Here's the thing. I've been on this forum for a short while now, reading mostly about getting the highest amount of speed out of the engine. Even a thread about setting a speed record. When I look at the pictures however, all the aircooled motors still use the forced air cooling. Why I wonder? For I think that the reason for this forced air system is because the motors are intended to be used as stationairy engines. When used as a motorcycle engine the drivewind should be more than sufficient to cool the engine. Apart from that a diesel performs best at high engine temperatures (large delta T as opposed to the intake air). Main reason however to get rid of the forced cooling is that at max rpm it uses about 20% of the engine's produced horsepower to pump the air over the cilinder. Horsepower wasted because the forward motion of the bike produces more than enough airflow. So I wonder if there's another reason for keeping the forced cooling as it is?
Furthermore I was wondering if anyone ever tried to convert the forced cooling into a kind of mecanical turbo by blowing the air into the airfilter (seems quite an easy adjustment)?
Maybe these questions have been dicussed a thousand times allready, but again I'm new here so please forgive me if so.
wasted horsepower
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wasted horsepower
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sbrumby
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Re: wasted horsepower
Where do you get your 20% power loss fact from ? My Ruggerini with cowling is rated at 23hp I can`t believe if decowled it could turn out 27.6hp. I have left mine cowled for a couple of reasons. Ease of cleaning the engine, not haveing to defan the flywheel,and not haveing to create a cover for the flywheel. Generally fan cooled engines have much smaller fins but remain cool under all rev conditions.
Sam
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pietenpol2002
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Re: wasted horsepower
That 20% figure does seem rather extreme. It could well apply if one were driving a supercharger. And yet, whatever the losses, when you're dealing with 10 hp (and that's typically an optimistic figure), ever bit counts. Regarding your question, the flywheel fins are quite incapable of generating any effective boost. You'd need something able to produce a few pounds of boost such as an appropriately sized turbocharger or supercharger.
Since my flywheel shroud and fins interfered with both the frame and the planned supercharger drive, I buzzed off the fins on the flywheel grinder. As you noted, the little Yanmars/clones were designed to operate in severe conditions where little fresh air was available, and then run for hours on end without overheating. They are in fact oil-cooled engines that utilize the heat transfer qualities of the aluminum block and head to dissipate the heat via air supplied by he flywheel.
I'm counting on 3 factors to make this work.
1. The fact that I have little to no stop-and-go riding in traffic.
2. With the addition of a strategically placed air scoop for the head, the air passing over the engine at speed will be sufficient.
3. The addition of an oil cooler.
We'll see.
Sorry to dampen your enthusiasm for harnessing the air from the flywheel, but what you really need is something on the order of the little Aisin AMR300 supercharger such as I have mocked up here. You'll note the flywheel cover's not yet built.
Since my flywheel shroud and fins interfered with both the frame and the planned supercharger drive, I buzzed off the fins on the flywheel grinder. As you noted, the little Yanmars/clones were designed to operate in severe conditions where little fresh air was available, and then run for hours on end without overheating. They are in fact oil-cooled engines that utilize the heat transfer qualities of the aluminum block and head to dissipate the heat via air supplied by he flywheel.
I'm counting on 3 factors to make this work.
1. The fact that I have little to no stop-and-go riding in traffic.
2. With the addition of a strategically placed air scoop for the head, the air passing over the engine at speed will be sufficient.
3. The addition of an oil cooler.
We'll see.
Sorry to dampen your enthusiasm for harnessing the air from the flywheel, but what you really need is something on the order of the little Aisin AMR300 supercharger such as I have mocked up here. You'll note the flywheel cover's not yet built.
Ron
Re: wasted horsepower
Sam, a friend of mine owns a company wich builds fans and pumps. They are normally driven bij electric motors. He entered the data of a 10hp Yanmar clone in a calculation program. Turned out that a fan of simular dimensions would require a 3 hp electric engine at 2800 rpm. This is with a safety margin of 50%. Fact is however that the powerdemand of a fan or propellor quadruples with the rpm factor. So at low speeds it will have a low demand for power. But as the revs go up the power demand grows exponentially.
@ Ron, Your build looks nice! I think your absolutely right about the turbo or compressor thing. But I am just wondering if connecting the forced air to the airintake without using turbo or compressor would stil improve the performance. Reason why is that coming again from the standpoint that these are stationary engines, the sideways mounted airfilter reduces power and performance when used as a bike engine. When your driving say 40 MPH the airflow over the filter will create a vacuum in the filterbox. Much like paper is sucked out of your car when you roll down the window. The cilinder therefore is deprived of air. So the intention isn't to create an extra amount of air, but more to counteract the vacuum at higher speeds. But its just a thought.
