Model Engine Maker

Supporting => Engine Ancillaries => Topic started by: Brian Rupnow on July 06, 2014, 12:34:36 PM

Title: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 06, 2014, 12:34:36 PM
As you are probably all aware, I have just finished a two month build of my version of Malcolm Stride's engine, the Jaguar, which is essentially half of a Bobcat. My engine ended up with many changes, and got rechristened the Canadian Cub. It is a sweet little engine, with a totally enclosed crank-case and an oil sump and splash lubrication. The only trouble is, the engine runs terribly hot. Malcolm ran his with a propeller, which no doubt kept it cool thru the air movement the propeller created. I am afraid of propellers, because at hi speed they become somewhat invisible, and have a tendency to cut off fingers from old fools who inadvertently stick their fingers in the invisible propellers at speed!!! THUS--I have determined to create a small. belt driven cooling fan to keep the temperature down into a reasonable range on my engine. I haven't seen any posts before on similar subjects, so you may find this of interest.
__________________
Brian Rupnow
www.rupnowdesign.com
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 06, 2014, 12:41:31 PM
As you can see, my engine is not very big, being only about 5 1/2" (140 mm) tall, with a 3" (76 mm) diameter flywheel. This only leaves me 2 1/2" (63 mm) for a fan and fan shroud, as I only want to cool the cylinder and cylinder head. The crank-case is not overheating, and a larger fan would completely overwhelm the engine.
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/CANADIANCUBASSEMBLYWITH2INCHFANMOUNTED_zps93c8cbea.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/CANADIANCUBASSEMBLYWITH2INCHFANMOUNTED_zps93c8cbea.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 06, 2014, 12:46:08 PM
My original thoughts were to use a computer fan, which is close to the right size. Unfortunately, computer fans are all driven by a D.C. motor, and the fan hub is part of the motor housing. This leaves you with an enormous center hub and very little blade. I need airflow in that center area, so decided to search for a small (2") diameter fan with a small hub.
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/computerfan-2001_zps91949ac2.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/computerfan-2001_zps91949ac2.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 06, 2014, 12:53:52 PM
Fortunately for me, I was able to find a 2" diameter 10 blade fan with a small hub and a 3/16" (5 mm) center bore with set screws. The pitch is correct to blow air over the cylinder when driven clockwise, which is the rotation of my engine.
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/2C953_AS01fan_zpsad0899f0.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/2C953_AS01fan_zpsad0899f0.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 06, 2014, 01:02:11 PM
At speed, I am sure that this little aluminum fan would wreak bloody mayhem with unsuspecting fingers as well, so it will have a shroud fitting around it, which I will make from 2 1/16" i.d. steel auto exhaust tubing. The center hub will be a piece of 1/2" (13 mm) o.d. mild steel, with a bronze bushing of 3/16" pressed into it, and the hub will be supported concentric to the outer rim with 3 pieces of 1/16" (1.5 mm) mild steel plate welded or silver soldered into place. The shaft and pulley will be turned from one piece and the groove in the pulley will line up with the groove in the starter hub on the face of the flywheel. I will use a 3/32" diameter rubber o-ring for my drive belt, and the fan will turn at roughly twice the engine speed.
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/2INCHFANASSEMBLY_zpse942efb3.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/2INCHFANASSEMBLY_zpse942efb3.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 06, 2014, 01:09:42 PM
The fan shroud will be supported by a couple of brackets which pick up one of the cylinder head bolts and one of the cylinder to crank-case bolts. These brackets will again be made from 1/16" mild steel and silver soldered or brazed into place. The fan shaft is cantilevered out the side away from the engine cylinder, so the fan should be easy to install in the shroud from the non bearing side. When installed on the engine, the cylinder itself will serve to keep pokey fingers out of the fan. I believe that since the engine itself is all built from brass and aluminum, I may resort to painting the fan and supporting shroud---possibly red for the fan and flat black for the shroud itself.
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/2INCHFANASSEMBLY-FROMREAR_zps5a17dd3a.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/2INCHFANASSEMBLY-FROMREAR_zps5a17dd3a.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Graham Meek on July 06, 2014, 01:16:55 PM
When I decided to build an air cooled version of Edgar T Westbury's Seagull engine, cooling the engine was always going to be a challenge. An engine driven fan was considered, the fan wanted to be efficient and not draw on too much engine power. I thought of using an old power supply cooling fan but driven by a belt drive off the crankshaft. Talking it over with one of the electronics engineers at work he suggested using the 12v DC power supply from the ignition and running it through a bi-metal thermostatic chip so the fan would only cut in as required.

