Plastic gear in Powrwheel mover

[Bill.D]

Has anyone had this problem. Right hand mover stopped driving, motor sounded as if it was still working so decided to strip it all down (it is a 10 year old model 3) Three steel gears on roller all ok, so looked at motor gearbox, obviously not intended to service as the gearbox halves are riveted together. Drilled out rivets and parted gearbox. Steel worm gear connected to motor shaft is ok but driven plastic gear is well worn, still engages with worm but I assume slips under load. Now my problem is that Powerwheel, unsurprisingly, do not show a spare plastic gear. Anyone had this problem and solved it without having to buy a new motor/gearbox at £150.
Bill D.

 

[otherclive]

I would look on Ebay, Gumtree, C&MHC, C&CC sites for a second hand mover assembly. You might have to buy the whole lot but that would give you two motor assemblies. Alternatively you could try a caravan breakers. Another option could be to get a small engineering outfit, or modeller to make you a pattern one, but without precise details of the gear design itself this may be expensive or a bit technically risky.

 

[Bill.D]

Thanks Clive, I am in engineering and do some model engineering as a hobby as well as caravanning (currently making a 5" gauge steam loco) so have quite a good workshop so the technicalities do not faze me. My machinery however does not run to gear cutting a worm wheel . If I can buy just the plastic gear I would be ok I think. Waiting for reply off Powrwheel to see if they can supply but am not hopeful. Your ebay suggestion is something I will explore.
Us engineers do not like to give in to replacing things that can be repaired, after all £150 for a new motor assembly makes for an extremely expensive plastic gear (probably worth a fiver).
It is sxxx law having this expense because we have decided to give up caravanning and sell the van while it still has some value (2009 Swift 535) , we are just not using it enough to justify the expense.
Bill D

 

[DrZhivago]

Steel worm gear connected to motor shaft is ok but driven plastic gear is well worn, still engages with worm but I assume slips under load. Now my problem is that Powerwheel, unsurprisingly, do not show a spare plastic gear.

Thanks for the heads-up on Powerwheel (or is that www.powrwheel.co.za ?). Using plastic for a power worm wheel? I won't be buying from them.

I would look ...for a second hand mover assembly. You might have to buy the whole lot but that would give you two motor assemblies. Alternatively you could try a caravan breakers.

Trouble is, they will probably have the same sort of wear already. Worm drives have a lot of friction in them and if transmitting any significant power they get a lot of wear unless cleverly designed, eg with steel on bronze materials and running in an oil bath.

 

[otherclive]

Steel worm gear connected to motor shaft is ok but driven plastic gear is well worn, still engages with worm but I assume slips under load. Now my problem is that Powerwheel, unsurprisingly, do not show a spare plastic gear.

Thanks for the heads-up on Powerwheel (or is that www.powrwheel.co.za ?). Using plastic for a power worm wheel? I won't be buying from them.

I would look ...for a second hand mover assembly. You might have to buy the whole lot but that would give you two motor assemblies. Alternatively you could try a caravan breakers.

Trouble is, they will probably have the same sort of wear already. Worm drives have a lot of friction in them and if transmitting any significant power they get a lot of wear unless cleverly designed, eg with steel on bronze materials and running in an oil bath.

The worn out part is not the worm gear, it is a plastic gear wheel. Having worked in the Defence sector for my whole career you might be surprised as to where you could find polymer gearwheels. 50000 ft could be one area, and well below the surface of the ocean another. Intrinsically there is nothing wrong in using polymer providing it is correctly suited for the duty cycle. And as the worn out one has had 10 years of service life I don't think its done too badly.

Buying second hand doesn't automatically mean that the equipment is worn out. Many now prefer an automatic mover so will change the older one for a newer model when they buy another van, or perhaps as they get less mobile an automatic engagement mover is attractive. So buying from someone selling a mover from say three year old caravan may in fact be a good prospect.

 

[Martin24]

If selling the van anyway I would just remove the mover and sell without it. It's not going to make a whole lot of difference to the value.