@ Ron, Your build looks nice! I think your absolutely right about the turbo or compressor thing. But I am just wondering if connecting the forced air to the airintake without using turbo or compressor would stil improve the performance. Reason why is that coming again from the standpoint that these are stationary engines, the sideways mounted airfilter reduces power and performance when used as a bike engine. When your driving say 40 MPH the airflow over the filter will create a vacuum in the filterbox. Much like paper is sucked out of your car when you roll down the window. The cilinder therefore is deprived of air. So the intention isn't to create an extra amount of air, but more to counteract the vacuum at higher speeds. But its just a thought.
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pietenpol2002
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Re: wasted horsepower
I would quite agree that the original equipment air filters are very restrictive. A number of individuals on the forum have noted marked improvement in performance with removal of the stock filter.
But let me argue a bit further regarding the cooling fan. A portion of the flow from the flywheel would need to be diverted from its task of cooling to assist both vacuum and atmospheric pressure in charging the cylinder. However, that air came from the heated environs of the flywheel which sits in close proximity to the aluminum block that's attempting to dissipate engine heat. Some portion of that heat will be carried to the cylinder thus producing a less dense charge, given that heated air is less dense than cold air.
Would we benefit more from a forward facing air scoop placed upstream of a very efficient filter, thereby supplying the engine with a cooler and more dense air supply?
Perhaps if I stopped littering the webosphere with this unscientific drivel, someone knowledgeable could address the matter.
But let me argue a bit further regarding the cooling fan. A portion of the flow from the flywheel would need to be diverted from its task of cooling to assist both vacuum and atmospheric pressure in charging the cylinder. However, that air came from the heated environs of the flywheel which sits in close proximity to the aluminum block that's attempting to dissipate engine heat. Some portion of that heat will be carried to the cylinder thus producing a less dense charge, given that heated air is less dense than cold air.
Would we benefit more from a forward facing air scoop placed upstream of a very efficient filter, thereby supplying the engine with a cooler and more dense air supply?
Perhaps if I stopped littering the webosphere with this unscientific drivel, someone knowledgeable could address the matter.
Ron
Re: wasted horsepower
Ron, I think your knowledge is quite on level to be honest. And most new and refreshing ideas come from people with the abillity to think outside the box, not being hindered bij rules, regulations and imprinted thinking patterns.
You might be right that a scoop is the way to go if no turbo or compressor is used. But then it has to be a kind of ram-air system. But, as you stated, maybe there are other people who can comment on this subject.
Im quite curious though about how your mechanical compressor will perform. This kind of equipment is hard to come by here in Holland. Maybe a G-loader from an old volkwagen golf or polo at the wreckyard. But these are normally completely ruined.
You might be right that a scoop is the way to go if no turbo or compressor is used. But then it has to be a kind of ram-air system. But, as you stated, maybe there are other people who can comment on this subject.
Im quite curious though about how your mechanical compressor will perform. This kind of equipment is hard to come by here in Holland. Maybe a G-loader from an old volkwagen golf or polo at the wreckyard. But these are normally completely ruined.
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sbrumby
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Re: wasted horsepower
Espe I still think your friends calculations are way offline. But if it was correct i have made a big mistake in makeing my bike, because if the fan is pushing 4.6hp then it is also sucking 4.6hp and so i have mounted my engine 90deg out. so if it it was mounted fan faceing forwards it could suck me along.
Sam
Re: wasted horsepower
This would be true if your fan was 100% efficient. It is worth noting that most of the sites for our engines have a Gross HP and then oftentimes a net, mean, or bhp figure as well. It's intersting to note that those values are frequently 10-15% lower than the gross, so you have losses somewhere. I could see the fan being a contributory factor.
Re: wasted horsepower
sbrumby wrote:Espe I still think your friends calculations are way offline. But if it was correct i have made a big mistake in makeing my bike, because if the fan is pushing 4.6hp then it is also sucking 4.6hp and so i have mounted my engine 90deg out. so if it it was mounted fan faceing forwards it could suck me along.
Who knows Sam?But let me just give you this to chew on:
Maybe you have seen a hayblower, sawdustblower, cornblower or even a vacuumcleaner for that matter on the inside. The geometry is the same as the forced cooling on your diesel. So if such a construction wouldn't have any kind of power demand, then why do they need those big motors
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Sphere
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Re: wasted horsepower
Have you actually measured the flow to arrive at this 20%?
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Re: wasted horsepower
No, the program calculated that a fan with the same dimensions rotating at 3000rpm needs a 2,2 kW electric motor .
