Suspended Loads

[MattRMagnum]

Hey Folks,

I've had a difficult time trying to Google this topic, so I wanted to ask here:
I want to build three trays (one for each bay of my garage) that are ~2'x1.5', and suspend them in the air. The reason is to store trickle chargers for each car out of the way (and use extending extension cords that will pull out/retract as the platforms are raised and lowered).

I was thinking of using a pulley system, and running the raising/lowering cords over to a single central point on one wall, and screwing a couple bolts into the concrete floor, and using that to anchor them. This made me wonder: where is the majority of the 'load' going to be resting? In my mind, the stress of the weight would be predominantly offloaded onto the concrete floor anchor, and not the pulleys attached to the trusses, correct? Realistically, we're talking about maybe 5lbs worth of load for each platform, so I think the burden on the trusses is fairly minor, but I wanted to ask since a bunch of y'all are far more mechanically inclined than I am.

and, you know, because someone might go "that's dumb, here's a better way to do it."

Oh, and to answer the inevitable why: Which car is in which bay, and whether or not the platform is needed changes regularly, based upon what is or isn't being worked on. I like leaving my cars on trickle chargers to preserve the batteries, but hate pulling them and hauling them to the 'charging station' I have setup in one corner of the garage. I'd rather they just had chargers ready to go, regardless of what car is pulled in.

 

[Dustball]

The anchor point of a single fixed pulley at the ceiling will see double the weight it's carrying.

 

[kbs2244]

primary stress will be on the upper pulleys

 

[BillK]

Matt if all you are talking about is a couple of batter chargers I think you are totally overthinking it. The trusses can surely hold a person working in the attic, I am sure they will have no problem with whatever weight you could possibly put there for a battery charger.

 

[nadogail]

IMHO, you should google KISS System.

 

[The Cobbler]

Your weight load is nothing . don't overthink this. I would actually keep the chargers at an easy to get to location, and run extension leads to hook to the cars .

 

[MattRMagnum]

The anchor point of a single fixed pulley at the ceiling will see double the weight it's carrying.

Really? This is why I asked. I was expecting that there'd be two pulleys: one at the actual vertical point for the platforms, and a second one, at the wall itself, that goes down towards the anchors and the raise/lower mechanism.

Matt if all you are talking about is a couple of batter chargers I think you are totally overthinking it. The trusses can surely hold a person working in the attic, I am sure they will have no problem with whatever weight you could possibly put there for a battery charger.

I probably am. I know there's actually way more than the total load of those platforms already up in the trusses (p.o was kind enough to not clean them out, and not mention it).

IMHO, you should google KISS System.

While historical coding concepts are interesting to me, I fail to see their relevance. Perhaps you meant the KISS principle? In which case, I'm cognizant of it. Thank you for your commentary.
https://en.wikipedia.org/wiki/KISS_(system)

Your weight load is nothing . don't overthink this. I would actually keep the chargers at an easy to get to location, and run extension leads to hook to the cars .

Right now I have them sitting on whatever is in front of the car (couch, bar, workbench) and ferry them back and forth depending on whether the car tucked in the bay needs to be on a charger.

 

[jjkrjh]

You could solid mount trickle chargers on shelf by the ceiling. Install a cord reel that has been modified with alligator clips.

https://www.amazon.com/dp/B07JJ7TWXT/?tag=atomicindus08-20

Have the chargers to switched outlets on ceiling. I would worry about cord security. You would have to have some kind of lanyard or way to keep cord secured to car while the charger is connected. Instead of using alligator clips a dedicated easy connect plug would be best.

https://www.amazon.com/dp/B07KS2GCXJ/?tag=atomicindus08-20

 

[cvairwerks]

Better yet, cord on a reel with something like Anderson PowerPole connectors and a permanently attached harness on each vehicle. Plug in, turn on and no worry about having the hood or battery access open for long periods of time.

 

[matt_i]

I would just do cord reels or dedicated cords (120vac) with a long loop and a hook to hold the female plug, from the ceiling.

I do similar and just put the battery minders under the hood and lightly close it or rest it on the latch-point. They just alligator-clip to the B+ and ground terminals.

Put a wire tag on the steering wheel so you don't forget and try to drive off with the minder still hooked up to the battery....