 

[Bill.D]

Thanks for reply guys. I have located a company CMR Engineering who do refurb gearbox for £60.
This includes clean, shot blast, replace bearings and other worn components, regrease.
They deal through EBay and have 100% feedback. Will probably go that route.
Although it is 10 years old, actual operating hours are very few for most people, certainly the case for us.
Will report on progress.
Bill D

 

[Bill.D]

PS agree that 'plastic' means inferior to many people, not necessarily the case, there are many high tech 'plastics'
used successfully in industry, having said that I think I would have preferred a bronze wheel, it does have to take a lot of torque.
Bill D

 

[DrZhivago]

Using plastic for a power worm wheel? I won't be buying from them.

The worn out part is not the worm gear, it is a plastic gear wheel.

I know. Strictly, that is the "worm wheel" or "worm gear". The one that looks like a screw is the "worm". https://en.wikipedia.org/wiki/Worm_drive

Having worked in the Defence sector ... you might be surprised as to where you could find polymer gearwheels. ... Intrinsically there is nothing wrong in using polymer providing it is correctly suited for the duty cycle.

Agreed, and I would not have so much issue with plastic spur grears. But as I said there is a lot of friction with worm drives which is why simple ones are less than 50% efficient, so over half the power goes into heating and grinding. For a power drive (as opposed to something like an indicator drive) I would want to see two different metals like steel on bronze, steel being for the worm as it takes more stick.

And as the worn out one has had 10 years of service life I don't think its done too badly.

I have also worked in defence, and power station, engineering and I'm used to stuff being built like ... er ... a tank. I'm not impressed with 10 years for Bill.D's mover unless he has been running it for the whole of that time :lol:

 

[KeefySher]

[
I have also worked in defence, and power station, engineering and I'm used to stuff being built like ... er ... a tank. I'm not impressed with 10 years for Bill.D's mover unless he has been running it for the whole of that time :lol:

I've worked in heavy Engineering Industries most of my life. Built like a brick shithouse, or the Ark Royal were the mantra in the early days. Contemporarily it's about commercial engineering more than proper Engineering.

The downside was lack of design for maintenance where having to dismantle a whole building to get to first motion driveshaft bearings on a 3 reduction gearbox the size of an average house was a bit expensive, moreso when same gearbox was fully dismantled and a full set of bearings and seats were changed out due to a mix up with oil samples at the NCB test lab That was the arterial run of mine coal feeding Longannet Power Station in Scotland, that for political reasons had to be kept running. and led to institutional deafness if you challenged their decisions to strip the gearbox. Still, there was massive profit on the spares and the cost of strip / rebuild.

Another industry where kit 'goes down and stays down' is in oil & gas, very expensive to recover subsea assets if they were designed by a kid on a computer game in a darkened booth

Or the worlds largest Permanent Magnet Motor that got bent when being thrown together and subsequently had no air gap between rotor and stator. The air gap should have been 7.6mm. The makers reckoned a 0.000364mm deflection on one bolt holding it to the foundation, a structure that was the largest ever single concrete pour in the UK, was the cause

Of course we are comparing Engineering to caravans, which bare no relationship to proper Engineering

 

[otherclive]

Thanks for reply guys. I have located a company CMR Engineering who do refurb gearbox for £60.
This includes clean, shot blast, replace bearings and other worn components, regrease.
They deal through EBay and have 100% feedback. Will probably go that route.
Although it is 10 years old, actual operating hours are very few for most people, certainly the case for us.
Will report on progress.
Bill D

Looks to be a useful company to know. Interested to hear how you get on.

 

[otherclive]

Keefy,

Now would that be the one that flew Phantoms and Buccaneers?

 

[KeefySher]

Keefy,

Now would that be the one that flew Phantoms and Buccaneers?

The 1st AR was well before the Wright Brothers and was made of timber so yes the one you identified. There is a ditty about ankles and ears in terms of buccaneers

 

[Bill.D]

Sent my mover off last Friday to CMR Engineering services (www.repairmymover.co.uk) had it back today (Wednesday) all nice and shiny clean, new gear and bearings, greased and assembled back together. Fitted it to motor to test run and sounds a treat.
Excellent service from Tom Dawson at CMR.
Bill D.

 

[Bill.D]

Should clarify it was just the gearbox I sent back.
Bill D