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Sphere
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Re: wasted horsepower
I understand, but you can imagine this 2.2kW won't hold for a freely rotating fan without a surrounding case. If the fan is built to pump gas in or out, it is a different ballgame, because it is actually performing work.
Now, for my Hatz, the case leaks. I would be surprised if the pressure downstream would be anything other than atmospheric. And indeed, the fan is not designed to perform work, but to provide sufficient cooling. Maybe I can find some data on this subject with our CFD department.
Now, for my Hatz, the case leaks. I would be surprised if the pressure downstream would be anything other than atmospheric. And indeed, the fan is not designed to perform work, but to provide sufficient cooling. Maybe I can find some data on this subject with our CFD department.
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BertTrack
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Re: wasted horsepower
On the note of a cooling fan doing actual work. If the engine blows air past the fins.. it's doing work.
A fan will become more efficient when you streamline the airflow. But even a naked fan will work. Just not the direction you'd like it in.
Having a closed fan housing without an air exit will use less power than a naked fan.
A fan will become more efficient when you streamline the airflow. But even a naked fan will work. Just not the direction you'd like it in.
Having a closed fan housing without an air exit will use less power than a naked fan.
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tappy
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Re: wasted horsepower
The data sheets availabe for Hatz, Lombardini, Ruggerini engines etc typically list an air volume flow required for complete combustion, and an air volume flow required for cooling.
For example, the hatz 2G40 requires 10.5m^3 per minute when running at 3000rpm.
At 30mph the forward speed is around 13.25m/s, so the cross-section of the flow needed to provide sufficient cooling at high power is then 200mm x 66mm - really not very much. Especially when you consider that you're not going to spend long at 30mph and full power unless you're riding up a 1 in 2 gradient (which the oil system can't cope with anyway)
Yes, there might be an issue if you're running any power and stationary, but how often are you stationary on a bike? Only those that don't filter in traffic...
It's worth noting here that a diesel - unlike a petrol engine - controls its power development by fuel ratio alone, rather than throttling, so low power running is also lower temperature running, requiring less cooling.
If a fan is being used to push air through the ducting and over the cooling fins etc then the air will exit the cooling ducts with a static pressure equal to ambient pressure. The airflow is moving however so its total pressure will be slightly higher. Additionally, there will be numerous pressure losses caused by the air passing over the fins, changing direction etc - indeed a reasonable degree of turbulence is useful to give good heat exchange. So even though the air is exiting to atmospheric pressure, the fan will still be doing work to maintain the airflow.
Using that same value of 10.5m^3/min at 3000 rpm, and a notional driving pressure of 1psi, (1 atmosphere is 101325Pa or 14.696 psi, so not a great deal) we have:
0.175m^3 /s x (101325/14.696) = 1200W. So, at 1psi the air flow is using 1200W - or about 1.6hp.
The fan isn't terribly accurately made, as is designed to work over a large speed range, so a generous efficiency would be 75%, in which case the fan is absorbing about 2hp from the crank.
I haven't done any calculations to back up that 1psi pressure drop but it feels about right. I'm happy to discuss further, but perhaps Espe's friend's calculations aren't so wide of the mark after all? As he says, such a fan's power increases with sqaure of it's speed, so if it was using 2hp at 3000rpm, then at 3600 it would be using 3.1hp.
As others have noted - a naked fan will use rather less power by virtue of the fact that it will be generating very little pressure rise. It will still be stirring quite a lot of air but it's probably barely a 10% of that power.
Regarding the different power figures quoted I'll see if I can access the ISO standards, but I always assumed the different values accounted for flywheel inertia. i.e. if you're running at a steady speed then most of the power developed by the engine is driving the load, whereas if you're accelerating then a good deal of the power developed by the engine is being used to accelerate the flywheel rather than drive the load. Subject to maintaining a decent idle speed, this alone is a good reason to reduce the flywheel inertia on these engines. My suspicion is that they are given very heavy flywheels such that in a sudden "no load" event (generator failure) the engine doesn't accelerate so fast that it overspeeds before the control governer has time to react.
For example, the hatz 2G40 requires 10.5m^3 per minute when running at 3000rpm.
At 30mph the forward speed is around 13.25m/s, so the cross-section of the flow needed to provide sufficient cooling at high power is then 200mm x 66mm - really not very much. Especially when you consider that you're not going to spend long at 30mph and full power unless you're riding up a 1 in 2 gradient (which the oil system can't cope with anyway)
Yes, there might be an issue if you're running any power and stationary, but how often are you stationary on a bike? Only those that don't filter in traffic...
