing for a custom winch, like a drum on a mains powered motor + worm drive gearbox.

    hand winch.jpg


    D'OH!!!, just remembered I have these salvaged 24 volt 120 Watt 1/6th HP electric motors with worm drive and a suitable power supply for them. They have taper lock flex rubber couplings for misalignment, so with a spool on bearings fitted, I have a ready made electric winch unit! :D. looks like they are 1:28 so that would be 54 RPM with the 1500 RPM motor.

    right angle motor.jpg
     
    Last edited: Oct 20, 2021
  4. Petee716

    Petee716 Gold Banner Member

    That motor would actually be a better setup than my drill motor: simple F/R switching, variable speed, probably smoother jogging.
    For my strap I just bought an inexpensive tow strap. It already has a securely fastened hook. I just prewound it on the spool to find out how many wraps it would take and cut off the excess. I drilled a few holes in the end and secured it to the drum. Once it has a couple of wraps on it, there’s no concern about the holding strength. The downside with that strap is that the hook doesn’t swivel. Because of my ceiling height, every inch matters, so I just have to deal with it.

    Pete
     
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  5. Hmmm, I've got a new ratchet strap 3" wide with hook fitted that's been sitting around for ages that would be ideal. I'll just have to fab a frame for the spool shaft and fit some small tapered roller bearings I have lying around. This is looking pretty good so far.
     
  6. Melterskelter

    Melterskelter Gold Banner Member

    Use a pulse width modulator to control your 24v DC motor and then you can have variable speed. I use a couple of them in my shop. They are dead easy to install and are inexpensive. Here is one example:
    https://www.amazon.com/RioRand-7-80...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

    24v DC power supplies are also widely available and cheap as you likely know.

    Some sort of swivel bolt or clip might be a nice termination for the strap.
    https://www.amazon.com/DGOL-Trigger...3,B08BFHRD3J,B07SSXZWVB,B07XQ7D1GW,B08C9TBD4S

    Denis
     
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  7. Chazza

    Chazza Silver

    I love the creativity going on in this thread especially with the lifting gear.

    Having spent 21 years as volunteer emergency rescuer, I suggest the following.

    Ropes and webbing (tape) bought at hardware stores, is often not rated and of low quality; so if you are planning to lift loads, which you would struggle to lift by yourself, it is wise and safest to purchase the best quality.

    For your winch Mark, you might like to consider this tube-tape; it can usually bought by the metre. Safe-working-load 225 kg for a single line.. https://www.mont.com.au/products/25mm-tube-tape. If cost is a problem, old seatbelts from a car make useful slings; I have used them to lift engines from cars and they are usually free. When cutting slings/tape/webbing, use a hot knife which melts the fibres together; I use an old hacksaw blade with a ground edge.

    Flat tape should be joined with a follow-through thumb-knot, any other knot will slip.

    Denis, I think I saw on your attached movie, cotton ropes on your lifting device. Cotton sucks in the strength dept and it can degrade quickly in damp conditions. May I recommend this superior product? https://ropegalore.com.au/o6mm-donaghys-response-accessory-cords/ It can be bought by the metre if you shop around. Normal knots can be tied in it; safe-working-load 85 kg for a single line.

    And finally; if you suspend a load with multiple lines, such as, slings, ropes, chains, or tape, the angle between those lines must never exceed 120 degrees and is best at 90 degrees or less. This is because above 120 deg. the lines start pulling on each other and it is easy to overload them and cause a failure,

    Cheers Charlie
     
  8. Melterskelter

    Melterskelter Gold Banner Member

    Nope, nylon web just like a seat belt. Breaking strength 4000 pounds. Max load 550 pounds.
    4DA25332-B24C-441D-B851-EA573FC67B34.jpeg
    Denis
     
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  9. That's some very good advice Charlie, I wasn't aware of the 90 degree or less rule of thumb. For $16, I can get a 50mm wide 2500 Kg "Lashing Capacity" tie down, I don't believe for a second that equates to 2500Kg lifting capacity. The plan is to lift no more than 100Kg maximum as the overhead steel purlin would be a major limiting factor as well (and need reinforcement/bracing).

    GRTD0069-2.jpg
     
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  10. Now that I have a design I'm happy with, the construction could start. The base is a 4" web aluminium channel with some 16mm aluminium plate bored to fit some 3/4" bore GMH stub axle tapered roller bearings which could then take some 3/4" 316 stainless as the shaft to wind 6 metres or 20' of 50mm/2" nylon strap onto. I have some stainless discs to bore and weld to the shaft to form a take up spool for the strap. I'll have to pack the gearbox to the right height once the shaft is machined for the taper lock hub and threaded for a bearing preload nut.

    electric hoist 3.jpg

    electric hoist 2.jpg

    electric hoist 1.jpg
     
    Last edited: Oct 23, 2021
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  11. Melterskelter

    Melterskelter Gold Banner Member

    Maybe shimming the motor to exact height to match the strap axle will be just fine. But if there is room, some sort of a forgiving coupler would be a plus. I am thinking of something like a Lovejoy coupler which would allow for slight untrue ness of rotation, height, and angular misalignment. To connect my drill motor to the winch shaft, I used a simple drive socket and loose fitting hex on the shaft. In that case I knew for sure neither the chuck nor the winch shaft ran true, but the socket allowed mismatch without binding. Simplest case might be to drill 9/64” hole in the driven shaft and make a loose coupler with plenty of clearance with a 1/8” roll-pin to drive the driven shaft.

    F12847DC-FB34-4CDB-A2A2-77CE89E84AA3.png


    What you are making looks very robust and far more than adequate for the job. Nice work!

