Hooben T55

[forgebear]

hi pete this is great makes me want to start mine now but i have a lot on the go at the mo so will have to wait but great reading
thanks dave

[BigPanzer]

Hi Dave,

Thanks Dave. Not much to report as I'm waiting for the bearings to arrive. I've started on the plastic bits for the hull top. Doesn't go together as well as a Tam, but not difficult so far. Bits of flash to clean off, quite a few sink holes on some of the smaller components will need filling, other little bits of fettling and so forth, but really not too bad.

More woffle later.

Peter

[rshermanking]

hi guys this what got done so far with mine

rshermanking


sorry guys having trouble up loading pics will try later when i can get it sorted, but if you can go to the other furom across the pond you can see them there.


rshermanking

[BigPanzer]

Hi everybody,

Thanks for sticking your head up Rshermanking - it was getting awfully lonely here. How are you finding the build? I'm finding all sorts of small niggles, but nothing really serious and I'm quite enjoying the build so far.

I must apologise to all here about my absence for the last few days - domestic issues have kept me away from my workbench, but the newly redecorated bathroom is now complete. 'Er in drawers is now happy, which means I am free to play for a while.

Look carefully at the sprockets. You will find that they can be fitted together more than one way, but only in one position will the teeth line up correctly. Because there is play in the dogs cast into the sprockets I glued them together with epoxy, but you still have to check carefully that the teeth line up properly. I used a straight edge across the teeth and a length of track to make sure the alignment was perfect.

The next stage I attempted was fitting the gearboxes and sprockets, and once again I found things that could be improved. I was delighted to see that Hooben fit a pair of needle roller bearings in proper, but plastic drive housings though as usual things need fettling. But first a few words about needle roller bearings.

Once fitted these bearings are capable of high speeds and high lateral loading but they can be fragile and are easily damaged. First of all they need to be very clean. Swill them out well with some thinners or petrol and you will be amazed at the amount of crap that comes out of them.
Never force them into the cups in the housings. If you do you can distort them slightly and then they are useless. Do NOT use a vice to press them home if they are tight. Enlarge the cups slightly with a round file until the bearings can be pressed home with nothing more than finger pressure. Being brutal here can damage not only the bearings, it can also damage the cups in the housings.
Once you are happy with the fit, clean the brass sprocket shafts, put a drop of 3 in 1 or similar inside the bearings and try the shafts in the bearings. Try not to scratch the surface of the shafts. If they feel a bit tight or rough then the shafts can be smoothed with some fine wet & dry (used dry). Work round the shafts, not up and down them.
Once everything is running smoothly, insert the screws which fix the brass extension shafts to the gearbox output shafts, but do not assemble them permanantly at this stage.

Now to the gearboxes. These are held in by eight screws, but Hooben do not provide or suggest washers so I had to dig in my spares box. You will need seven of them.
One screw goes through the moulded access panel on the underside of the tank. Hooben provide a countersunk screw for this position, but the hole is not countersunk! Throw this screw into your spares box and find either a dome head or cheese head screw that will fit.
Fit the gearboxes, making sure that they are correctly seated in the hull, but only lightly tighten the screws.
Check that the gearbox output shaft is central in the hole in the hull. One was fine but I had to tickle the hole on the other one lightly with a half round file to get the other one properly concentric.
Check that the hull does not twist when the gearboxes are screwed in.

Now fit the drive housing together with the temporarily assembled sprockets and extension shafts. You will need to remove the screw which fixes the rear of the rearmost torsion block on the left side of the hull. The hull is assymetric so the one on the right hand side is fine.
Check that the end of the bearing cup in the housing fits into the hole in the hull properly. I filed a small lead (bevel) on the end of the cups to make the fit easier.
Check also that it is possible to get adjustment for width over the sprockets. A length of track is useful here.

Take everything apart and remove the gearboxes. You now have plenty of practice putting the bits together, you know everything fits perfectly so you are ready for final assembly, which has to be done quickly.

If you read my previous scribblings re: gearboxes you may recall that the bearings on the gearbox output shafts were fitted in over sized holes and required locktiting in place. Now is the time to apply it. I did it on the inside of the gearboxes, where there is a flange. Push the bearings back about 0.5mm, apply a drop of locktite then push the bearings back against the gearbox side plate. Before this locktite fully cures you need to complete the entire assembly. Screw the gearboxes back in place, again leaving the screws slightly loose.
Next fit the housings, (checking the needle bearings are properly oiled) complete with the needle bearings and extension shafts. Do not fully tighten the set screws.
Fit the previously assembled sprockets, fully tighten their securing screws, but do not locktite them in place - you will need to get them off for painting.


Now you need to remove the set screws in the extension shafts one at a time and put a drop of locktite in the holes. Do not tighten them yet.

Adjust the position of the sprockets so that there is clearance between the inside edges of the tracks and the moulded in bolt heads on the outside of the drive housings.

When you are happy that the clearance is correct you have eight gearbox screws and the four shaft set screws to gradually tighten up. Do each screw a bit at a time until they are all fully tight. With luck you can do all this before the threadlock on the gearbox bearings has cured, so the output shaft, extension shaft and housing should settle into their "best" position. The last job is to glue the housings in place, pushing them fully against the hull sides as you do so. If you want to be really fussy (like me) you can connect up your gearbox test rig (the 1.5v battery with the wires soldered on) so the housings will settle in their "best" location as you apply the glue.

So there you are. Gearboxes and sprockets fitted, with good alignment, free running, well supported shafts and minimal end float! I was also surprised how rigid the hull had become once everything had been fully tightened.

Thats all for this stage. In the next episode I will be modifying and fitting the road wheels, then the idlers.

Peter

[rshermanking]

rght lets try again rshermanking


G]G]

[rshermanking]

[rshermanking]

[rshermanking]

i hate computers sorry about this it was the only way i could post the pic,
if mods can please fill free to to move pics to one post to make it easyer to look at thanks


rshermanking

[forgebear]

wow looking good mate would like to see it when painted dave

[BigPanzer]

Hi,

I concur. Very nicely put together. I like the fuel and vent pipes and the extra detail on the mudguards. I see also that they only sent you 19 tyres! There is definately somebody at the factory who can't count - I was a couple of track links and 3 pins short

Peter