Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Three wheeler polished engine

Ok the temperature is a new aspect. Did anybody hear that there are in reality more temperature problems with polished engine compared to a black engine on a TW. Particularly after a blower is installed.

Once knew a harley mechanic who was making his own custom bikes way back in the day. He'd had to fix or trash too many chromed motors due to heat problems. Most of the bikes with chromed blocks were strictly for show and were never meant to be run but the idea, and the bling, picked up and ran away.

They look great but all the heat energy is reflected back into the block instead of radiating away. This is a classic demo of physics in action. Black is the optimal color. The raw aluminum would be next and chrome would be the worst.

I believe that this could happen with chrome. But if the same happens in reality to the polished aluminum engine from S&S why no one writes about this special heating problems here or in the new Three Wheeler book? Has anyone heard about this problem by Morgan dealers?

Can this be the cause of the breaking down the cam belt behind the chromed cover ?

I believe it's not common knowledge. The three wheeler book is just a collection of knowledge out there. If you wanted to test it properly, you would properly need the exact same setup, first polished chrome, then perhaps even remove the chrome, and then paint it black. But it's a physics question, and black does lose heat faster than chrome or white. It has little to do with reflecting, unless it is on plastics of some kind (i.e. some kind of insulation). If directly on metal, it is more a question of heat emission, than it is about reflecting radiating heat back. However, the end result is the same: Chromed or white anything will retain more heat for longer than the same item in black.

It could be a factor, but I honestly don't know if it's the cause. It sort of depends on how big a margin there is, so to speak. If, say, it needs to drop 1.000 "units"* to stay within the safe temperature zone for the timing belt, and a black cover will only drop 300 "units", then the timing belt would still be toast. However, every little bit would help (including using the spacers), I'd think.



*Energy is measured in kilojoules, but since I have no hard facts about the energy being produced, the energy that needs to dissipated, the exact energy difference between a black and chrome cover, the exact heat energy needed to destroy a belt etc., I figured I would use a non-descript "unit".

New mechanic this time. When I had to replace the cam belt I took it to a custom chopper place and they were very familiar with the S&S. Heat IS the main culprit. Every piston engine usually stops in the same place. Proof of that is when you have to replace the clutch and then you can see that the starter solenoid has worn only one area where it always engages the gear ring first when starting.

This guy noticed that the breaks were always where the cam belt rested on the main pulley, which is the end of the crankshaft. There were scorch marks on the belt where it got cooked while it was stationery after running.

I can only surmise that when the engine is running everything in that cam box is at the same temp and there is also air cooling going on. When it stops and no more air flow all that heat is going to move in to a cooler area from a hotter area.

Just doodling……

Comparing the radiant emissivity of black enamel with polished aluminium or chrome we have a ratio of about 0.8: 0.06 (at room temp) or about 13. i.e. at the same temperature a black enamelled surface will radiate 13 times as much energy as a polished metal surface.

The radiant energy is proportional to the temperature (in degrees K) to the fourth power. Therefore, in order to radiate the same amount of heat energy, the polished surface must be 1.9 times (fourth root of 13) as hot as the black enamelled surface. Relating this back to our more usual degrees C, if the black enamelled surface is at 100 deg. C, then the polished surface has to be at a rather warm 435 deg. C in order to dispose of the same radiant energy.

All of which makes me think that an air-cooled engine (about which I have no real experience) is cooled mainly by convection rather than radiation. Household radiators are normally painted white whereas black ones would dispose of heat at a much lower temperature (and would be easier to keep looking clean). But we don’t do this because, my guess, like the engine, they cool themselves mainly by convection rather than radiation.

While we’re at it, let’s look at that bane of our lives the bevel box. This unit at 70 deg. C (my single measurement after motorway cruise) will radiate:
0.05 (Area m^2) X 5.67 10^-8 (magic constant) X 343^4 (absolute temp ^4) X 0.2 (emissivity for oxidised aluminium) = 7.8 watts

All v. approximate, but indicates that only a tiny proportion of the 2 Kw (5% of maybe 50HP) being generated as losses in the BB is radiated. So painting it black or even pink with blue spots will have negligible effect on heat dissipation. Go for fins.

Data from ‘Engineering ToolBox’ for those interested.

Knickers probably in a tangle (they often are), but just some thoughts.

It makes me think that at 140 degrees celcius, that it may be a good idea to have it black so the convection cooling which is also present can work its best. No doubt that convection is a huge factor, but we are not talking about cooling it to, say, 80 degrees. We are talking a small percentage increase in cooling. From, say, 180 degrees to 160 degrees is a decrease of heat around a mere 11 percent, something I bet will make a difference combined with it being out in front in the wind.

In other words, I think you understate somewhat the importance of radiant heat. If it didn't radiate heat, the heat couldn't be removed by convection. So, an increase in radiation of a mere 10 percent (you're talking a 13-fold increase in radiated heat) could well translate to ten percent more heat being blown away (i.e. convection). If I had a proper set up (and the time) to do so, I would make myself a couple of pieces of alu sheet - one chrome, the other black. Put it atop of some insulation with spacers and heat it up to, say, 150c, then use a fan to blow on both top and bottom, and then compare the two. If the radiant heat doesn't matter much (7.8 watts and so on), then there will be practically no difference in temperature after a set time.

after all the comments I'll put a black pajamas with a black nightcap and wait until tomorrow to call S & S to blame them for having made me a polished engine.
  his last day in France you better have an engine heater because with weather temperature reaching an oil temperature of 90 ° C must circulate continuously over 5000trm because the oil temperature in trouble ateindre 80 ° C normally travels on the road with normal traffic, I prefer to travel with a thick oil to 120 ° C against 80 ° C with a light oil.