Extending vacuum cleaner hose - reduced suction?

[Blue Oval84]

Hopefully a scientician can help me understand this. I need a new hose for my Henry as the current cheap eBay one is rubbish and leaking.

Current hose is 2.4m long with 32mm diameter, apparently I can get a genuine Numatic version that is 3.9m long.

I'm aware that increasing the length of the hose can reduce suction due to friction losses, but can anyone tell me by roughly how much? If we're talking a few % I'm not worried, but as I've got one of those turbo brush heads I really can't afford to lose too much.

I've googled but to no avail. I would just buy it and see, but the genuine Numatic hose is over £30 (a new Henry is only £100!) so I don't want to buy it and then have to buy the shorter one if I lose suction.

Failing that I'm going to ask my dad to just check his Dyson on short hose vs fully extended and give me an objective assessment, but I was hoping someone knows the physics behind it!

[Buzz84]

I would have thought that it would be a miniscule amount, I'd be more worried about holes in it for loss of suction but that won't be an issue for a new hose.

The henrys we have at work have an end piece that fits onto the hose and grips it, so if you find you are having any issues with your length then you should be able to cut it down and fix the end on again

[Blue Oval84]

Buzz84 said:

I would have thought that it would be a miniscule amount, I'd be more worried about holes in it for loss of suction but that won't be an issue for a new hose.

The henrys we have at work have an end piece that fits onto the hose and grips it, so if you find you are having any issues with your length then you should be able to cut it down and fix the end on again

Yeah the current hose is so cheap that it leaks around both ends of the hose, I've had to wrap cling film around it for now which is less than ideal.

I'll ask the supplier if the 3.9m hose does that.

I did price up a Dyson V8 Absolute, but quickly decided that Henry (who must be knocking 15+ years old if not more - I inherited him) will carry on sucking until his motor gives out!

[Lotus Notes]

I've run this through a pressure drop program, knowing from experience that flexible tubing and it's high roughness factor kr (I've estimated 2mm for your case), the longer hose length gives an increase in pressure drop of 38%.

I've used a quoted flowrate of 42 l/s air for the 620W version of Henry.

I'd say that a decrease of 38% in vacuum suction is quite significant..

[Blue Oval84]

Lotus Notes said:

I've run this through a pressure drop program, knowing from experience that flexible tubing and it's high roughness factor kr (I've estimated 2mm for your case), the longer hose length gives an increase in pressure drop of 38%.

I've used a quoted flowrate of 42 l/s air for the 620W version of Henry.

I'd say that a decrease of 38% in vacuum suction is quite significant..

Seriously!?

Sod that for a game of soldiers!! Thanks for the maths!

My Henry is the much older 1200W model but allegedly the newer ones are similar flow rates to the old (if I'm honest I think mine has quite a bit more suction power than the new ones but I can't find a rating online)

So seeing as you obviously know what you're on about... Is there a hose length at which pressure drop would be more or less 100%? I just can't get my head around the physics, I assume that if say 42 litres of air are sucked out of the hose into the vacuum in one second, then 42 litres must enter at the other end, no matter whether the hose is 1 meter, or 100 meters long. Obviously I'm wrong!

And if I can make one more cheeky request, they do make a shorter hose that's 1.8m instead of 2.4m. How much extra suction do I get if I go for the shorter one?

[Lotus Notes]

Blue Oval84 said:

Is there a hose length at which pressure drop would be more or less 100%? I just can't get my head around the physics, I assume that if say 42 litres of air are sucked out of the hose into the vacuum in one second, then 42 litres must enter at the other end, no matter whether the hose is 1 meter, or 100 meters long. Obviously I'm wrong!

And if I can make one more cheeky request, they do make a shorter hose that's 1.8m instead of 2.4m. How much extra suction do I get if I go for the shorter one?

The optimum conditions is no hose..But this would be useless to you

If the hose is a lot longer, pressure drop will cause throttling and therefore the air flowrate will drop (Increasing pressure will not increase flowrate - You can only shove so many molecules down a pipe).

If the motor output is not limited, the load on the motor will increase to maintain flow, but once maximum motor output is achieved, the lack of air flow (used to cool the motor) will cause it to cut-out on thermal overload.

If the hose length is 1.8m instead of 2.4m, you'll potentially gain 18% more suction.

[Blue Oval84]

Yeah I think I follow that, in effect, if I connected something silly like a 100m hose, the air flow would be negligible and the motor would just overheat.

May give the shorter hose a shot, it'll mean dragging him around a bit more but the extra power would be good

[bristolbaron]

Brilliant. I love this place, no matter how trivial the question someone has an answer. Take 10 internet points for your efforts Mr Notes!

[Blue Oval84]

bristolbaron said:

Brilliant. I love this place, no matter how trivial the question someone has an answer. Take 10 internet points for your efforts Mr Notes!

I honestly thought I was pushing the boundaries of trivial questions, but LotusNotes has totally delivered!

[Lotus Notes]

Blue Oval84 said:

bristolbaron said:

Brilliant. I love this place, no matter how trivial the question someone has an answer. Take 10 internet points for your efforts Mr Notes!

I honestly thought I was pushing the boundaries of trivial questions, but LotusNotes has totally delivered!

Thank you, I like to contribute when I can

[TooMany2cvs]

Blue Oval84 said:

My Henry is the much older 1200W model but allegedly the newer ones are similar flow rates to the old (if I'm honest I think mine has quite a bit more suction power than the new ones but I can't find a rating online)

We've recently bought a new Henry - and it is incredibly sucky... FAR suckier than the c.15yo one we've also got. The old one's 1100w, the new one's 620w - yet the new one'll actually stick the brush end to floorboards. It's pulled a big splinter off one floorboard, and I'm sure there's a couple of nails been pulled out.

