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Threadless control box

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Threadless control box

Postby Jimmy Mack » 11 Nov 2016, 15:20

As mentioned on a previous topic (I'm fixing up an old SCM si150).

The two button control box has a bit of an issue.... the existing face plate is hanging off! The housing/ back box is metal and the integrated threads are completely gone on the right h/s ...

I've a couple of options:

Tap out the threads up a size (I don't have a tap set)...
Buy a new box
Find a fix trick... perhaps glue in a nut?

The twist release has gone on the emergency stop also, I'll have to see what that's doing when we get power, as it may not even work/ be an issue.

Jim

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Re: Threadless control box

Postby Jimmy Mack » 11 Nov 2016, 15:21

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Re: Threadless control box

Postby 9fingers » 11 Nov 2016, 15:54

You could try gluing in a nut but it is an awful bodge solution. Grease the screw you use to hold the nut in place to save gluing it in place too!

or drill right through the box and out the back and fit longer screws with nut and washers on the back.

lots of ebay vendors selling individual or small packs of nuts and bolts.

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Re: Threadless control box

Postby Jimmy Mack » 11 Nov 2016, 17:42

Thanks Bob.

Yes, I agree, gluing the nut in would be a bodge, too much torque and they could fail and I'd be locked out!

Not sure if you can make it out, but the two black tips on the bottom of the box are screws which go right through the box holding it in place, these block off screwing right through, as they are in line ...nice idea though.

However I don't see why these can't be shortened...I guess this was done to make installation easier.

Jim


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Re: Threadless control box

Postby 9fingers » 11 Nov 2016, 18:04

You could always discard the box and use the same mounts to fix a piece of angle iron/aluminium and onto that, fix a new push button station. There are several ebay suppliers doing ready built units with a variety of switches fitted.

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Re: Threadless control box

Postby Tusses » 11 Nov 2016, 18:05

Long time since I looked at them, but can you get "riv nuts" that size ?
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Re: Threadless control box

Postby 9fingers » 11 Nov 2016, 18:09

Tusses wrote:Long time since I looked at them, but can you get "riv nuts" that size ?



I wondered about that but there would be very little meat if any to mount it and likely to crack the box.
Helicoils would do too but the OP does not even have stand taps let alone oversize helicoil taps.

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Re: Threadless control box

Postby Tusses » 11 Nov 2016, 20:35

ok then .... :lol:

"(I'm fixing up an old SCM si150)."

anyone that is fixing up things has the perfect excuse to buy a new toy, like a tap and die set !
They're not expensive (one of your options was a new box ! ) , and will prove useful over an over :)
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Re: Threadless control box

Postby Robert » 11 Nov 2016, 23:11

I'd forget the existing holes and drill one new one half way between them then fit a self tapper screw. job done.
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Re: Threadless control box

Postby DaveL » 12 Nov 2016, 00:10

Robert wrote:I'd forget the existing holes and drill one new one half way between them then fit a self tapper screw. job done.

I think the box has thin sides with the corners filled in to give enough metal to be drilled and tapped.
Buy a set of taps and the fill the striped holes with car body filer, then redrill and tap them, would be my solution.
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Re: Threadless control box

Postby Jimmy Mack » 12 Nov 2016, 15:30

DaveL wrote:
Robert wrote:I'd forget the existing holes and drill one new one half way between them then fit a self tapper screw. job done.

I think the box has thin sides with the corners filled in to give enough metal to be drilled and tapped.
Buy a set of taps and the fill the striped holes with car body filer, then redrill and tap them, would be my solution.


Yes, Dave's right there with the box description, I should of opened it up for a picture.

I think I'll wait till my sparks pops over next week and see how she's running. Managed to get my head in on the back of the motor to snap the spec plate (the dealer I bought it off thought it was the standard 3.3KW ,4hp model...

:o :o mother?! :shock:
Last edited by Jimmy Mack on 12 Nov 2016, 15:33, edited 2 times in total.
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Re: Threadless control box

Postby Jimmy Mack » 12 Nov 2016, 15:32

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Re: Threadless control box

Postby 9fingers » 12 Nov 2016, 15:36

Woo hoo 7.5 horses under the table eh? Proper job!!

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Re: Threadless control box

Postby Jimmy Mack » 12 Nov 2016, 15:38

9fingers wrote:Woo hoo 7.5 horses under the table eh? Proper job!!

