Classic UK Minitrix Models  -  Ivatt 262
Valve Gear

I thought that this would be easy after doing the same job on the Mallard and on the 2-10-0 9F. How wrong I was. It was a pain in the proverbial ........ The following sequence comes about from having tried all sorts of other ways, and it involves something that I don't like to do - bending. But unless you have another suggestion - here goes....

First prepare the chassis. All of the wheels should be in place, they should be aligned, and you may have the coupling rod in place. I didn't. Take out the motor, and turn the chassis upside down. Remove the front screw of the base plat, slacken the rear, and slip out the front bogie. Don't disturb the wheels. Screw the baseplate back up again.

Remove the cylinders. They slide off individually from their respective side of the engine. You need to gently prise the plastic tab over the raised metal 'lock'. Once clear, it just pulls off.

Now - check if the rear of the gearbox will lift up without having to pop out the gearbox axle. I didn't think it would, so I pushed it out anyway. I've done it so many times now, that it comes out quite easily.

 

Remove the con rod and the piston rod from the valve gear assembly on each side. Rest the mechanism in place behind the gearbox. Gently prise open a gap, and slide the valve assembly underneath it into its locating slot. It should move freely left to right for a few mm. Move it to the right as far as it will go.

 

I really hate doing this next bit, but I could find no other option. I couldn't find any way that I could get all of the valve gear into the respective locations at the same time, without damaging something. I tried many times, without success. I resorted to this method after a lot of swearing and cursing as the valve gear repeatedly fell out of their locations. Maybe if you have better eyesight, smaller fingers and 6 hands, you will succeed where I failed. But this method works nicely, and you can focus on one side at a time.

 

Gently. Very gently. Spring the right and left hand side slider mechanisms outwards. This needs to be just enough to clear one cylinder block when it is at the end of the metal beam. The plan is to put the cylinder block onto the ends of the slider rods, and then push the cylinders back onto the loco frame. For this side, you can slide the valve gear over slightly to the right. But don't do that yet !

First, lay the loco on its left side. Slide the piston forward so that it sticks out further than the slide bars, and insert the piston rod into the hole in the cylinder. Keeping the piston in its hole, slide the plastic cylinder block onto the ends of the slide bars. I needed a magnifying glass to see the tiny slots for this. Be careful not to put any strain on the plastic slider as you do this - you may need to let the slider and the piston move back as you push the cylinder block onto the end of the slide bars.

Push the cylinder onto the beam. Before it clicks, make sure that the conrod is still in the right position. If not, manoevre it back into position before clicking the cylinder block onto the frame.
Don't try to bend the valve gear back into shape - once clicked, the cylinders will hold the gear against the springiness. This is important. It would only take a few bends to work harden the valve gear enough for it to snap off.

Fit the coupling rods, the push fit bolts on the front and rear wheels.

Sorry about the out of sequence photo. I forgot to take one at the time !

Put the eccentric crank into the hole of the con rod, and manoevre the assembly into position so that the crank pin is over the hole, and the eccentric rod coupling is almost over the axle of the wheel. Push gently into place. Dont push it home yet though.

Now do the same with the other side. The valve mechanism will not move across as far this time, so the slider rods need to be bent a bit further. This could strain the plastic slider, so keep an eye on it as you focus on getting the piston rod and the slider rods into the holes in the plastic cylinder block.

 

 

The only time that there is risk of any strain, is when you need to get the cylinder block over the end of the bar of the frame. Move the slider and piston backwards as soon as possible to reduce the risk of putting any strain on this. Push the cylinder block down, but don't let it click home until you have checked that the eccentric rod and con rod are in roughly the right position.

 

Locate the pins in the coupling rod and push them loosely into place in the wheels. Pin slightly out of focus here, sorry.

Insert the eccentric coupling and con rod onto the crankpin, locate the joint over the wheel axle, and press home loosely.

 

The engine is not in place, so give the chassis a push around and watch the gear operating to check for any issues. (If you removed the gearbox axle, make sure the gear is not in place before you do this). If it is ok, push all of the pins home, and check again.

 

Replace the bogie wheels, making sure that the contact strip is correctly located. Keep your fingers firmly on the wheels. If they pop out now, you may have to go back to the beginning!

Oh, and if you removed the gearbox axle, don't forget to put it back !

Maintaining Classic UK Minitrix Locos
The Minitrix trademark is currently owned by Märklin Inc.  Gebr. Märklin & Cie. GmbH, Stuttgarter Straβe 55-57, D-73033 Göppingen, Baden-Württemberg

Website ©2002-2018
JFHeath