Cooling diffs

[Fast Westie]

My race Westfie1d is running an Escort MK2 diff with Quaiffe LSD in an alloy housing (similar to the Elan housing). During my last race meeting I measured the temperature of the diff and it was 125C after 12 mins of racing which seems too high.

 

Since I will be doing some longer races next year does anyone have some ideas for cooling the diff? (looked at oil pumps from Think, but they are expensive and heavy)

 

Thanks

 

The car in front is a Westfie1d wink.gif

[EFA]

Wrong House.......

 

Fat Arn

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[Fast Westie]

Maybe Arnie, butyou lot 'over here' are so friendly to Westfie1d owners that I thought someone may be able to help smile.gif

 

 

The car in front is a Westfie1d wink.gif

[AMMO]

FW

 

If you can't stretch to the pump and rad maybe you could try welding some finning to the casing. I've seen a tuned air-cooled race bike at Daytona with extra fins welded to the barrels and heads to take away the heat. In addition to this you could duct some air to the diff.

 

Might make a bit of difference. Pump and rad must be the best option.

 

Before you do this, is 125 degrees too hot? I don't know, maybe someone else out there does.

 

AMMO

[Fast Westie]

Thanks Ammo

 

The car in front is a Westfie1d wink.gif

[R2D2]

I would imagine that synthetic oil would be ok at this temperature but it is worth checking the viscosity at 125degC and the oxidation resistance.

 

There are a few issues that need considering.

 

The oil film capability to stop tooth wear.

The oxidation characteristics of the oil.

Providing the oil will bear up it should be OK but you also need to sure that the Oil viscosity when cold isn't too high to prevent it flowing properly otherwise some tooth scuffing could occur until it warms up.

 

The other consideration is the bearing temperature. Rolling element bearings may not like running at 125degC depending on the cage material.

 

A bearing with a polyamide cage would have a limited life at these sort of temperatures as the cages would degrade and the bearing clearance would be affected. I realise it is difficult to measure the bearing temperatures but it is an important thing to know. If the bearing clearances go to pot the mesh of the gears may change and this wouldn't be fun.

 

Most bearing manufacturers tend to be a little optimistic in their catalogue claims but normally would rate max. temp as 100degC with EP oils, 120degC with polyglycol based synthetics and 110degC with silicone based synthetics.

 

Standard steel caged bearings tend to have a max. temperature rating of 125degC,

(You can buy special bearings that can work up to 300degC but they require speciased heat treatments to avoid dimensional changes and are very expensive and have long lead times).

 

I generally don't like to run standard bearings at much over 80degC for long duration applications and 12 to 15 minutes is a long time. The temp. rise in a dodgy bearing can easily cause seizure in a few seconds if it is highly loaded.

 

When you next strip the diff I would check that the correct claerance bearing has been fitted. If a tight clearance bearing has been fitted it would heat up quite significantly and heat the oil. It may also be worth checking that the backlash has not been set too tight.

 

 

 

[R2D2]

Just checked the bearing type and I think the standard bearings are FAG 6206-2RS.

 

This bearing has a pressed steel cage and a catalogue max. temperature of 120degC.

 

I believe the modern SKF equivalent may be glass reinforced polyamide but I am not 100% sure.

 

The question really is what is the bearing temperature compared to the diff temperature and how the hell to measure it because it might just be very borderline.

 

Sorry not to be more positive but I have no idea how to correlate diff temp. to bearing temp.

[Morls]

How about forced cool air directed to the diff housing?

 

 

 

Mark