There is a difference in belt tensions over the length of the tripper which can be calculated. The resultant component which affects the tripper motion is the difference between the horizontal forces on the discharge & lower bend drums. That depends on the inclination of the belt running between the drums. It's not a lot.

Then there's the external forces like wind, track tolerances, cable reel drag & the material burden components. So 2) - 7) are spot on & I agree with Roland that the burden should also be considered. There is a drag produced along the transistion from the flat beltline up to the first tripper support. Roughly speaking, consider the idlers as pin joints.

If it's a tall unit just beware of wheel spin caused by weight transfer on start up.

Trippers are reasonably challengeing when it comes to detail. i.e should a purist modify the discharge curve to take account of the relative motion of the tripper although the headchute is also moving with the tripper? Purely academic, but there it is. If the belt drive was stationary then the material would discharge or recede according to the tripper movement????■

Originally Posted by designer

I'll start by saying I know nothing regarding the power to drive a belt conveyor tripper (not a lot about belt conveyors either) but I've been asked to suggest a motor power to drive one.

Thinking about it there is clearly the rolling resistance of the tripper due to it's weight and the material load it carries. But what about the effects of belt tension? I'm told that there is a tendency when running for the moving belt to cause the tripper to move.

Anyone care to give me some guidance please.

Further thoughts

1) ignore the material weight

2) consider the belt (loaded with material) as a catenary between the point of tangency with the normal belt line and the point of tangency on the top deflector pulley

3) calculate the belt tension at the top deflector pulley and the resulting belt slope at the point of tangency.

4) trace this tension around the top and bottom deflector pulleys to establish a resultant load

5) add the vertical component to the weight of the tripper to establish the rolling resistance

6) add the horizontal component to the rolling resistance to establish the necessary horizontal load

7) use this and required tripper speed to establish power to move the tripper

Has this merit or is it a load of rubbish????

Answers on a postcard please

sir,

as you mention in point1) Not to consider the material weight. Does the rolling back of material on the inclined surface of tripper will make any difference? ■

Originally Posted by designer

Roland

The tripper is inside a building so there's one less thing to worry about

Roland & louispanjang

I thought of ignoring the mass of conveyed material because I was considering the belt complete with conveyed material to be a half of a catenary (because it's a constant weight /m belt run). In this case the only load is the catenary suspension load which would apply at the tangent point of the throw off pulley and this is based on the weight/m run of belt including material. This would also totally ignore any idler sets on the incline because there is no need for them in the worst case which is where the belt pull prior to the tripper is a maximum.

Of course not being an experienced belt conveyor designer my assumptions regarding the belt on the tripper being an unsupported catenary might be wrong, but that's where I would start for the "worst case".

Unfortunately, the request for a suitable drive unit was not accompanied by a "here's what the tripper looks like" drawing

Drive positioning

Apparently the tripper is 'long' relative to it's width so I'm going to consider a rack & pinion drive one side only.

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Greetings and saltations Designer,

In underground installations the forward and reverse switch power is carried by free sliding turnbuckles holding direct burial cable in the lower eye of the turnbuckle and all the turn buckles slide along the wire rope that is under tension and suspended at both ends by angle iron and roof bolt rock anchors holding it(the wire rope carrying and supporting the control wires in place and in line.

Anchoring a wire rope cable along the tripper line of travel is easy in a building

as long as you have steel beams near by to the line of travel.

Prior to anchoring the far end wire rope to the steel in the building you will need to slide a long turnbuckle on the cable for every 10 feet of length of the tripper belt to support the direct burial cable used to operate the winch; while this is being done the cable to power the winch is put through each lower eye of the turnbuckle and all that is needed is to simply hang it by paying out more cable than needed and run the excess wire rope through a sheave block to tension the far end using a chain come along to facilitate the bringing of the wire rope upper and lower pieces to clamp them together using wire rope clamps, a wire rope eyes for both ends and anchor it to the unused turnbuckle. at the far or near end depending on where the end of the suspension cable is anchored.

The turnbuckles used to carry the cable slide easily with the tripper and do not foul up the wire as it hangs below the eyes out of the way and it also eliminates the need for a three leg caternary as the power for the winch is at the end of the belt with the drive unit

A rack and pinion will very willingly hold dirt and dust unless it is hung under(mounted under and upside down below the tripper car.

The other problem that may pop up is the rack and pinion acting against the tripper movement if it is not centered under the tripper car from belt loading etc.

The tripper I was involved with was winch driven with a twin drum and four stationary sheaves to route the cable for forward and backward movement which was what pulled it back and forth. along a steel runway over the surge pile and steel wheels running along angle iron used for track.

There are a lot of winch powered tripper cars around and still in use, the four sheave pulleys allow a huge mechanical advantage.

Louis and I have chatted much about the good and bad of wire rope and cable winches and double drum slushers doing work etc., but as the cable is always under tension due to the double drum winch we had no problems other than salt fines build up on the rails.

The belt drive is or was a gravity take up as we had lots of height to use and take advantage of it as the tower held the belt drive and take up.

It is still working to this day after 25 years using 60 cycle 480 three phase power

lzaharis ■

Originally Posted by designer

lzaharis,

Originally the specification asked for a winch system, but our engineers were unable to find anyone to quote us

That was when I was asked for an alternative drive system, and the problems started when I asked what the drive requirement for the tripper was and got no clear answer

So I started from scratch and wrote the first post........

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The above rail line is the garden railway with snowblower to chase cats during the winter months in my corner of the Eastern wilderness @1140 feet above mean sea level.

Greetings and salutations designer-sorry about the typo-tired etc. If its not too late would you still like to see specs for a double drum winch?

send the email to:

lzaharis@lightlink.com ■

Originally Posted by designer

lzaharis,

Originally the specification asked for a winch system, but our engineers were unable to find anyone to quote us

That was when I was asked for an alternative drive system, and the problems started when I asked what the drive requirement for the tripper was and got no clear answer

So I started from scratch and wrote the first post........

dear sir:

maybe i can give your a better solution of the winch system if you can provie more infro of the system?

please contact me: zmjjohn@gmail.com ■