[Blue Oval84]

TooMany2cvs said:

We've recently bought a new Henry - and it is incredibly sucky... FAR suckier than the c.15yo one we've also got. The old one's 1100w, the new one's 620w - yet the new one'll actually stick the brush end to floorboards. It's pulled a big splinter off one floorboard, and I'm sure there's a couple of nails been pulled out.

My friend has a 620w model, I sense an experiment coming on in the near future.

[Lotus Notes]

Blue Oval84 said:

My friend has a 620w model, I sense an experiment coming on in the near future.

When I was a young engineer, we would quantify gaseous leaks by tying a large 300 litre waste-bin bag around the vent and timing how long it took to fully inflate the bag. From this, you could calculate the leak rate.

In this case you could fill a large bag with air and time how long it takes Henry to deflate it..Sometimes the simple things are best.

[Blue Oval84]

Lotus Notes said:

When I was a young engineer, we would quantify gaseous leaks by tying a large 300 litre waste-bin bag around the vent and timing how long it took to fully inflate the bag. From this, you could calculate the leak rate.

In this case you could fill a large bag with air and time how long it takes Henry to deflate it..Sometimes the simple things are best.

That would work, albeit I don't think I have any bags large enough.

Maybe I'll attach each one to an empty coke bottle and see which one deflates the most... Assuming two identical bottles, the one that retains most of it's shape indicates the weaker suction. Unless they just both collapse flat... Maybe coke cans.

[Buzz84]

Buzz84 said:

I would have thought that it would be a miniscule amount, I'd be more worried about holes in it for loss of suction but that won't be an issue for a new hose.

The henrys we have at work have an end piece that fits onto the hose and grips it, so if you find you are having any issues with your length then you should be able to cut it down and fix the end on again

Lotus Notes said:

I've run this through a pressure drop program, knowing from experience that flexible tubing and it's high roughness factor kr (I've estimated 2mm for your case), the longer hose length gives an increase in pressure drop of 38%.

I've used a quoted flowrate of 42 l/s air for the 620W version of Henry.

I'd say that a decrease of 38% in vacuum suction is quite significant..

Well that's me told...

though it wound be great if this can now be put into practice and tested to see how it measures up to the computer model #geekout

bristolbaron said:

Brilliant. I love this place, no matter how trivial the question someone has an answer. Take 10 internet points for your efforts Mr Notes!

Couldn't agree more - incredible place

[tim0409]

TooMany2cvs said:

We've recently bought a new Henry - and it is incredibly sucky...

We've also bought a new Henry and I am finding it quite difficult to use on carpet as the suction is so strong (the carpet pile isn't even that deep). I have read that they suggest a "turbo" head? My wife isn't that impressed with it, but it will be great for cars......

[Toltec]

Blue Oval84 said:

TooMany2cvs said:

We've recently bought a new Henry - and it is incredibly sucky... FAR suckier than the c.15yo one we've also got. The old one's 1100w, the new one's 620w - yet the new one'll actually stick the brush end to floorboards. It's pulled a big splinter off one floorboard, and I'm sure there's a couple of nails been pulled out.

My friend has a 620w model, I sense an experiment coming on in the near future.

A more efficient fan and air path design, while it is easy to moan at the EU for setting limits for vacuum cleaner power consumption in this case they might be right. The manufacturers have just marketed cleaners on having more powerful motors, now they have to make them efficient to sell them.

I look forward to reading the results of your experiment

[C&C]

Blue Oval84 said:

Lotus Notes said:

When I was a young engineer, we would quantify gaseous leaks by tying a large 300 litre waste-bin bag around the vent and timing how long it took to fully inflate the bag. From this, you could calculate the leak rate.

In this case you could fill a large bag with air and time how long it takes Henry to deflate it..Sometimes the simple things are best.

That would work, albeit I don't think I have any bags large enough.

Maybe I'll attach each one to an empty coke bottle and see which one deflates the most... Assuming two identical bottles, the one that retains most of it's shape indicates the weaker suction. Unless they just both collapse flat... Maybe coke cans.

Another possible alternative - you could get a smooth ball - e.g. kids plastic football and put the 2 hoses on opposite sides so they suck themselves onto the ball. then pull them apart and see which one comes away with the ball - the weaker one being the one that ends up without the ball.

[TooMany2cvs]

Toltec said:

A more efficient fan and air path design, while it is easy to moan at the EU for setting limits for vacuum cleaner power consumption in this case they might be right. The manufacturers have just marketed cleaners on having more powerful motors, now they have to make them efficient to sell them.

Hush with your facts and reality!

[Blue Oval84]

tim0409 said:

We've also bought a new Henry and I am finding it quite difficult to use on carpet as the suction is so strong (the carpet pile isn't even that deep). I have read that they suggest a "turbo" head? My wife isn't that impressed with it, but it will be great for cars......

Genuine-
http://www.ebay.co.uk/itm/Genune-Henry-Hetty-Numat...

Pattern-
http://www.ebay.co.uk/itm/Red-Tool-For-A-Henry-Het...

For the car-
http://www.ebay.co.uk/itm/Vacuum-Turbo-Floor-Brush...

You can thank me later

The little one makes doing the car carpets so much easier and the big ones are a lot easier to push about than the non-turbo version.

ETA - when using the little one, the rubber "teeth" retract out of the way when you're just wanting to whizz it over the carpets without trying to extract pet hair.

Edited by Blue Oval84 on Thursday 10th August 21:30