It's worth noting here that a diesel - unlike a petrol engine - controls its power development by fuel ratio alone, rather than throttling, so low power running is also lower temperature running, requiring less cooling.
If a fan is being used to push air through the ducting and over the cooling fins etc then the air will exit the cooling ducts with a static pressure equal to ambient pressure. The airflow is moving however so its total pressure will be slightly higher. Additionally, there will be numerous pressure losses caused by the air passing over the fins, changing direction etc - indeed a reasonable degree of turbulence is useful to give good heat exchange. So even though the air is exiting to atmospheric pressure, the fan will still be doing work to maintain the airflow.
Using that same value of 10.5m^3/min at 3000 rpm, and a notional driving pressure of 1psi, (1 atmosphere is 101325Pa or 14.696 psi, so not a great deal) we have:
0.175m^3 /s x (101325/14.696) = 1200W. So, at 1psi the air flow is using 1200W - or about 1.6hp.
The fan isn't terribly accurately made, as is designed to work over a large speed range, so a generous efficiency would be 75%, in which case the fan is absorbing about 2hp from the crank.
I haven't done any calculations to back up that 1psi pressure drop but it feels about right. I'm happy to discuss further, but perhaps Espe's friend's calculations aren't so wide of the mark after all? As he says, such a fan's power increases with sqaure of it's speed, so if it was using 2hp at 3000rpm, then at 3600 it would be using 3.1hp.
As others have noted - a naked fan will use rather less power by virtue of the fact that it will be generating very little pressure rise. It will still be stirring quite a lot of air but it's probably barely a 10% of that power.
Regarding the different power figures quoted I'll see if I can access the ISO standards, but I always assumed the different values accounted for flywheel inertia. i.e. if you're running at a steady speed then most of the power developed by the engine is driving the load, whereas if you're accelerating then a good deal of the power developed by the engine is being used to accelerate the flywheel rather than drive the load. Subject to maintaining a decent idle speed, this alone is a good reason to reduce the flywheel inertia on these engines. My suspicion is that they are given very heavy flywheels such that in a sudden "no load" event (generator failure) the engine doesn't accelerate so fast that it overspeeds before the control governer has time to react.
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Sphere
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Re: wasted horsepower
Interesting writeup. In that case people selling 1B40 generators rated at 6500W continuous must be frauds. Or based on assessment of the empirical data this theoretical model is incomplete. I guess someone with a 1B40 genset needs to pitch in.
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Bugsy_malone 666
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Re: wasted horsepower
Not an expert by anymeans but thought I'd ask a question, with regards to the software generated model, does it take into account purely how much hp the fan alone takes? Obviously flywheels being weighted to help the engine balance and effectively give it a little more umph to start with I would have thought losing 1/5th of your engine power to cooling alone is a fair amount!
However I know from what I have been reading with aircooled vw engines when the cooling system/dynamo is disconnected there is approx 15% power gain.
Maybe ultimately the answer to reducing lost horsepower is to remove the fan/flywheel from the engine if possible and have a smooth flywheel (old villiers used to have a removable fan that was alloy and a cast flywheel) and have an electrically operated small bike fan and thermo switch to keep the engine from getting to hot in high traffic conditions.
However I know from what I have been reading with aircooled vw engines when the cooling system/dynamo is disconnected there is approx 15% power gain.
Maybe ultimately the answer to reducing lost horsepower is to remove the fan/flywheel from the engine if possible and have a smooth flywheel (old villiers used to have a removable fan that was alloy and a cast flywheel) and have an electrically operated small bike fan and thermo switch to keep the engine from getting to hot in high traffic conditions.
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alexanderfoti
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Re: wasted horsepower
When I have a bit of money, i am going to remove the fins and get the flywheel re-balanced, im sure there are gains to be had. I already have a cylinder head temp gauge, so could incorporate a fan quite easily 
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Diesel Dave
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Re: wasted horsepower
Stick one of those square computer cooling fans connected to a temp switch for those heavy traffic moments.
You need air blowing sideways across the head so a little forward pointing duct will do the job when moving.
You need air blowing sideways across the head so a little forward pointing duct will do the job when moving.
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alexanderfoti
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Re: wasted horsepower
My thoughts, an 80mm high flow fan, or a 125cc radiator fan, like the on on my Honda XL125 Varadero.
Will speak with my engineering guy tomorrow to see if he can balance/turn out my flywheel and what the cost would be.
Will speak with my engineering guy tomorrow to see if he can balance/turn out my flywheel and what the cost would be.
