What is this thing?

[deema]

It’s a bit ambiguous title, but I can’t seem to find the right words to describe it to google a replacement. It’s a two way spring strut I think? It comes off a GreenMachine 400 series road sweeper and it’s no longer springy. I suspect it’s the same thing that motor bikes use for their suspension?

Anyway, if anyone can point me in the right direction yoi would have my thanks.

I bent the eye trying to free it up and get it moving again……grrrr it is solid.

 

[Jacob]

Gas strut?

 

[flying haggis]

what is usualy called a shock absorber but is most usually used as a damper to stop springs bouncing

e-mail them and ask

Email: [email protected], [email protected]

 

[deema]

Thanks, it’s not a shock absorber, there is a gas strut ahead of it that carry’s out this function. This is the main rear suspension and the manual description is that it’s a two way spring strut. Now tried googling that and all I’m getting is gas struts.

 

[Sideways]

Motorcycles typically use a coil spring wrapped around a shock absorber cylinder. One unit each side when they have proportions like yours.

The reference to twin spring could mean two springs in series. A soft one and a hard one to give a compliant ride plus resistance to bottoming out on big hits. That's not unheard of. The springs on bike shocks are often on display but in a sweeper, enclosed might last longer.

Alternatively:
Imagining a "piston" inside that cylinder and a coil spring on each side of that, that would give a spring unit that naturally centres and works in both tension and compression. I've no idea if such a thing exists and what it would be called. Does that configuration make any sense in your machine ?

Is the weight of the machine riding on this and the one on the other side, or is it involved in the ride height of just the sweeper mechanism ?

 

[ChaiLatte]

Is the weight of the machine riding on this and the one on the other side, or is it involved in the ride height of just the sweeper mechanism ?

That is a good point. We could maybe find out what a good name for it would be by determining its function.

It is also plausible that it is just like an inside-out motorbike twin shock.

In very simple terms, what happens when it is removed? Does the suspension collapse so the machine rests on the bump stops? Does the machine remain suspended but bounce all over the place when it hits a bump?

If it is truly beyond repair, cut it open and see how it works.

 

[Amplidyne]

Stupid question I will guess, but don't the company supply spares?
If it's "just" acting as a spring, and doesn't any longer, then I'd suspect it's some kind of gas strut. Never seen anything quite like it though. Custom made part?

 

[ChaiLatte]

I think there is a parts manual here:

http://d2z4qs2e3spnc1.cloudfront.net/product_file/file/526/400_green_machine_parts_manual.pdf

Item 24 on page 15 and oddly enough item 25 on page 16 (and not on page 54 at all). It is also item 5 on pages 55 & 56. The MA571 number appears here (https://shop.usaclean.com/2-way-spring-strut-assembly-tennant-industrial-475-7136/) and is a bargain at $944.39 plus shipping.

 

[Tris]

If you have no luck with greenmachines it might be worth emailing SGS engineering with a pic and description. They have been very helpful in the past when I've been looking for an odd spring or strut

 

[Amplidyne]

Wonder if it's not a standard gas strut with a fabricated cover over it for some reason?

 

[Fergie 307]

You can get gas springs, maybe that is what it is.
You could try these in Bedford. [email protected].
They are manufacturers of all sorts of gas struts.

 

[deema]

Thanks everyone. I had written to Greenmachines for a quote, which has come back and it’s £225 including carriage and VAT. Thats a bit eye watering considering I only paid £400 for the whole machine

I think it is a gas spring, probably two springs holding the piston in the centre I suspect. I was wary about taking it apart due to releasing an unknown spring energy. But, I am going to very cautiously have a go. The end cap looks to be cast aluminium into a steel tube, so low chance of that unscrewing!

 

[Sideways]

If it is gas, it won't be serviceable - at least for any sensible price ? - so you could carefully drill say a 2mm hole maybe 30mm in from one end, and then the other and see what if anything comes out.
That would be less dangerous than me when I was a kid and put a sparklets CO2 bulb in my dad's vice and whacked a nail into the end. Whoosh ! And a hole in the slate roof of the outhouse.

 

[Fergie 307]

If it is gas, it won't be serviceable - at least for any sensible price ? - so you could carefully drill say a 2mm hole maybe 30mm in from one end, and then the other and see what if anything comes out.
That would be less dangerous than me when I was a kid and put a sparklets CO2 bulb in my dad's vice and whacked a nail into the end. Whoosh ! And a hole in the slate roof of the outhouse.

I think I am correct in saying that we're actually invented by Crosman in the USA for powering air, or more correctly Co2, powered guns. About 800psi.

 

[Fergie 307]

Thanks everyone. I had written to Greenmachines for a quote, which has come back and it’s £225 including carriage and VAT. Thats a bit eye watering considering I only paid £400 for the whole machine

I think it is a gas spring, probably two springs holding the piston in the centre I suspect. I was wary about taking it apart due to releasing an unknown spring energy. But, I am going to very cautiously have a go. The end cap looks to be cast aluminium into a steel tube, so low chance of that unscrewing!

Worth building some kind of restraint that will hold it while you try and undo the end.
I would be very careful. If it is a gas spring then the internal pressure is likely to be in the region of 700-1000psi.
Having said that the case looks to be a bit of thin tube with a welded seam. Gas springs usually have a thicker CDS tube.

 

[deema]

If it were a gas spring, wouldn’t there be some kind of nipple to allow it to be charge with gas when manufactured? This only has the screwed in end cap and no way of charging the unit with air.

 

[Fergie 307]

Sometimes the cap is just in effect a holder for the rod seal, and to keep muck out. Once removed there might be another cap underneath.
But if the tube is the thin wall welded seam type, then unlikely to be filled with anything at high pressure. Difficult to tell from the pictures.
Even if it does just contain a regular metal coil spring, undoing the collar might be enough to free whatever is jamming it. It could then come out with some force.
I would certainly restrain it in some way. Even some poly rope through the eyes to stop it expanding unexpectedly.
I have a full set of BMW motorcycle tools, one of which is essentially a pillar type car screw jack with interchangeable yokes that would fit the eyes or over the ends of the unit. This is what we used to use to compress the various types of suspension units while the retainers were undone, and to then release them in a controlled way. Still use it on bikes. I have a much bigger hydraulic one for cars.
You really don't want to be in the way if one gets free, even quite small units pack quite a lot of energy.

 

[Fergie 307]

It might be worth sending some images and dimensions to the firm I mentioned in Bedford.
I doubt it is actually manufactured by the sweeper people, it may be an off the shelf part. The folk at Bedford may well recognise it and be able to tell you who the actual manufacturer is, or have an equivalent.
Safe bet it will be a lot cheaper direct from whoever actually makes it.
The other thing would be a trailer specialist, some of them use gas suspension struts, basically just a bigger version of the ones that open the tailgate on many cars. From your description it looks like that is what it is. They might be able to supply something suitable.

 

[deema]

@Fergie 307 Thank you do much for you insights, it’s really appreciated. The quote adds a bit more info, it’s made in Macedonia.
I will give the guys you suggest a call tomorrow.