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Old 11-12-2018, 06:37 AM   #1
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Single Cylinderengine for AC compressor

I want to use a robin dy27 single cylinder diesel to drive the AC compressor.
The shaft runs CCW ( left). The AC compressor, a Thermo King X430 runs clockwise. It has an internal pump and can not be reversed.
If I turn the diesel engine around and make a shaft on the flywheel / cooling fan side then all is good.This robin has a ball bearing at the flywheel side and a sleeve on the out put shaft side. The rope pull starter part can be removed because it has an electric start provision.


Has any one made a successful modification with a pulley on the flywheel side?


Thank you, J
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Old 11-12-2018, 07:40 AM   #2
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maybe the solution is to use a different compressor.. the sanden enhanced HD7 series(there are HD7 and enhanced HD7) compressors are much smaller in size but would provide the amount of cooling you are looking to achieve. if i remember right you are planning to belt-down the compressor to gain more torque and reduce capacity with some of the fans removed or shut down.



-Christopher
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Old 11-12-2018, 08:21 AM   #3
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Thanks Chris, I thought about that but the cost to open up the system, get all the adapters and refill it are not something I look forward to.
May be later when I have the stuff to make it a reversing heatpump so that I can use it for heating as well.
The other thought would be to replace it with an electric compressor and attempt to put that onto the roof as well.



If someone would pay some money for the whole thing I would not mind pulling it of the roof and changing into a split heatpump.


The shaft modification on the diesel is for know the preferred solution. Since I can do it myself and that takes times but is not expensive.


Later johan
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Old 11-13-2018, 10:04 AM   #4
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I wouldn't run it off the flywheel side. Reason being is that the "sleeve" bearing that you mentioned isn't pressure fed, and will usually burn up in short order if you have any type of one-directional load on them.

If the engine is running ccw, and the compressor is running cw, would you be able to rotate the engine 180 on the vertical axis, therefore making the engine shaft run cw? I mean, if it is electric start, accessibility to the flywheel shouldn't be required for operation.
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Old 11-13-2018, 10:14 AM   #5
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Quote:
Originally Posted by joeblack5 View Post
The rope pull starter part can be removed because it has an electric start provision.




Thank you, J
I have owned a handful of generators that had electric start.

Every one of them had a pull start for backup. At some point I needed to pull start every one of them.

I would recommend keeping yours.

Good luck with your project. I think that is a great idea.
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Old 11-13-2018, 12:57 PM   #6
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Thank you both for the response. I did not explain my dilemma very well.


The way the AC compresor sits it the bus leaves me only with the diesel engine next to it.








So if I were able to mount the engine inline with the compressor then all would be good. The CCW engine and the CW compressor would match because they are facing each other.
But I do not have the space to move the compressor. Besides that I need a 4;1 or 5;1 reduction ratio. So with a 3000 rpm motor the compressor should run 600 RPM. That would also match the power of the motor to the demand of the compressor and the amount of cooling capacity I need.


To reduce the radial load on the bearing I would use a HTD timing belt.


So the flywheel side has a ball bearing, the normal shaft side has a sleeve. This engine has a oil pump but I do not know if that output bearing is pressure fed. Need to study the robin DY27 manual a little more .


Steve, I do not like take the pull start of but I feel that I have no other good option. I hear you Murphy is listening as well...



The above test in the pictures uses a DC permanent magnet motor running there at 36 Volt. There is some notable cooling..That motor would be replaced with the Robin diesel.


Johan
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Old 11-13-2018, 01:35 PM   #7
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Not knowing the dimensions of the motor you're planning to use and not being able to really discern the amount of space available, would something like this work? I'm sure you've given this a lot of thought, but sometimes I feel like a simple solution is easy to overlook
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Old 11-13-2018, 01:52 PM   #8
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I think you should read the manual again. How I read it, it has the ball bearing on the flywheel side while the pto side has a babbit bearing.

If that is the case, I see no problem in mounting a standard v-belt pulley on flywheel end. The engine is air cooled so make sure that whatever you mount onto the flywheel, that it doesn't disrupt the cooling air flow. The "guards" and other sheet metal surrounds are important too so keep them intact.

You could use a htd belt, but I don't think it's necessary and would just add more expense.

Another thought that I have is you could add one of those manual winding pull start pulleys onto the pto end, and then you would have your pull start option as well. Just make sure you get one that winds the correct way(ccw I believe).

Good luck with it.

ON EDIT. I read your 1st post backwards. Most small engines have the "babbit bearing" on the flywheel side with the ball bearing on the pto side. I know that a babbit bearing isn't supposed to have much load on it unless it is pressure fed, which is why on your 5hp briggs and strattons your not supposed to run anything off the flywheel side.
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Old 11-13-2018, 02:32 PM   #9
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Thank you both. Yes that would be easiest , thank you for the sketch, a picture is a thousand words, but there is no space unless I would move the compressor more to the front of the bus. I looked into flipping it 180 degree but it does not work with the existing freon lines.

The robin dy27 came originally of a generator. So it did not have radial loads on the sleeve bearing.