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Diesel Dave
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Re: wasted horsepower
Make sure you tell him the original design speed was 3600 rpm, if he spins it up to 6000 thinking it's for a petrol motor it will explode and perhaps kill the operator.
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tappy
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Re: wasted horsepower
Sphere - I'm not saying whether the power used to drive the fan needs to be deducted from the quoted engine power figures, or whether it's already accounted for in them.Sphere wrote:Interesting writeup. In that case people selling 1B40 generators rated at 6500W continuous must be frauds. Or based on assessment of the empirical data this theoretical model is incomplete. I guess someone with a 1B40 genset needs to pitch in.
What I am saying is that removing the fan, or at least preventing it "working" may free up extra power to that already available.
Re: wasted horsepower
Just some info on the computer fans, they are already set up to use 12v power, which is good for us, and they have no problems running as low as 3v if need be, and they generally have very predictable half volt rpms (for example, a fan that runs 2700 rpm should run half that a 6v). You can find fans for about 12$ that move north of 130 cubic feet a minute, which is quite significant airflow, while using about as much power as a dashboard light. You might want to cowl it if you'll be riding wet.
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alexanderfoti
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Re: wasted horsepower
Indeed I will. Im pretty sure cast iron flywheels arent used past 4000rpm anyway?Diesel Dave wrote:Make sure you tell him the original design speed was 3600 rpm, if he spins it up to 6000 thinking it's for a petrol motor it will explode and perhaps kill the operator.
Re: wasted horsepower
Good catch, Diesel Dave!
I had an old 14hp cast iron Kohler, not sure if it broke 3600 though. Flywheel took out a chunk of my shop floor when I was rebuilding it once (thing was massive), then my mother put hydraulic oil instead of engine oil in it (to her credit, the barrels weren't labled, and all looked the same, she meant well) and seized it.
I had an old 14hp cast iron Kohler, not sure if it broke 3600 though. Flywheel took out a chunk of my shop floor when I was rebuilding it once (thing was massive), then my mother put hydraulic oil instead of engine oil in it (to her credit, the barrels weren't labled, and all looked the same, she meant well) and seized it.
Re: wasted horsepower
Thanks Tappy, for the backup. I've ran some tests at my workshop. I took a flywheel and cover from a seized yanclone(10hp) and connected them to a testbench used for testing electrical pumps. The bench showed that running at 3600 rpm the fins use 1.87 kW electrical power. So this is on top of what the electric motor uses when it is not connected to anything. My mind is made up. For my build i'm gonna get rid of the fins. Its the easiest way of gaining extra power.
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Re: wasted horsepower
Don't know quite what your setup is, espe, but google tell me 1.87kw is around 2.5hp, which is quite a bit.
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Nanko
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Re: wasted horsepower
Performing such test without a load is not accurate.
Blocking the outlet or inlet stops the airflow through the fins and the amount of power taken will be much lower , if not zero.
Blocking the outlet or inlet stops the airflow through the fins and the amount of power taken will be much lower , if not zero.
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BertTrack
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Re: wasted horsepower
The "load" would be the air being moved around. And even blocking the inlet/outlet doesn't stop a fan from moving air. It may circulate (bleed) past it's blades but moving air it will. Unless you create a vacuum in there.
Those blades are hitting molecules and they demand to be paid in the form of energy.
Those blades are hitting molecules and they demand to be paid in the form of energy.
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Nanko
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Re: wasted horsepower
OK I should have written "almost stops the flow", but a fact is: (edit)fan power consumption depends a lot on the load.
There is a nice write-up from albertaphil in de "doing things with air section"
He states:
The cooling system is not capable of producing any pressure at all. Nor are air scoops. An aviation magazine I used to read had an article on such things, and the resident expert (Peter Garrison in Flying magazine) stated that an air scoop on the cowling of an aircraft will produce 1psi at about 300mph.
If the fan indeed produces 1 psi I doubt the airflow at 60 mph will be enough to keep the engine cool enough
There is a nice write-up from albertaphil in de "doing things with air section"
He states:
The cooling system is not capable of producing any pressure at all. Nor are air scoops. An aviation magazine I used to read had an article on such things, and the resident expert (Peter Garrison in Flying magazine) stated that an air scoop on the cowling of an aircraft will produce 1psi at about 300mph.
If the fan indeed produces 1 psi I doubt the airflow at 60 mph will be enough to keep the engine cool enough
Last edited by Nanko on Mon Sep 10, 2012 8:02 pm, edited 2 times in total.
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BertTrack
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Re: wasted horsepower
Power/fuel consumption is completely based on the load. The fan load will be a significant factor if you don't add an additional load. But running it with an additional load doesn't make the fan-load insignificant. 