T90 Surging and Potential Cure

RAK402 · T90 Surging and Potential Cure

I had noted comments from the forums regarding the T-90 surging (someone actually had it on video, I think). Mine did this too, so I thought it was just the way it was. I thought perhaps it was just choking on a buildup of condensation in the plastic turbine housing.

The other day, I ran mine three or four time-part of the time driving the Wilesco Modelplate Workshop (three tools). It struggled to do this and exhibited the same surging (speeding up then slowing down) as it had in the past (I had only run it about a half dozen times before).

It slowed down toward the end of the run, and exhibited binding (you could hear it squeak when you turned it over) so I took the turbine itself apart this morning.

There are four bearings (two on the idler, two on the main turbine shaft). These bearings are neither shielded nor sealed and appeared never to have been lubed-this is hard to discern, as the bearing facing the turbine wheel is in a perpetual state of being steam-cleaned.

The bearings were bone dry and binding. I soaked them in Triflow and freed them up (they will still need to be replaced, at some point).

There is no way to lubricate the tubine shaft bearing without taking the turbine apart (the idler can be removed easily by removing a nut). Taking the turbine wheel out is something to avoid doing very often, as it is entirely plastic and pressed together.

There is a space between the two bearings with an are gap between. Using a small drill, I made a hole through which the bearings can be lubricated with a needle oiler, while the turbine is still mounted to the base plate.

I did fill the gap with steam oil prior to re-assembling the turbine. I also installed a thin washer between the bearing and the turbine wheel to slightly increase the clearance between the turbine housing and the turbine, and to provide a small barrier between the bearing and the steam.

I have run it several times since the surgery was performed. For the first time since I have had it, the turbine runs at a steady speed until the fire drops. After re-stoking the fire, it will build up pressure again (even while running) and run steadily until the water level causes me to remove the burner.

I have been using TriFlow as oil in the bearings recently (a knowledgeable person recommended a lighter oil). The turbine is still running fine.

Spokesmann

Look forward to seeing these unusual engines in action!

avenger

Intereting post !

silverfoxsteam

Good account of your solution to what is clearly a shared problem.

I've not heard of Triflow, what's the viscosity and is it available in the UK?

RAK402

Stephan,

I apologize. I do not know the viscosity or whether it is available in the U.K.

I use it on my model helicopters in critical areas. It is Teflon particles in suspension.

It works very well for a number of applications.

silverfoxsteam