How do scissor lifts control speed?

Parkerbender · Jun 10, 2018

Specifically a Terex TS20 series, about 10-15 years old but i would assume they are all about the same. Are they controlling speed with pwm and using plain switches on the steering and things, not? All dc motors with no feedback? I need to hang the bus duct in my new shop by myself, and found a junk one that needs the contol box... trying to figure out if i could run it with a cheap drive or if i need the actual replacement parts...

Thoughts?

Chip Chester · Jun 10, 2018

Thoughts unnecessary. Just clone the circuitry (or buy parts) from this (likely) manual:
http://manuals.gogenielift.com/Part...aerials/terex aerials/service/17250 (rev).pdf

Larry Dickman · Jun 11, 2018

Parkerbender said:
Specifically a Terex TS20 series, about 10-15 years old but i would assume they are all about the same. Are they controlling speed with pwm and using plain switches on the steering and things, not? All dc motors with no feedback? I need to hang the bus duct in my new shop by myself, and found a junk one that needs the contol box... trying to figure out if i could run it with a cheap drive or if i need the actual replacement parts...

Thoughts?

Picture yourself laying in traction in the hospital, and when the nurse comes in to wipe your ass for you, you start trying to explain to her why you didn't just cough up the 300 bucks to rent a scissor lift. Seems cheap now, doesn't it?

Parkerbender · Jun 11, 2018

If I can manage to tip a lift on flat ground by rebuilding a control, then i probably need to be removed from the gene pool and not be making car airplane and gun parts. Thanks for all of the help, Larry!

Just looking for how they are driven being's I have never been in one. Which, if anyone happens to stumble upon this post in the future looking for an answer, it is all electric over hydraulic. Lastly, thanks Chip for the actual help! That is the correct manual, and it has enough in it to fix the machine.

cg285 · Jun 11, 2018

Parkerbender said:
If I can manage to tip a lift on flat ground by rebuilding a control, then i probably need to be removed from the gene pool and not be making car airplane and gun parts.

yeah, i'm trying to figure out how one would be able to tip over a scissor lift without outside help or heavy equipment.

keyster · Jun 11, 2018

I used to buy a lot of parts from these guys.
Homepage | Access Platform, Inc

Retired now, so it has been a while.

Pete Deal · Jun 11, 2018

I don't know anything about that model but all the ones I have seen/used had hydraulic motors on the wheels and not too much in the way of speed control. I would have thought it was not done by controlling motor speed by controlling flow. And I don't think any kind of proportional flow just like two speeds.

Tony Quiring · Jun 11, 2018

Firgetaboutit. ...

Things that involve human transport have much related to safety...Combine that with transporting said human in a dangerous spot it is multiplied.

A simple wheel chair or scooter control is switching output for extremely fine but tight motor control.

Those with any pots for things will simply not work if any are just a bit off compared to others.

Our gas powered lift has interlock systems to control the valve body and an intermittent connection drove us nuts...short trip...

For an electric lift the motor drivers are likely all switching output and cross linked to sensors that sense level ground as well as extension

If no service manual get one and step through the troubleshooting as it could be simple interlock or foul connection

If bad controller seek out rebuilt or used one.

Yes they can easily tip over...If a narrow unit elevated and one moves the unit while up they normally are limited to very slow creep but a simple "go control" could cause fast change that the extended platform cannot keep up with and over it goes

If for personal use whatever but if any employee is to touch it...This thread is discoverable and would show pre-selecting warning...

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tdmidget · Jun 11, 2018

cg285 said:
yeah, i'm trying to figure out how one would be able to tip over a scissor lift without outside help or heavy equipment.

Ask at U. of Notre Dame. They had someone killed in one a few years ago.

Scottl · Jun 11, 2018

I 100% agree with the suggestion to either repair it to original operation or pass it by.

These are "safe" only if kept in repair and operated properly. When you say you "found a junk one that needs the control box" are you SURE that is the only reason it is "junk"?

If the pivot points are badly worn or there are cracks in the structure the unit was likely scrapped as unsafe to operate. When you say "control box" do you mean the actual control in the base or the remote unit? The latter item is mainly switches and could be reconstructed. Often the problem with them is actually bad wires in the cable.

One point: NEVER operate one when no one else is around. If the remote fails when you are elevated you'll need to have employees around who know how to safely lower the lift from the emergency switch in the base. Otherwise your only option would be to dial 911 and wait for the fire department to rescue you.

Parkerbender · Jun 11, 2018

It appears in the pictures someone must have done something and broke the joystick off of the controller. I really only need to get about 12' up, but after scaling the forklift a couple times to hang each section of this bus duct, though it may drop me a pants size or two, it isnt quick. And you are talking to my employee, osha has no jurisdiction here. I will obviously give it a look see before reaching for the moon, but it appears to be a pretty clear case of someone broke the lift and the 'repair shop' wants more to replace the parts than it was deemed to be worth. If it makes you all feel better, I will take a rope ladder with me. :-)

Larry Dickman · Jun 11, 2018

Parkerbender said:
I will take a rope ladder with me. :-)

something about our attitude really makes me no longer give a shit what you do. I hope the rope ladder was just a joke, hanging your weight off the side is the last thing you'd want to do. You say you've never been on one. Well, I guess that makes you an expert then. So I'll leave you to it.

Scottl · Jun 11, 2018

Larry Dickman said:
something about our attitude really makes me no longer give a shit what you do. I hope the rope ladder was just a joke, hanging your weight off the side is the last thing you'd want to do. You say you've never been on one. Well, I guess that makes you an expert then. So I'll leave you to it.