I chose a chip that closed at about 90 degrees C as it is around this temperature that most auto-mobile thermostats open. In use the fan works a treat and the engine will run for hours on end, it is a great source of amusement with my Grandson who regularly reminds me to top the tank up. The chip was sited at the rear of the engine so as not to be in the direct air stream from the cooling fan.

My best regards
Gray,
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 06, 2014, 01:17:00 PM
This is the engine which the fan will be installed on. I am just waiting now for the fan itself, which is supposed to take a week to get here when ordered from Acklands of Canada.
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/JAGUARCARBURETOR001_zps35c9893a.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/JAGUARCARBURETOR001_zps35c9893a.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: philjoe5 on July 06, 2014, 02:00:43 PM
Quote
The only trouble is, the engine runs terribly hot

Brian,
I'm curious, did you take a temperature measurement?

I'm sort of in the same boat.  My recently completed air cooled Bonzer runs a head temperature of about 285 F after a half hour run.  I was wondering whether this was a bit too hot.  Last time I mowed the lawn with my air cooled Briggs/Stratton the head temperature was 440 F at the end.  So I'm thinking the Bonzer is way inside the safe limit.  I do get some pre-detonation near the end running with Coleman fuel but I think I can eliminate that by switching to gasoline.

Not to say a fan wouldn't be a neat addition.  So I'll be following along here.

Cheers,
Phil
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 06, 2014, 02:04:24 PM
Philjoe--I see that Princess Auto has a hand held scanning thermometer for $15 Canadian.  May buy one before I make this change just to try and get comparative figures.---Brian
Title: Re: Cooling Fan for model I.C. Engines
Post by: Ian S C on July 06, 2014, 02:32:59 PM
Here is one of my early hot air motors with the fan from a computer driven from the motors own generator.  The motor is my version of James G. Rizzo's Dyna.     Ian S C
Title: Re: Cooling Fan for model I.C. Engines
Post by: philjoe5 on July 06, 2014, 03:05:30 PM
Brian,
That's what I used to take the temperature measurements.  Works great.

Ian,
I like that setup.  Would you have a video of it in action?

Cheers,
Phil
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 07, 2014, 08:52:42 PM
Well Damn!!!---And I do mean that with all my heart. I got a call today from Acklands that my fan had come in, so I rushed right over. The diameter was right. The hub bore was right.---But the direction of pitch was exactly opposite of the picture showed on their web page!!! I pointed that out to the lady on the counter, who immediately told me that was no problem---just turn the fan around. I think I was able to get it through her head that it wouldn't make any difference. Only changing the direction of rotation would make the fan blow instead of suck!!! She seemed a bit dazed, but said she would return it and there would be no charge. So---I guess I will build my own fan after all. Already ideas are percolating through my head. I would rather use brass than steel, because the hub and blades have to be silver soldered together, and I find the brass a tiny bit easier to silver solder, plus the color of the silver solder matches the blade color.---Brian
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 07, 2014, 09:27:42 PM
Well---That doesn't look so bad!! The hexagon hub measures 0.541" across the flats x 3/8" long, the blades are .430" x 1/16" x 0.729 long. Overall diameter is still 2". I have shown the fabricated fan in a second model beside the overall assembled model to show better what it looks like. Of course, this will require some kind of jig to hold the blades in exact position while I solder them to the hub.
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/2INCHFAN--FABRICATED_zps0b75ebb2.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/2INCHFAN--FABRICATED_zps0b75ebb2.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 07, 2014, 10:07:11 PM
Okay--this will work for a soldering jig. My only concern is that after I get one blade soldered on, will the heat from soldering the next one on make the first blade fall off. I can avoid this to some extent by cooling the assembly off between blades and "skipping around", but as more blades get added, this becomes harder to do.
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/FANJIG_zps9cdc391e.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/FANJIG_zps9cdc391e.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Johnmcc69 on July 07, 2014, 10:39:31 PM
Why not just mill some 1/16" slots to locate the blades?

