Counter weight

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guymac

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If I project two beams from a building by 3 meters what amount of counter weight would I need ?
Would normally jack into concrete ceiling but due to pipes cables etc cannot . Did have a formula when I did my part two but lost it . Scaffold is only one boarded lift directly off the beams to support max 200kg . I will get engineers drawing just want a rough estimate . Cheers
 
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It is fairly simple to calculate but some more information would be required.

I assume the 3m is from where the beams are supported to the end of the cantilever? If so how much of the 3.0m is boarded?

How long is it, you say two beams but how far apart are they?

Most important, what is the tailback...meaning how far do the beams extend into the building meaured from the support position.

You could always give us a call on Monday and I'd have no problem talking it through with you...and maybe we could do that full design you mentioned.

PM me for details.
 
Defo get a drawing mate... roughly if you count a foot of tube as 3lb, and each fitting 3lb.. then x by 3 thats pretty near...
 
Will do I have to meet lift engineer 08.00 Monday . Scaffold platform will be 2.5 long boarded and four boards wide . I only have 1 to 1.5 m of beam on the landing . If I could ring you would be great but I still cannot work out how to PM any body . My phone number is 07977 237175 mail max.access@ yahoo.co.uk . Thanks in advance
 
The formula your looking for is

WxP
_______ x 3 (memorise it as it rhymes, W times P over T times 3)

T

W= Weight , the weight of the scaffold from your fulcrum point outwards
P = Projection, the length of the protrusion of the beams from the fulcrum point
T = Tail, the weight of the scaffold from the fulcrum point going backwards into the building.

Basically multiply the weight (W) by the Projection (P) then divide the answer by the Tail weight (T). Then multiply the total by 3. This will give you the required backweight / Kentledge.
 
guymac said:
Will do I have to meet lift engineer 08.00 Monday . Scaffold platform will be 2.5 long boarded and four boards wide . I only have 1 to 1.5 m of beam on the landing . If I could ring you would be great but I still cannot work out how to PM any body . My phone number is 07977 237175 mail max.access@ yahoo.co.uk . Thanks in advance
Click to expand...

If it's a lift shaft rig could you not bolt the beam directly to the wall meaning you won't have to bother with the kentledge?
 
Deemess said:
The formula your looking for is

WxP
_______ x 3 (memorise it as it rhymes, W times P over T times 3)

T

W= Weight , the weight of the scaffold from your fulcrum point outwards
P = Projection, the length of the protrusion of the beams from the fulcrum point
T = Tail, the weight of the scaffold from the fulcrum point going backwards into the building.

Basically multiply the weight (W) by the Projection (P) then divide the answer by the Tail weight (T). Then multiply the total by 3. This will give you the required backweight / Kentledge.
Click to expand...

Care needs to be taken here.....the formula is incorrect at a number of levels:
The W does not include imposed loads...only the "weight of the scaffold"
T (noted as the weight of the scaffold going back)...this should actually be the DISTANCE from the fulcrum to the CENTRELINE of the counterweight (kentledge) to find the counterweight required.
 
so your saying axsd ,w should include max weight going to be carried by the scaffold and you should keep your kentledge spread out evenly and hit its centreline,not really understanding the centreline bit as if the kentledge is unevenly or evenly spread across a wider area wouldnt that effect the fulcrum point :confused:
 
The fundimental principals of the calculations is correct...the self wiight and the imposed load appled to the structure will be controlled by additional ballist as required...
 
AxSD said:
Care needs to be taken here.....the formula is incorrect at a number of levels:
The W does not include imposed loads...only the "weight of the scaffold"
T (noted as the weight of the scaffold going back)...this should actually be the DISTANCE from the fulcrum to the CENTRELINE of the counterweight (kentledge) to find the counterweight required.
Click to expand...
Oh dear......I seem to have upset you by giving away trade secrets.

To state its wrong on a number of levels is wrong.The guy knows he still needs a drawing regardless, so dont worry your job is safe.

What he asked for was a rough idea.

This formula was taught to me at Bircham Newton 34 years ago and has stood the test of time with all i have built.
Imposed loads would obviously be added, e.g. snow loading if applicable or if he was holding the International Pogo jumping contest then shock loading would be a factor but it was stated 200kg.

Very pedantically pointed out about the centreline of the kentledge, any scaff would apply the counter weights at the rear so thats taken as an industry norm. I stand by the formula and the fact that drawings are still required for such like.
 
so build it,find out imposed load then add more kentledge as required ?

nice to see better educated people also having a ding dong ;)
 
joebag said:
so your saying axsd ,w should include max weight going to be carried by the scaffold and you should keep your kentledge spread out evenly and hit its centreline,not really understanding the centreline bit as if the kentledge is unevenly or evenly spread across a wider area wouldnt that effect the fulcrum point :confused:
Click to expand...

What I am saying is:

The load on the cantilever should include imposed load as well as self weight.

Put the kentledge as far back from the fulcrum as possible BUT the distance taken must be from the CENTRELINE of that kentledge measured from the fulcrum.

PLEASE NOTE THE CALCULATION SUPPLIED IS INCORRECT - FOR THE REASONS I PREVIOUSLY HAVE GIVEN.

---------- Post added at 12:51 PM ---------- Previous post was at 12:48 PM ----------
Deemess said:
Oh dear......I seem to have upset you by giving away trade secrets.

To state its wrong on a number of levels is wrong.The guy knows he still needs a drawing regardless, so dont worry your job is safe.

What he asked for was a rough idea.

This formula was taught to me at Bircham Newton 34 years ago and has stood the test of time with all i have built.
Imposed loads would obviously be added, e.g. snow loading if applicable or if he was holding the International Pogo jumping contest then shock loading would be a factor but it was stated 200kg.

Very pedantically pointed out about the centreline of the kentledge, any scaff would apply the counter weights at the rear so thats taken as an industry norm. I stand by the formula and the fact that drawings are still required for such like.
Click to expand...

I am certainly not upset....but the formula is wrong. The T part of the formula you provided is incorrect - not being pedantic, it's just wrong!
 
might be a case of experience over science here mate,think what the blokes are saying is as a scaff using that formulae and memorising it will stand you in good stead,wheras from your point of view the imposed load and kentledge centreline should be as important to add on,will take both views and apply them,best of both worlds the forum ;)
 
Joebag you summed it up on that first line, although you would probably know what the imposed load was going to be before you built it.

Oh ..and im not educated,not a design engineer, a normal scaffolder, i went to Govan High. (same as sir Alex)
 
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