Thank you for letting me look into a pull start mechanism on the PTO side. Indeed that should not be to hard. Even just a pulley with a rope could do it if in a pinch.

I will try to modify an old brake caliper as adapter and spacer to get over the flywheel nut. . have to look for an old e350 caliper and see if that would work out.

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Old 11-19-2018, 08:44 PM   #10
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Set the motor strait forward as in the sketch and run a jack shaft between the motor and compressor. It would require 2 belts but they would be short
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Old 11-20-2018, 02:54 AM   #11
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I think you may want to rethink the use of that particular engine.

A single cylinder engine, even if mounted on a lot of cushioning, is going to hammer you senseless every time it goes down on the power stroke. At 3000 RPM's that means it is going to fire 1500 times a minute if it is a four stroke or 3000 times a minute if it is a two stroke. The sound of the exhaust can be minimized but the pulsing of the power stroke is going to be very difficult to negate.

I also do not think that engine is going to be large enough to turn that compressor under full load. Most coach companies figured that the A/C compressor stole 35-50 HP when fully operational. Part of the load factor was in turning the fans on the condenser and evaporators. But the major part of the load came from the compressor.
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Old 11-20-2018, 03:20 AM   #12
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I think you may want to rethink the use of that particular engine.

A single cylinder engine, even if mounted on a lot of cushioning, is going to hammer you senseless every time it goes down on the power stroke. At 3000 RPM's that means it is going to fire 1500 times a minute if it is a four stroke or 3000 times a minute if it is a two stroke. The sound of the exhaust can be minimized but the pulsing of the power stroke is going to be very difficult to negate.

I also do not think that engine is going to be large enough to turn that compressor under full load. Most coach companies figured that the A/C compressor stole 35-50 HP when fully operational. Part of the load factor was in turning the fans on the condenser and evaporators. But the major part of the load came from the compressor.
I think he is planning on isolators ? If the compressor is mounted to thebus engine Id bracket the pony engine to the main engine which outs it on the motor mounts .. his plan is for low rpm run of the compressor as the bus is insulated. You flow less air over the evaporator and the txv will take care of the reduced compressor rpm. The charts looked right a couple pages back on his pulley-down of the compressor. 5-6 horsepower o think was the final number needed
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Old 11-20-2018, 04:05 AM   #13
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I think he is planning on isolators ? If the compressor is mounted to thebus engine Id bracket the pony engine to the main engine which outs it on the motor mounts .. his plan is for low rpm run of the compressor as the bus is insulated. You flow less air over the evaporator and the txv will take care of the reduced compressor rpm. The charts looked right a couple pages back on his pulley-down of the compressor. 5-6 horsepower o think was the final number needed
Christopher
Christopher you know a whole lot more about HVAC that I do. What I know I can usually write it all out in crayon on my thumbnail.

Since that compressor is exactly the same as used in HVAC installations in commercial buildings I know the electric motors that run them are substantial. Like upwards of 15+ HP electric three-phase motors.

I am not sure exactly how you could pulley down the compressor enough to do the job and still only use 5-6 HP. I would think that the first time one of the unloader valves unloaded it would stall the engine. Or the compressor would be turning so slow as to not be able to load the unloader valves enough to unload to make the compressor load.

I might be wrong but it was my understanding that A/C compressors work a lot better turning fast than slow. Which accounts for why the A/C doesn't work very well in motorcoaches when the coach is in stop and go traffic and the engine isn't running very fast.
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Old 11-20-2018, 06:47 AM   #14
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Christopher you know a whole lot more about HVAC that I do. What I know I can usually write it all out in crayon on my thumbnail.

Since that compressor is exactly the same as used in HVAC installations in commercial buildings I know the electric motors that run them are substantial. Like upwards of 15+ HP electric three-phase motors.

I am not sure exactly how you could pulley down the compressor enough to do the job and still only use 5-6 HP. I would think that the first time one of the unloader valves unloaded it would stall the engine. Or the compressor would be turning so slow as to not be able to load the unloader valves enough to unload to make the compressor load.

I might be wrong but it was my understanding that A/C compressors work a lot better turning fast than slow. Which accounts for why the A/C doesn't work very well in motorcoaches when the coach is in stop and go traffic and the engine isn't running very fast.



the A/C compressor is just a pump, it is true iots capacity is higher the faster you spin it.. (thus as you mention why coaches run high idle when parked in summer to keep the cabin cool)..