 John
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 07, 2014, 11:51:34 PM
Johnny--I thought about that, but I like the look better the way I designed it. I have a lot of scrap setting around to make a jig. One way or another, I will show my results.---Brian
Title: Re: Cooling Fan for model I.C. Engines
Post by: Jasonb on July 08, 2014, 07:50:12 AM
I think you will loose a lot of heat into the jig and have to put extra into the work which will melt existing joints and possibly even the brass blades which will heat up before the hub.

Lay it on a flat firebrick with small blocks of metal at the tip of each blade to keep them in place

Dose it really matter if you suck or blow? Seen plenty of electric fans mounted either side of car radiators.
Title: Re: Cooling Fan for model I.C. Engines
Post by: Maryak on July 08, 2014, 08:01:21 AM
Dose it really matter if you suck or blow? Seen plenty of electric fans mounted either side of car radiators.

Yes, I wondered about that too.

Best Regards
Bob
Title: Re: Cooling Fan for model I.C. Engines
Post by: Ian S C on July 08, 2014, 02:27:05 PM
Phil, sorry no video.  That motor, built in 1994 has done over 2000hrs of running,  I tried to run it to death, at 2000 hrs I had to replace the crankshaft, and the con rods.  When I reassembled the motor I had to open out the carbon impregnated bush in the piston that guides the displacer rod, it must have got oil on it, and swelled.  It goes as well, or better today than it did 20 years ago.
Title: Re: Cooling Fan for model I.C. Engines
Post by: Graham Meek on July 08, 2014, 04:40:39 PM
This is just a casual observation and in reality it probably does not matter. The question of whether to blow or suck air over the engine is a vexed one. The Gas laws tell us that if a gas is compressed it heats up, therefore a fan forcing air over an engine is going to warm that air up initially. Now whether there is a benefit in that as soon as this air expands it cools down and during this cooling down cycle it will absorb more heat from the engine I cannot say. On the other hand air being drawn over the the engine is already at ambient and not subject to any compression, no matter how small.

If there is someone more versed in thermodynamics that can answer this conundrum I for one would appreciate the information.

My best regards
Gray,
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 08, 2014, 07:30:09 PM
The jig worked very well. It looks a bit crude in these shots, but it did keep everything aligned while I silver soldered the blades to the hub. Heat from soldering the blades on did not cause the solder on previously soldered blades to let go and have the other blades fall off. (I have experienced that kind of thing when working with soft solder.)
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/FANJIGAMDFAN001_zpsbe5432e7.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/FANJIGAMDFAN001_zpsbe5432e7.jpg.html)
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/FANJIGAMDFAN003_zpsa70fb5dd.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/FANJIGAMDFAN003_zpsa70fb5dd.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 08, 2014, 07:34:03 PM
Needless to say, there was a lot of clean-up, filing, and sanding required to get the fan into any kind of presentable shape. It looks pretty ragged in around the actual solder joints, but the blades are really solidly attached and the hub area will be hidden by other components when this is assembled. Only the blades will be visible.
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/FANJIGAMDFAN006_zpsd6c4ed39.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/FANJIGAMDFAN006_zpsd6c4ed39.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 08, 2014, 07:37:17 PM
This is what the fan will look like when mounted in the protective ring that goes around it, with the hub which supports the shaft bushing setting in front of it.
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/FANJIGAMDFAN004_zps90c8fd9b.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/FANJIGAMDFAN004_zps90c8fd9b.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 09, 2014, 04:07:47 PM
I'm done to the point where I need to make up the shroud that surrounds the fan. I have the outer rim from mild steel, and the hub from mild steel. I have some 1/16 #316 stainless steel for the 3 "spokes" between the inner hub and outer ring, but I don't know whether or not I can braze it.---But I will in about 10 minutes. Fortunately the piece I have is quite large. I will snip off a couple of pieces and conduct a test.
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 09, 2014, 04:36:01 PM
And the answer is--The 316 S.S. can be brazed or silver soldered equally well. In the picture, the part on the left has been brazed using oxy acetylene and flux coated brazing rod. The item on the right has been silver soldered with the paste flux being applied to the joint first. The silver solder seems to flow out better, requiring less clean-up after the fact. The brazed joint had a lot of small "welding berries" around the main weld, which required clean-up with a grinding disc.---Which is fine when working on automotive car bodies, but not really desirable for model work. So, my question is answered. I will use the 1/16" stainless steel for my spokes and silver solder the joint. That is a good thing, otherwise I would have had to go down street and buy some 1/16" mild steel material.
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/BRAZING-SOLDERING001_zpsd018a51e.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/BRAZING-SOLDERING001_zpsd018a51e.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 09, 2014, 04:55:26 PM
This is going to be one of those situations where the jig to hold the pieces in alignment for silver soldering will be as complex as the soldered assembly. The central hub must be held concentric to and parallel to the outer rim, and the 3 "spokes" will be set at 120 degrees apart. Fortunately, the "jig" is mostly lathe work with some accurately placed holes. The position with 4 blue posts is the actual soldering station. The other two positions are intended to let me turn the part in the jig and maintain the 120 degrees between spokes.--In fact, looking at it as I post this, I probably only need one of the double post stations at 120 degrees to the main "soldering" station.
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/SHROUDJIG_zps96e95cfb.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/SHROUDJIG_zps96e95cfb.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Allen Smithee on July 09, 2014, 05:39:44 PM
A silly question - why not put a centrifugal fan on the flywheel hub and duct the fan efflux onto the cylinder fins with some sheet-metal shouds?

