WW1 Thornycroft restoration

[8_10 Brass Cleaner]

Tony, I was interested to read about sandblasting and loss of the interference fit between rim and tyre. We were talking about this very thing last weekend. Is there a way of measuring outer rim -v- inside tyre to ensure the "perfect interference fit"? How was this done in days gone by? Robert

 

Having recently read a book on Marsons Road Services and some of the men involved it seems that on the Scammell 100 tonner they had problems with the wheel revolving within the tyre when working hard. They solved it by pressing the wheels on with rubber fire hose between the two.

 

I've just aquired some solid rubber tyres that have come off a steam wagon because they were loose. They are bored out tank road wheels and are slightly oversize for a 670mm wheel. I intend using an adhesive between the rubber backing and the cast wheel of my trailer.

 

another option with a loose wheel and one I have thought about it to use a Sal-Ammoniac paste. Basically a mixture of sulphur, iron and urine, the mixture causes quick corrosion and thus used in boilermaking to seal.

 

The way it works is iron oxide is expansive so the boiler seals as it rusts. I wondered if this would work on a loose tyre. The trouble is with my tyres is as they are bored out tank road wheels there isnt a continuous plate, its ribbed. However with a proper smooth backing on a press on tyre I would have thought it would work well.

[Minesweeper]

I think that you can be as technical as you would like to be in trying to work out a precise interference fit - I am no Mathematician or professional engineer - but I think that there are certain guidelines that we have learned from the more experienced in this particular field. I wonder if a precise properly calculated interference fit would actually work where you are mainly not dealing with clean, regular and smooth surfaces.

 

Rust seems to be the answer in keeping a tyre tight on a wheel. This was the mistake that we made when fitting the Dennis rear wheels. Those wheels were sand blasted after the old tyres were taken off and the original tyre bands to be used again for the new tyres, were also sand blasted. So when the new tyres on the old bands were offered up to the wheels, they just dropped loosely down on the wheels and could be rotated by hand on the wheels. So all the original interference fit had been destroyed in the sand blasting of the two mating surfaces.

 

To keep the tyres tight on the wheels, we had to insert a steel shim between the two all the way around - but that was found to be insufficient on its own so a wet canvas was also used to fill the final space. Wet so that it would cause the wheels and tyre bands to rust together as quickly as possible. Those tyres have not moved on the wheels.

 

Quite by co-incidence, I was speaking to our friend Barry W on the telephone this morning about another matter and I mentioned this "Old Chestnut" to him which had cropped up again. He told me that only very recently, another friend had come to him to make use of his tyre press. His wheels were first sand blasted with the old tyres left on to protect the rim from the sand blasting- the old tyres were then pressed off and brand new old stock tyres were pressed on and they went on as a perfect fit.

 

So although we like cleanliness, sand blast wheel rims and tyres at your peril!

 

Tony

[Great War truck]

We will have to begin to think about body style for the Thornycroft soon.

What do you make of this one? Sliding windows would be quite useful.

 

[Redherring]

The London Transport Museum has a lovely picture of a London-bus tyre-storage garage. Surrounded by new tyres are two blokes with a hammer who look like they're in the process of gently tapping a new tyre onto a wheel rim. There's no press in sight. So is it reasonable to assume that a new tyre was a perfect fit for an old rim and that perhaps they added water when all was in place?

Robert

[Redherring]

Found the link to the photo... london transport museum / collections / tyres...

 

http://www.ltmcollection.org/photos/photo/photo.html?_IXSR_=KRag4gXmoTE&_IXMAXHITS_=1&IXinv=1998/87504&IXsummary=results/results&IXsearch=tyres&_IXFIRST_=4

[Roy Larkin]

We will have to begin to think about body style for the Thornycroft soon.

What do you make of this one? Sliding windows would be quite useful.

 

 

I prefer this one - just need a slice from an old railway carriage and the jobs done. Might even get a nicely upholstered seat as well.

 

[mammoth]

Vulcanising new rubber onto a tyre band involves considerable heat and that may have been responsible for expansion of the old rim. In respect of steel tyred (horse) carts every blacksmith (here in Australia) had a tyre shrinking machine to deal with both shrinking timber wheels but also the effect of tyres growing and coming loose with the pounding on gravel roads.

Edited April 8, 2014 by mammoth

[Minesweeper]

Vulcanising new rubber onto a tyre band involves considerable heat and that may have been responsible for expansion of the old. rim

 

The new Dennis Tyres on the old bands were not of rubber but of polyurethane - I really do not know how they do that but I guess heat is involved with that as well?

