Oil Temps Again

[GregT]

Those temps look pretty safe for a good quality race oil. The installation looks very similar to several rigs i see local to me but the late stuff - LCR's etc which are appearing here - have a better integrated air intake and duct sealing setup.
All you can do at this point is tracktest and see how the temps go.

 

[Kyler]

Those temps look pretty safe for a good quality race oil. The installation looks very similar to several rigs i see local to me but the late stuff - LCR's etc which are appearing here - have a better integrated air intake and duct sealing setup.
All you can do at this point is tracktest and see how the temps go.

Thanks! we'll know in two weeks. I'll post results here.

 

[Grimly]

I'm just wondering how much cooling burden is being shifted to the oil if the direct engine cooling is compromised. Drag is always a consideration, but as has been mentioned, low drag cooling can be attained.

 

[posplayr]

I'm just wondering how much cooling burden is being shifted to the oil if the direct engine cooling is compromised. Drag is always a consideration, but as has been mentioned, low drag cooling can be attained.

Obviously a lot; why else would a 750 run even full out overheat in 15 min.

And I would think you are quite right in bringing up cooling burden. This is an air cooled engine and there is going to be a limit to how much heat you can disapates through the oil no matter how much air you run brought the cooler. Carried to excess he might even see very cool oil temps but run high head temps.

 

[Grimly]

Yep, I would guess it needs more airflow to barrel and head, even if the rider is a bit toasted. Even at that, a solution can be reached - perhaps the Manx TT sidecar outfits of the 70s and 80s could be robbed for design pointers - they did more than 15 minute stints and (usually) didn't expire too much.

 

[GregT]

Aerodynamically, a classic or post classic sidecar outfit is roughly equivalent to doing a top speed run in your van with all the doors and windows open - and a passenger hanging out the side door...

Historically, the solution to engine cooling problems was to use Methanol fuel which sidestepped most of the cooling issues. Unfortunately, a lot (not all ) of the sanctioning bodies will not allow it's use now which can lead to the problems seen here.

Compounding the problem is the overriding requirement that the outfit appear correct for the period. This limits aerodynamics to subtle improvements at best.

I'd hope that the oil cooler installation will mitigate the overheating problems enough to get a decent season out of the rig.

 

[Kyler]

the good news so far is the oil analysis reports haven't shown any signs of oil degradation due to heat. At worst I'll have to change oil after every race weekend. That is a small price to pay.

 

[Kyler]

I'm just wondering how much cooling burden is being shifted to the oil if the direct engine cooling is compromised. Drag is always a consideration, but as has been mentioned, low drag cooling can be attained.

The NACA ducts (although not period but tolerated) point at the jugs. That is the best I can do on that right now. I'll puzzle through cooling more after the next race and have more data. More to come!

 

[Kyler]

I'd hope that the oil cooler installation will mitigate the overheating problems enough to get a decent season out of the rig.

Same here; one race down and 6 to go. My plan is to drop a GS1100 motor in it over the winter. I've saw a lot of GS1168 motors on the Phillips Island entry sheet. What is the URL of the NZ sidecar club? I might be able to get more ideas from them.

 

[posplayr]

Aerodynamically, a classic or post classic sidecar outfit is roughly equivalent to doing a top speed run in your van with all the doors and windows open - and a passenger hanging out the side door...

Uhhhhhh not sure that I can accept that even on face value.

At a given speed and altitude, aerodynamic drag is principally a function of shape factor. A flat plate Cd is approx 1.2. A square van with doors open might have a Cd somewhat above 1, I suspect the Cd of that faired trike is quite a bit lower than 1.0. A reasonably aerodynamic car these days is like .35, so I would guess that bike is probably no worse than 0.75.

Horsepower required to achieve a specific velocity is proportional to the Cd times the cube of velocity. So by a natural process the design probably evolved to one of much higher efficiency that the van, part of the reason for the closed off engine venting.

Frontal inlet drag is going to be largely a function of area alone (ignoring flow out of the cooler.) , but I suspect overall engine cooling efficiency is very much dependent of whether that are is allocated to engine air flow v.s. cooler air flow. That optimization is something that I doubt has been fully explored.

In fact if it was that bad, you couldn't make it any worse by letting some of the frontal area catch some wind to cool the engine instead of the oil cooler.

 

[GregT]

Same here; one race down and 6 to go. My plan is to drop a GS1100 motor in it over the winter. I've saw a lot of GS1168 motors on the Phillips Island entry sheet. What is the URL of the NZ sidecar club? I might be able to get more ideas from them.

Go onto Kiwibiker forum - racing section, look for the sidecar racing thread.
Jellywrestler who is a member on here is one of the four or so guys who certify sidecars for racing in NZ and would be worth contacting too.
There is a quite a lot of trans tasman racing done so the guys on the sidecar thread will tell you what they know.

 

[GregT]

Uhhhhhh not sure that I can accept that even on face value.

At a given speed and altitude, aerodynamic drag is principally a function of shape factor. A flat plate Cd is approx 1.2. A square van with doors open might have a Cd somewhat above 1, I suspect the Cd of that faired trike is quite a bit lower than 1.0. A reasonably aerodynamic car these days is like .35, so I would guess that bike is probably no worse than 0.75.

Horsepower required to achieve a specific velocity is proportional to the Cd times the cube of velocity. So by a natural process the design probably evolved to one of much higher efficiency that the van, part of the reason for the closed off engine venting.

Frontal inlet drag is going to be largely a function of area alone (ignoring flow out of the cooler.) , but I suspect overall engine cooling efficiency is very much dependent of whether that are is allocated to engine air flow v.s. cooler air flow. That optimization is something that I doubt has been fully explored.