On the questiopn of suck vs blow - blow is better because you're more likely to direct the stream of air where it is wanted, whereas a suck-through system would need cowlings around the cylinder fins to ensure that the air isn't just being dragged in from all directions.

0.03 supplied,

AS
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 09, 2014, 06:37:36 PM
Allen--I agree 100% about your take on the suck versus blow issue. As for why I didn't add a fan to the flywheel hub and add a duct--the ductwork would hide too much of the engine.---Brian
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 09, 2014, 10:06:59 PM
That all went surprisingly well. The jig was a lot of work, but it held everything located very well. I didn't even bother removing the soldered parts from the jig, just set all 3 spokes in place (all of the locating pins were in the jig) and put enough of a tack at each end of each "spoke" to hold everything solid. Then I removed the shroud from the jig and tacked everything on the back side, then went around and soldered everything solid. It was more work cleaning it up afterwards than it was doing the soldering. I didn't get too crazy with the clean-up, because the shroud is going to get painted flat black when all of the brackets are soldered onto it.  This pictures shows the jig, the shroud, and the fan, from the front side.(The side facing away from the cylinder.) and one shot from what will be the side facing the cylinder..
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/FANSTUFF001_zps4b88fd08.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/FANSTUFF001_zps4b88fd08.jpg.html)
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/FANSTUFF002_zpsaa6fe3d5.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/FANSTUFF002_zpsaa6fe3d5.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 09, 2014, 10:10:36 PM
These two shots show the fan in the shroud, on a dummy shaft from the front and from the rear. The fan does not contact the inside of the shroud when the shaft is rotated. (Big sigh of relief!!)
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/FANSTUFF003_zps432cf457.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/FANSTUFF003_zps432cf457.jpg.html)
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/FANSTUFF004_zpseb560696.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/FANSTUFF004_zpseb560696.jpg.html)
Title: Re: Cooling Fan for model I.C. Engines
Post by: Brian Rupnow on July 11, 2014, 02:49:42 PM
This morning was show down time. I had finished the shroud and brackets for the fan yesterday afternoon, and painted the shroud. This morning I got up and added some set-screws to the fan hub, and made up a shaft and pulley for the fan. I was very fortunate in finding a rubber o-ring of the correct length, and the fan was installed on the engine. I am very pleased with the results, and the 2" diameter six bladed fan which is travelling approximately at twice the engine speed puts out a very noticeable breeze over the cylinder cooling fins. The engine exhaust is a bit smoky, because I was running some two cycle oil with the naptha fuel to provide lubrication for the Viton piston ring.--The oil to fuel ratio is 1:20, but I think I can safely cut that back to about 1:35 for future runs. The engine has a wet sump and splash lubrication of the con rod big end.
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