As far as analyzing the loads on sheaves, the "rope" tension (usually equal to the weight its holding) acts on the pulley in 2 directions. if the rope changes direction 90 degrees over the sheave the resultant vector is on a 45 degree angle in opposing direction, and isn't 2x the load but a vector sum of the "2 tensions"...a sketch would make a better illustration.

 

[sberry]

I have came up with some brain farts too. While its good exercise to explore this kind of idea there are simpler ways. I wouldnt have a problem with a drop cord but would get a simple small charger and put it on a car as needed. Could use the same cord to power work light too.
Second,,, when doing prototype work build 1 first and see how useful it is and if it really works. Lots of this type of thing seems good at the time but ends up abandoned.
You really want a whole bunch of **** rigged all over the ceiling? I had considered a couple different schemes for charging but in the end a couple small automatic portables was the easy way,,, the same way most others do it, for good reason as it was likely the easiest and the best. I do have a station for batteries out of the unit, test and charge but someone gave me the ultimate cart, rigged it up, wheel as needed.
Got rid of the little shelf in the end. That charger is the best I ever owned. Fixxed a couple minor things, snug the connections and dont burn on the booster.
Also I remove the batteries fro the cart, no point in giving them rides around the shop. There is another small automatic on there for grab and go and have another in my storage building.

 

[Bretny]

Matt if all you are talking about is a couple of batter chargers I think you are totally overthinking it. The trusses can surely hold a person working in the attic, I am sure they will have no problem with whatever weight you could possibly put there for a battery charger.

In typical GJ fashion it's over thought.. lol

Suspend them by there cords. They will survive unless we are talking about s commercial battery chsrger on wheels.

 

[Dustball]

The anchor point of a single fixed pulley at the ceiling will see double the weight it's carrying.

Really? This is why I asked. I was expecting that there'd be two pulleys: one at the actual vertical point for the platforms, and a second one, at the wall itself, that goes down towards the anchors and the raise/lower mechanism.

This is the single fixed pulley example- the pulley's anchor point will see both the 100 N carried load and the 100 N force pulling downwards on the rope.

If you're adding a second moveable pulley- it'll go down to 1.5 x load at the fixed pulley anchor point if you arrange it like the picture below.

This page has a good explanation of pulley forces.
https://www.educatedclimber.com/mechanical-advantage-explained/

 

[My Old Tools]

If you are really using trickle chargers, buy 3 and mount them permanently under the hoods. Just plug in when needed.

 

[firebirdparts]

What's missing from discussion about the pulley as a "simple machine" is that if you put 100 pounds tension on a rope, you can run that rope all over the building and put that same 100 pounds into as many surfaces as you want, as many times as you want, and pull the building down with only 100 pounds. The 100 pounds doesn't get smaller unless you do it just the right way (which is to hook the 100 pounds to a bunch of pulleys instead of the rope).

 

[Innovate1]

If you put a pulley over the load and one on the ceiling near the wall with a 100 lb load then each pulley will have 100 lb of downward force. They will also each have 100 lb of sideways force. At each pulley those total to 141 lb of force at a 45 degree angle.

 

[larry_g]

https://www.batterytender.com/4-Ban...er-12V-1-25A-Each-Bank-USA-Western-Hemisphere

https://www.batterytender.com/25-ft-Extension-Leads-4-Pack

Have yopu considered something like the above? Have the cords drop from the ceiling to the car for use and unplugged have a retract that lifts them to ~7' high above the car so that you can reach it next time you need it.

lg
no neat sig line

 

[MattRMagnum]

https://www.batterytender.com/4-Ban...er-12V-1-25A-Each-Bank-USA-Western-Hemisphere

https://www.batterytender.com/25-ft-Extension-Leads-4-Pack

Have yopu considered something like the above? Have the cords drop from the ceiling to the car for use and unplugged have a retract that lifts them to ~7' high above the car so that you can reach it next time you need it.

lg
no neat sig line

I do have one of those already, at my charging station. Maybe ceiling mounting one and running those out would be more sane. I'll have to go out and measure a bit.

 

[ttpete]

Battery Tender Co. makes units that can be installed on a vehicle and hard wired to the vehicle. Using these, all that's needed is to install pull-down reels on walls or ceiling for power cords.