In fact if it was that bad, you couldn't make it any worse by letting some of the frontal area catch some wind to cool the engine instead of the oil cooler.

We're talking specifically classic and post classic chairs - which are a quite different case to modern LCR's for instance. The long bikes are effectively half a formula car aerodynamically.
If you want to see how literally everything can be optimised, have a look at a modern rear engined LCR.
A lot of the classic and post classics don't actually bother with a fairing or trying to streamline anything....why bother on short circuits where you can barely top 100mph ? Better to be able to climb all over the outfit...

 

[posplayr]

We're talking specifically classic and post classic chairs - which are a quite different case to modern LCR's for instance. The long bikes are effectively half a formula car aerodynamically.
If you want to see how literally everything can be optimised, have a look at a modern rear engined LCR.
A lot of the classic and post classics don't actually bother with a fairing or trying to streamline anything....why bother on short circuits where you can barely top 100mph ? Better to be able to climb all over the outfit...

OK, with this in mind, you are making a strong argument that better ducting for engine cooling, should have little effect on a poor aerodynamics shape. My point being that no matter where the ducting is, it's effect on drag is similar, in an aerodynamically inefficient design it is probably of minimal overall effect anyway. So perhaps the design is better served by more engine ducting or at least not oil cooler ducting to the exclusion of the engine cooling.

The whole bottom of the failing is wide open, I suspect an opening in the cone of the nose would do wonders for engine airflow and probably reduce the head temperature even if the oil temp is already low from forced air flow though the cooler.

 

[Kyler]

once I have the oil at a temperature I like, then I'll look at the cooling of the motor. The pic below is pre-paint job but there is a NACA duct on either side that dumps on the cylinders.

 

[posplayr]

once I have the oil at a temperature I like, then I'll look at the cooling of the motor. The pic below is pre-paint job but there is a NACA duct on either side that dumps on the cylinders.

Compare those two side ducts in terms of projected opening area that of the cooler's projected area. Also consider what Mmattockx described before, about an expanding duct.

Air entering a duct with increase cross sectional area will slow the velocity, presumably increasing cooling efficiency through the cooler.

Those side ducts are doing the opposite compressing the flow and increasing the velocity probably running right past the air around the engine.

Following Mmattoxks suggestion if you glassed in a cone shape into an opening in the nose you would get exactly what the doctor ordered. Small inlet, with expanding cross sectional area.

The more I look at that nose it is really just like a big expanding duit. Just cut the nose straight off. Of roll the corners a little so it is not such a knife edge.

Originally Posted by mmattockx View Post

Ideally the inlet hole area is quite a bit smaller than the cooler area and the ducting smoothly expands from the inlet out to the cooler. This slows the air down and lets it recover pressure before passing through the cooler fins, then the exhaust air should be ducted smoothly out into a low pressure zone. .

 

[GregT]

OK, with this in mind, you are making a strong argument that better ducting for engine cooling, should have little effect on a poor aerodynamics shape. My point being that no matter where the ducting is, it's effect on drag is similar, in an aerodynamically inefficient design it is probably of minimal overall effect anyway. So perhaps the design is better served by more engine ducting or at least not oil cooler ducting to the exclusion of the engine cooling.

The whole bottom of the failing is wide open, I suspect an opening in the cone of the nose would do wonders for engine airflow and probably reduce the head temperature even if the oil temp is already low from forced air flow though the cooler.

i'm not making a statement about how the ducting affects aerodynamic shape at all - i'm pointedly avoiding the argument...

What you've got to realise is that the argument is academic as THE OUTFIT MUST MATCH CORRECT PERIOD APPEARANCE. Sorry to shout but i'm a long way away...He can't do very much at all to improve it - either areodynamically or in cooling efficiency - without incurring the wrath of the dreaded eligibility committee. He's stuck with what has provably been used in the relevant period.

 

[Grimly]

Ok, what about retaining the nose shape but making the necessary pointy bit out of mesh/expamet?

 

[posplayr]

i'm not making a statement about how the ducting affects aerodynamic shape at all - i'm pointedly avoiding the argument...

What you've got to realise is that the argument is academic as THE OUTFIT MUST MATCH CORRECT PERIOD APPEARANCE. Sorry to shout but i'm a long way away...He can't do very much at all to improve it - either areodynamically or in cooling efficiency - without incurring the wrath of the dreaded eligibility committee. He's stuck with what has provably been used in the relevant period.

We OK I admit, I have no idea of what the issue is but it certainly does not seem to technical. That is coming out load and clear.

For example, If OP were to put scoops up under the fairing to pull the air that is traveling below the fairing up on the engine area, I would imagine cooling would be greatly enhanced. Buts, I would also appear that that would have so much visual impact so as to not have a "CORRECT PERIOD APPEARANCE".

Of course aluminum foiled oil cooler ducting in period correct political signage is perfectly legal Maybe OP can put a peltier, on the oil cooler, so the electrical load is increased lowering the cooling problem from the shunt R/R. Now that is starting to make a lot more sense.

 

[Kyler]

I'm not touching any ducting other than the oil cooler for now. One change at a time.

But I did order a TT Tech cylinder head temperature gauge. Knowing what is going on right now is job #1.

 

[Grimly]

I'm not touching any ducting other than the oil cooler for now. One change at a time.

But I did order a TT Tech cylinder head temperature gauge. Knowing what is going on right now is job #1.

Well, you might find your head temps are ok, but if your oil's hitting over 302 and off the gauge, I kind of doubt it.
There's a lot to be said for synthetic oils and this rig is proof of every one of them - I take it you're using synth? I just assumed that.