 

Tony

[Roy Larkin]

Having recently read a book on Marsons Road Services and some of the men involved it seems that on the Scammell 100 tonner they had problems with the wheel revolving within the tyre when working hard. They solved it by pressing the wheels on with rubber fire hose between the two.

 

 

 

 

Indeed they did. They bought worn out fire hoses from Liverpool Fire Brigade for the purpose. Cut them into narrow strips and put them between wheel rim and tyre as the new tyre was pressed on.

 

There are reports of lorries being unusable for weeks at a time in France while waiting for the correct size tyres to become available and then within a matter of hours of new tyres being fitted were unusable again as they tyres were falling off, so the problem isn't anything new.

 

Just how many tyre sizes were there? How universal are/were they? I'd assumed a relatively small number of tyre sizes that would fit the wheels on any make of lorry but it seems that's not the case as there were times when tyres for Halleys were impossible to obtain and when they were obtainable, another make such as Daimler or Thornycroft were devoid of tyres as they became unobtainable. I appreciate that Halley wheels wouldn't fit a Daimler, or vice versa, but would have thought that tyres for Daimler wheels would fit Halley wheels etc.

[MatchFuzee]

If there is sufficient metal in the wheel rim have you thought of machining the rim down to a clean surface then fitting a steel tyre as is done to railway wheels to produce the correct diameter for the rubber tyre?

 

This link describes the method:-

 

http://en.wikipedia.org/wiki/Train_wheel#Tire_installation

 

I would question if leaving the rust to hold the tyres in place is really a solution to the problem, because as the vehicle is used won't the rust break up and eventually work it's way out, leading to loose tyres?

[flandersflyer]

i suppose a good way of getting over problems such as this would be to utilise something similar to a pipe/tube expander...but on a much larger scale....

 

this could be fitted inside a slightly undersized tyre...but in such a way as that the edge of the tyre could be dropped over the wheel...the tyre expander could then be released...and then re-applied further towards the edge of the tyre....and so the process could be repeated to kind of `inch` the tyre onto the wheel...

 

it would then be on tight enough i`d say...

[andypugh]

I reckon metal-spraying would be another solution, though possibly a bit expensive.

 

I recall using a special-purpose water-hydraulic solid tyre press several years ago (belonging to an old-truck man, but I can't recall the name.) It did the job it was built for very well. Strangely enough.

Last I heard I think that press was looking for a new home. I imagine it found one.

[Asciidv]

I am having the wooden wheels from my 1914 Dennis re-hooped. The plan is to have oversize hoops made and then turn the hoops to size when on the wheel. The hubs will be fitted and everthing will be turned with respect to a shaft running through the hub. This will ensure that the wheel assembly is truly round and that I can obtain the correct interference fit for the tyre band.

 

Some things concern me. First I doubt if the tyre band is very round as it will have just been ring rolled and welded up so all the precision making the wheel round will have been wasted! Secondly no-one yet has has been brave enough to say how much oversize the wheel should be. I wonder what was the original specification? Incidentally I did think that the pi-tape that Andy suggested was ideal for this work so it is now winging its way towards me. If anyone wants to borrow it, just ask. I already have a suitable bore gauge so the metre long digital vernier calipers will not be necessary!

 

However, all the time, I come back to thinking that the wheels were put together 100 years ago by blacksmiths who were more use to cart wheels, so surely we can get it right today.

 

(Just as final note, my hoops had been loose in the tyre band so someone in the past just seam welded them in. I spent weeks and weeks with a hacksaw blade cutting them out).

 

 

 

Barry.

Edited April 10, 2014 by Asciidv

[Barney]

I understood that wooden wheels had steel tyres shrunk on in order to tighten the joints in the fellows and spokes to provide a rigid wheel;is this not the case with artillery style wheels?

 

With old tyres does the rust build up on the rim stretch the tyre over time; hence the reason that they are loose when refitted on grit blasted rims?

John

[Charawacky]

From my own experience the concentricity of a new wheel can be very good.

These wheel run up to 45 mph with out problem which is substantially in excess of a solid tyre vehicle.

 

If you are looking for advice the wheelwright who made these would be worth talking to, please send a message and I can send his contact details. He was the last time served wheelwright working, built wheels for the royal carriages and has retired now.

[Tanker Wannabe]

I was wondering if a travelerer, as used with wooden wagon wheels could have been used. They had been around for some time so they would have been known.

http://www.antiquetools.com/10-tools/10-Tools/traveler.html :???

[Minesweeper]

We took the front axle down to our local garage today so that we could make use of their Hydraulic Press. We wanted to get the front axle stripped down as really the next step in getting the front end of the lorry together is to hang the axle on to the springs.