Johan is insulation his bus and has determined that he needs nowhere near the original capacity of the system as installed by the manufacturer.. a city bus A/C is designed to keep the bus cool inside full of people in a broiling downtown city with both doors opened and closed every block.. and with the engine at lower RPM's..



for a coach that will be insulated and travelling doors closed or parked most all the time not nearly that is necessary.. by pullying down the original piny engine. to run the compressor somewhere in the 700-800 RPM range, the charts show he can achieve the required capacity of the system.



at the other end to still be able to move humidity, he is reducing the amount of air being blown over the indoor evaporator coil.. thuis even with reduced compressor capacity will allow the TxV to regulate refrigerant flow.. all thats important is that the compressor runs above its published minimum RPM (generally to facilitate oil movement in the refrigerant circuit).. other than that its all about moving heat..



by spinning it slower and geared down from the pony engine speed, the actual torque applied to the compressor drive is increased..



you are right, horsepower is horsepower. but he is not trying to aschieve the full HP rating of that compressor.. if he were then yes that little engine that could... couldnt.
-Christopher
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Old 11-20-2018, 07:54 AM   #15
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thanks guys, ... Yes Brad, you are right. with the hammering. It is not the best but the combination of lack of space, cost and availability resulted in this engine.
the AC compressor is mounted on its own cradle separated from the engine and chassis. If you look careful at the image with the Dc motor and V belt then that is visible. We are not planning on running this often , just in extreme cases.

It is also going to run a DC generator / motor So that I have a backup in case our solar / battery is not performing.



As Christopher said, I hope I need only 12 to 15KBTU to cool this bus. At least that is the number I used.

That equals about 4 HP. The performance graph of the X430 shows about 600 to 800rpm for that amount of cooling. Hence the 5:1 ratio to get the motor in a reasonable RPM range



My gamble and experiment is that the larger evaporator and condensor coil result in a high efficiency.



Thanks Coondog for your input. I am in a pinch for space, an extra shaft and bearing will throw me off 4" or so.


I have not made any further progress on this part. Today I will stop at the junk yard and see if I can find a suitable piece of steel to help me out.


Later J
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Old 11-21-2018, 09:24 AM   #16
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If the bus is insulated, the small engine will be fine for providing comfort. Reefer units use about 30hp to keep an entire semi trailer frozen.

A double-sided toothed belt and two idler pulleys will allow you to reverse direction if you mount the engine next to the compressor with the output pulley facing aft.

Or mount the engine with the output pulley facing forward and put a shaft with pillow block bearings under the engine to get back to the pulley of the compressor.

BTW: Thanks for inviting us for a meal and interesting conversation in your Elf bus dining room the other day.
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Old 11-21-2018, 02:52 PM   #17
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A double-sided toothed belt and two idler pulleys will allow you to reverse direction if you mount the engine next to the compressor with the output pulley facing aft.

Or mount the engine with the output pulley facing forward and put a shaft with pillow block bearings under the engine to get back to the pulley of the compressor.

Those are both great ideas! Pillow bearings and 3/4" keyed shaft are easy to find and work with.
I wasn't even aware that double sided timing belts existed! Cool find..

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Old 11-21-2018, 08:36 PM   #18
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Thanks guys,


I had looked into the double sided belt. The pulleys I have are HTD Metric 10 pitch and indeed I can not find them in double sided for HTD pitch 10 MM.


The shaft under the engine might work. Will take a look at it tomorrow.


Although at this moment with all the brainstorming it looks like I should not have an axial load on the original PTO side. In the original direct drive generator application there was not axial load at all.



Today i spend some decent time at the junk yard hunting for useful parts. Not really lucky but got some pulleys from Ac compressors.



Jazty Nice job on that veggie centrifuge.


Alpine, it was fun, how did your projects go?


Later Johan
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Old 11-22-2018, 08:22 AM   #19
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Thanks guys,


I had looked into the double sided belt. The pulleys I have are HTD Metric 10 pitch and indeed I can not find them in double sided for HTD pitch 10 MM.


The shaft under the engine might work. Will take a look at it tomorrow.


Although at this moment with all the brainstorming it looks like I should not have an axial load on the original PTO side. In the original direct drive generator application there was not axial load at all.



Today i spend some decent time at the junk yard hunting for useful parts. Not really lucky but got some pulleys from Ac compressors.



Jazty Nice job on that veggie centrifuge.


Alpine, it was fun, how did your projects go?


Later Johan
Not much progress on my box truck conversion while I put in a lot of time at the property I am going to sell. However, my neighbor rebuild the interior of his sailboat and did a beautiful job with the woodwork. I got a lot of useful tips and local suppliers from him. Will post the results once I start building my 'galley' unit containing sink, stove/oven, and drawers. That is a nice winter project I can do indoors.

If you are concerned about loads other than torque on the output shaft of your little diesel engine, you can always connect it via a Lovejoy coupling to a short shaft rotating in pillow bearings that will take the radial and axial loads.

The Hatz and Farymann engines I used in the past had specs showing what loads were allowed on the output ends. I assume that Subaru has similar info available.
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Old 11-22-2018, 08:27 AM   #20
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Jazty Nice job on that veggie centrifuge.
Thanks Joeblack. It's been a long and slow process getting that thing together. I've only been able to tinker with it for a couple hours in the past few months. It's getting there, though! A direct drive centrifuge would have fewer technical hurdles to overcome, but this centrifuge is the one I have.

I still need to make the air separator for after the scavenging pump and install the flat plate heat exchange. Then it's time to test for real! If it works I'll clean it all up.

One thing I'd like to change is to use a hydraulic pump to power the whole thing off of the engine instead of the electric motor. I can eliminate the faster moving chain drive that way and direct drive the waste oil pump. It's extra complexity for this stage, though.
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