    Denis
     

  12. Hi Denis, I'd rather over engineer it than under, not that it'll ever be lifting engine blocks or similar. The worm drives came with such a coupler: it's that black iron unit between the worm and the shaft, I'm not sure of the type but it has a 15mm bore taper lock with a keyway for the winch side of things.

    flex coupler.jpg
     
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  13. Peedee

    Peedee Silver

    That's a cush drive coupling, i'm not sure how much lateral movement they tolerate? I though they were general used as a 'soft' coupling but may be worth a google.
     
  14. I did that and googled the topic: they are jaw type couplers and can tolerate some misalignment of the shafts. Different hardness materials for the spider can vary the cushion effect all the way up to bronze for a hard coupling.
     
  15. Today I finished off the winch: machined some aluminium packers for the worm drive and shimmed them to the final height with steel shims so that the jaw coupler has a slight gap that is consistent and concentric to each half. The strap initially used some duct tape to attach to the shaft but under tension it wound up tighter and snapped the duct tape before free wheeling, so I moved onto the original plan and cut a lengthwise slot through the shaft with an angle grinder and finished with a "Poor Man's Milling Machine": three blades mounted in the hacksaw frame to cut the ends of the slot to full depth. Some emery tape smoothed the inside and put a gentle radius on the slot corners to prevent damage to the polyester strap. I had some 6mm thick stainless steel discs lying around as scrap that were bored and small hub tack welded on to form the spool for the strap. The hoist is held up with four bolts to the steel purlin and runs smoothly off a small 12V gel battery but I can see that a 24V power supply will give better power. I jury rigged a chain through a bit of pipe to form a stirrup on the end of the strap and I put my the full weight of my fat ass on it: 110Kg and it actually slowly drove the worm drive backwards after a while so full weight limit is going to be about 80 Kg or so which should be fine for my purposes. So back to the main programming again.

    shaft slot.jpg


    spool sides.jpg


    strap fitted 3.jpg


    hoist fitted.jpg
     
    Last edited: Oct 26, 2021
  16. Petee716

    Petee716 Gold Banner Member

    Well there you go! I'm surprised the worm goes backwards. I thought its basic physics would prevent it, but, wrong again! And I've never even thought of putting multiple blades on a hacksaw frame. Imagine the possibilities! Lol.
    Nice work by the way.

    Pete
     
  17. Thanks!, as a kid I found that out from an old marine radar antenna, I used to wire up a car battery to the worm drive motor and freak out the neighbours!. You could spin up the motor pretty fast by using the antenna as a lever.
     
    Last edited: Oct 26, 2021
  18. Melterskelter

    Melterskelter Gold Banner Member

    I am surprised that your worm drive will reverse as all the worm-gear winches I’ve been around and used will not. The Dutton-Lainson I used shows no inclination to freewheel even with 550 pounds on it. But, in theory and practice a worm can reverse as it is ultimately relying on friction on an inclined plane for breaking. I suppose that he engineers designing worms for winches do so with that in mind. Here is an article that speaks to this question:
    https://www.machinedesign.com/motors-drives/article/21834661/selflocking-worm-gears-fact-or-fiction

    In the FAQ’s section of Dutton-Lainson’s site they indicate that their worm winches are self-locking.
    “Q. Is it necessary to have a brake winch for vertical lifting, or will a pulling winch work?
    A. A self-locking winch should always be used in any situation that involves vertical lifting. DLB-series or B-series brake winches or a worm gear winch should be used to avoid the potential of a load free-wheeling out of control.”

    Your build looks very good. Considering all the other work you did on this winch, itwould not be hard for you to add a brake for larger loads if desired.
    Denis

    Added: It also occurs to me that a drill motor itself has very strong anti-freewheeling characteristics. That is why my keyless chuck works so well. It is possible to drive the motor with a good-sized hex wrench in the chuck, but it ain’t easy. So, the combined inherent design of DL worm winch plus a drill motor makes a very self-locking winch setup.
     
    Last edited: Oct 26, 2021
  19. More testing will be necessary once I build a suitable power supply, the 4 amp hour gel battery didn't last long when loaded, I switched over to a 12V 16.5 A power supply (Xbox 360) but it went into overload and shut down without too much loading. When you think about it a radar antenna would be a special case low reduction ratio worm drive to spin the antenna quickly which would make back driving easier, especially with the leverage of the antenna width. I have some older nicad Makita drills and they all seem to have a freewheeling clutch that audibly click in when they stop, so it's not just the multiple planetary gear sets doing the heavy lifting so to speak. Those one way roller clutches are dead easy to fit, if only there was an electric release version out there somewhere. It may be that a gear on the spool shaft with a solenoid released, spring driven gear segment to jam rotation unless energized.
     
  20. Rigged up a control box with up and down buttons that control relays to activate the motor and cut power to the opposite relay via "normally closed" contacts: this ensure only one relay can be active at a time to prevent shorting out the power supply if both buttons are pressed at the same time o_O. On a bad note, the unit can only hold 20Kg but when going down, the 28:1 worm drive will run away until the load hits the ground. A 40 Kg load will lift fine but immediately runs away and accelerates until the load hits the ground. I fired a query off to the manufacturer and they immediately got back to me with a quote of $120 for a 60:1 reduction box, it's based on a standard NMTV-30 size but has a tiny jaw coupler on the input shaft which may be non standard. So I estimate I'll have $200 in this project once it's done and dusted where a budget 50Kg electric hoist would cost $113 from the hardware store.
     
    Last edited: Oct 28, 2021

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