 

The Press was required to take the King Pins out – everything was so rusty and corroded and we anticipated great trouble in getting them to move – but we had been dosing them with Plus Gas over a period and much to our surprise – and also great pleasure, very little effort was needed to get them moving! Again Plus Gas has made life easier!

 

It seems that every time that we do something fresh on the lorry, we meet with a surprise or two – and again this was no exception. We knew that one of the King Pins was revolving in its housing when it should have been fixed with a pin going half way through its supporting fork and half way through the King Pin so we expected to see wear at that point.

 

The surprise was that there were two “channels” in the King Pins – one above the other – where the securing pin was meant to hold it. The King Pin appears to be of a standard Thorny J pattern and the only reason we can think of for the second groove is that the King Pin had been fitted in another axle before – the grooves had not lined up in the second .fitting so a fresh one had been cut in each of the two pins to suit their second use.

 

No firm decision has been made but it rather looks as if we shall have to make new King Pins.

 

[GeePig]

I am surprised that the king pins are the same as another model except for the groove for the retaining pin. Why would they change the position?

 

Whatever, do you think there is a chance they simply bought the wrong king pins new?

 

trevor

[Barney]

Possibly replaced in service with whatever was in stock at the time and adapted to fit; remember there was a war on.

John

[David Herbert]

It's nice that they came out without too much of a fight.

 

Is it possible that these are not actual Thornycroft king pins but replica ones? The army depots in France seemed to be able to make all sorts of parts so I would have thought that king pins would have been very simple. There would then have been at least another thirty years when making these sort of parts would have been regarded as normal. The two location groves could simply be a mistake.

 

I think that you will probably be making nice shiny new ones in a much better grade of steel than was available then.

 

David

[Minesweeper]

Another good day of progress – at least moving forward in the right direction!

 

We have had a look at the two stub axles released from the main body of the front axle and find that not surprisingly, they are bushed! The top bush is a little unusual – at least unusual to us as it incorporates the lower half of a thrust bearing. The top part of the bearing was taken off much earlier and the very rusty balls came with it. We firstly assumed that the lower part of a standard thrust bearing was stuck or corroded to the top of the stub axle but find now that it is one part of the actual bush. It is unfit to be used again.

 

So both bushes have now been pushed out. We have never seen thrust bearings made up in this form and if they are no longer available then we shall have to think out and plan the way ahead!

 

Perhaps Chris G would like to come in here with his professional knowledge of bearings and comment on them – and perhaps say that (hopefully) that type are still available.

 

With the King Pins looking a bit sad, we are considering putting them through a Rotary Grinder to reduce the diameter by a just a few thous’ and then making new bushes for the stub axles slightly smaller accordingly to fit the reduced size.

 

 

 

 

 

[Minesweeper]

The front wheels and front axle came back from the Sand Blaster yesterday – the wheels were heavily rusted and it could not have been easy for them to get inside the front plate to get all of the rust out. However, they did a good job!

 

We have agreed now that we will have the hubs skimmed/bored out to get rid of the wear and to bring the bores back to a smooth and true finish again. But to make life easier for the machinist who will do this for us, we wanted to clean them up first of all. They will be primed before they leave us to keep any rust at bay.

 

As with the sand blasting, it is not easy to get inside the front plate to paint it – but Bonda Primer, our favourite primer also produce their primer in aerosols, and this seemed to be the answer to get it inside that front plate. In fact, it worked admirably and that then just left us to paint the outside front at the rear plates with a paint brush in the usual way.

 

[Chrisg]

Easy answer is no. But a three piece thrust bearing (2 washers & row of balls in a cage ) depending on sizes should be available you would need to turn or grind the old one of the bush then fit the new one

[David Herbert]

Surely what Thornycroft were trying to do with their one piece top bush and thrust bearing was to use the thrust bearing to take normal transverse loads as well as all the vertical load - sort of the opposite to a normal ball bearing which is able to take limited axial loads.

 

Any large transverse loads would be taken by the plain part of the bush but that could have been designed to have a slight clearance normally which would noticably lighten the steering. Any shock load would simply make the balls of the thrust race climb their groves untill the kingpin contacted the inside of the top bush - you would only need say 5 thou clearance which would not hurt either the thrust bearing or the bottom bush. A pure thrust bearing has much shallower tracks for the balls as it is not intended to take side thrust at all.

 

I wonder if it would be possible to re machine the old thrust races and use a size bigger balls. It is only turning very slowly after all.

 

David

[alixcompo]

Could the king pin location groove be the result of the easiest mistake.?

Insert the pin to mark the groove position forgetting that it drifts further into place on final assembly.........