Bob


Best not turn it on n off too much... :lol:

Bob, while you're on... Are those the Start up Amps and FLA figures?

19/ 11
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Re: Threadless control box

Postby Jimmy Mack » 12 Nov 2016, 15:43

...actually thinking about it.. a 19A Start up seems too low...I'd expect something in the mid 30's

:eusa-think:

I'll fish about in the schematic book
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Re: Threadless control box

Postby 9fingers » 12 Nov 2016, 16:02

No those all fla running currents. Quite a bit more for starting inrush. Make sure you fit type c mcbs in your fuse board to avoid nuisance trips on start up. There are soft start solutions if you get desperate but cost!!!

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Re: Threadless control box

Postby Jimmy Mack » 12 Nov 2016, 16:28

9fingers wrote:No those all fla running currents. Quite a bit more for starting inrush. Make sure you fit type c mcbs in your fuse board to avoid nuisance trips on start up. There are soft start solutions if you get desperate but cost!!!

Bob



Ah ...Thanks Bob, I have some c Curve 16A MCB's

I'm still a bit in shock, (no pun intended)...RIPPING will be an absolute breeze :eusa-dance: not sure about my electric bill tho :shock:

Still, SWIMBO's got some pretty mean hairdryers :D
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Re: Threadless control box

Postby 9fingers » 12 Nov 2016, 17:00

When you taking power factor of a less than fully loaded motor into account then running costs are small.
The current and voltage are well out of phase.
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Re: Threadless control box

Postby Jimmy Mack » 12 Nov 2016, 20:52

Kinda like motorway driving... Bigger engine and bigger the wheels ( blade ) the more energy it can store and less likely under load therefore less consumption ?

Pushing a few amps on start up to meet the inital resistance?

That's my logic...probably talking rubbish though

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Re: Threadless control box

Postby Jimmy Mack » 12 Nov 2016, 20:56

...town driving won't be too hot

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Re: Threadless control box

Postby 9fingers » 12 Nov 2016, 21:39

Not really a good analogy

Just keeping a blade spinning takes very little power. Feeding lumps of wood through absorbs lots of power and it is power that you pay for.

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Re: Threadless control box

Postby Jimmy Mack » 13 Nov 2016, 10:22

9fingers wrote:Not really a good analogy

Just keep a blade spinning takes very little power. Feeding lumps of wood through absorbs lots of power and it is power that you pay for.

Bob

My understanding is a little sketchy.

More current drawn under load to maintain rpm(?) makes sense, but what makes the initial current pull higher?...is it the initial resistance of the motor mass, the amount of coil or both?

Is the KW rating the max potential under (heavy) load Work and start up, with a lower KW in idle/ low load as the potential different between amps and voltage is lower in this state?

Probably talking gobble de goop and confusing myself ...could do with some further reading . I guess what I'm trying to understand are the pros and cons of a bigger motor

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Re: Threadless control box

Postby 9fingers » 13 Nov 2016, 12:23

Bit too much of a complex subject to deal with in a thread but I hope this might help.

When running, a motor also acts as a generator and will always generate a voltage in opposition to the applied voltage. This is often called back emf. This reduces the current when it is rotating compared to the stationary current when it first starts up.

The power you pay for (in a domestic leccy meter) = voltage * current * power factor (0>pf>1)

When the load on the motor in minimal, the pf is low. What power is consumed is used to drive the fan, overcome friction in bearing and belts and heat up the motor windings due to their resistance.

Under high load the current goes up a bit but it is the power factor that approaches unity and so the power you pay for goes up but only when the machine is working hard.

When the motor is overloaded, it can no longer maintain its speed. So the generator effect is less, the back emf starts dropping and the current rises above the full load current, generates lots more heat, fan cooling drops off and soon the magic smoke appears and the motor insulation breaks down etc etc.

What might be difficult to understand is that the current drawn under light load is still relatively high maybe half that of full load but it is the power factor which varies more with load.

Pros and cons of a larger motor? mainly pros is terms of capability, deep ripping etc and in normal use, staying well away from the overload point. Cons? slightly higher idle power consumption but that is about it.

Hope this helps

Bob
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Re: Threadless control box

Postby RogerS » 13 Nov 2016, 12:33

Interesting explanation, thanks, Bob. Why does the power factor alter as load is applied ?
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Re: Threadless control box

Postby Andyp » 13 Nov 2016, 12:40

If all else fails could you glue a piece of wood behind the holes in the box and then use screws to hold the front on?
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