I suspect the attitude comes from never having worked atop one and being unfamiliar with how dangerous man lifts of all types can be. One of the last things I would ever want to do is climb down from a stuck lift.

dalmatiangirl61 · Jun 11, 2018

If you have a forklift, why not buy/build a proper personnel basket? Do not know about Terex, but Genie lifts use proportional valves to control the hydraulics, if you just used a toggle switch for on/off the starts and stops would be very jerky and unsafe. 10 feet does not look like much from the ground, the perspective looking down is much different.

Tony Quiring · Jun 11, 2018

Scottl said:
I 100% agree with the suggestion to either repair it to original operation or pass it by.

These are "safe" only if kept in repair and operated properly. When you say you "found a junk one that needs the control box" are you SURE that is the only reason it is "junk"?

If the pivot points are badly worn or there are cracks in the structure the unit was likely scrapped as unsafe to operate. When you say "control box" do you mean the actual control in the base or the remote unit? The latter item is mainly switches and could be reconstructed. Often the problem with them is actually bad wires in the cable.

One point: NEVER operate one when no one else is around. If the remote fails when you are elevated you'll need to have employees around who know how to safely lower the lift from the emergency switch in the base. Otherwise your only option would be to dial 911 and wait for the fire department to rescue you.

Funny thing...

Most have emergency decent controls on the platform but ours does not.

Usually have phone while working but got bored on day and decided to work on taking down a eucalyptus tree.

We parked next to it and worked way up cutting branches and while at 20 ft in air ran out of gas... was not a planned event...Just cut a tree..

No phone and the dog was no help.

The tree has ugly branch Stubs and wearing summer cool stuff meant no shimmy down the tree.

About 2 hours later wife came out...

Never work without a ground crew and a phone.

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Tony Quiring · Jun 11, 2018

Parkerbender said:
It appears in the pictures someone must have done something and broke the joystick off of the controller. I really only need to get about 12' up, but after scaling the forklift a couple times to hang each section of this bus duct, though it may drop me a pants size or two, it isnt quick. And you are talking to my employee, osha has no jurisdiction here. I will obviously give it a look see before reaching for the moon, but it appears to be a pretty clear case of someone broke the lift and the 'repair shop' wants more to replace the parts than it was deemed to be worth. If it makes you all feel better, I will take a rope ladder with me. :-)

If the "stick" is broken then that is a servicable part.

Check with unit manufacturer for local to you servicing dealer who may have part in stock and may check yours out.

Not complicated device...similar to old arcade game controller.

The control boards are something else though.

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adama · Jun 11, 2018

Honestly, there just SCR type drives, much like forklifts - pallet trucks have and use and control motor speed through PWM, like damn near any std dc traction drive does. Normally the cleaver bit is some tilt sensors and such. With lift up down and drive - steer theres a fair few drives and controls in there, its going to add up a fair bit cost wise in components alone to even half ass it.

As to being stuck in one, been there done that got the t shirt, fitters thought it would be funny to bang the E stop whilst i was up in the middle of the yard. Thankfully do to a youth spent climbing tries climbing down the side of the thing was pretty simple and pissed em off immensely. Apparently were not supposed to do that under health and safety.

Biggest risk you need to consider driving one indoors is entrapment against something, think uncontrolled raise into ceiling - driving under a low over hang etc. Theres plenty of ways to come unstuck on one with out falling over or off it.

Strostkovy · Jun 11, 2018

adama said:
Honestly, there just SCR type drives, much like forklifts - pallet trucks have and use and control motor speed through PWM, like damn near any std dc traction drive does. Normally the cleaver bit is some tilt sensors and such. With lift up down and drive - steer theres a fair few drives and controls in there, its going to add up a fair bit cost wise in components alone to even half ass it.

As to being stuck in one, been there done that got the t shirt, fitters thought it would be funny to bang the E stop whilst i was up in the middle of the yard. Thankfully do to a youth spent climbing tries climbing down the side of the thing was pretty simple and pissed em off immensely. Apparently were not supposed to do that under health and safety.

Biggest risk you need to consider driving one indoors is entrapment against something, think uncontrolled raise into ceiling - driving under a low over hang etc. Theres plenty of ways to come unstuck on one with out falling over or off it.

They can't use an SCR for a DC motor from a DC source, right? Once you trigger the SCR it would stay on until something broke or the battery died.

Scottl · Jun 11, 2018

Strostkovy said:
They can't use an SCR for a DC motor from a DC source, right? Once you trigger the SCR it would stay on until something broke or the battery died.

I think by "SCR" what he really meant was GTO (Gate Turn-off Thyristor), which can be switched off by a negative pulse. They are not uncommon in dc drive circuits.

adama · Jun 11, 2018

Yeah, sorry, not 100% tonight + was fixing something else last night that has SCR's in it. GTo, power mosfets etc, theres a pretty wide range of devices to do this and more than a few in nice integrated lumps pre attached to heat-sinks with forward reverse and over temp all integrated. Either way its not a cheap or easy project to do, going to cost a lot in bits and large gauge wiring too.

That said, at least over here i would either just rent one or buy one in working order, they don't go for much if the batterys not good and they look tatty (think been used for painting). Equally the problem with owning one is the limitations of what it is. Generally indoors you want one of the smaller genie lifts, then outside you want something with a boom. then add in all the flavours and height ranges, unless you have a good recurring need for exactly the same capabilities, its real easy to be too short or too big to fit into were your going. Hence rental makes a lot of sense.

That said there is a electrician i cross paths with once in a while that has a nice circa 3'x5' one does not go all that high, but plenty for 20' ceilings at least, but no traction motors so its just a powered scaffold, sure you can not drive around up there, but it makes ups - downs real easy and not haveing all the drive motors sure makes it a lot more transportable.

How do scissor lifts control speed?

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