[saamblr]

We are trying to convert about 50 numbers of non a/c buses in to a/c buses by installing a/c units with sub engine. ( we are located in Doha , Qatar).These are all TATA and Leyland buses. I am hunting for good a/c vendors and also trying to know more about the technical hitches involved. It will be great if fellow BHPian's can share their views / experiences on this.

[silversteed]

I'm seeing a lot of buses with Thermoking, Carrier and of late, Jingyi ACs. You can blindly opt for the first two, as these two constitute the bulk of the bus ACs found installed. Jingyi is a late entrant AFAIK. Costs less.

Regarding the slave engine, I do not know what the specifications should be, but I do know that small scale body workshops install the engines from scrapped Ambys and Jeeps. Perhaps reputed body builders like SMK, Veera Vaahana, Azad have their choices - probably smaller and better engines.

[getanilkhanna]

The idea behind the slave engine is to run the compressor for the air conditioner, The cooling unit is roof mounted and the best unit to run the show is the famous Carrier 110, the cost is approximately Rs 4 lac, however the cost of the engine is seperate.

The alteration required on an existing bus body is considerable as there has been no ducting for the air con vents or thermocol/ PU insulation in the inside, therefore the recommendation is to re build the bus body on the existing chassis.

The engine can be a conventional petrol or diesel engine depending upon your choice, the only disadvantage with the diesel engine is that it is nisy and will be heard inside the bus cabin.

The Air con compressor can be operated from the main engine, however it will put a lot of load on the engine thereby reducing the life of the engine,The Eicher 10.75 & the Swaraj Mazda engine's are more versatile and can easily bear the load of the compressor.

[Ashley2]

Are you sure of this conversion. Let me give my views
Air duct routing will normally be done through the pillars and then given to individual openings below the hatracks. This may require a heavy rework(almost replacement) of existing interiors. if this gets replaced then this should compliment with the seats. When you go for Air conditioning the seats should be atleast with a semi sleeper arrangement. I am not sure of the existing arrangement. If this is not available then it may look odd (though several buses are operated in this way too).
Then comes the air suction part in the roof. Here also the exisitng panels may get replaced. Now comes the final part the selection of slave engine for the AC. Plz check with the existing buses where its already installed for NVH levels. Several times the noise filteration into the saloon is vey high and it makes the passenger to feel that they are travelling inside a Generator Room. I felt really really bad this weekend when I came back from Coimbatore.
It was really a horrible experience. The noise of the slave engine is so loud that I am not able to sleep peacefully. coupled with this is the Tata LPO 1512's vibration. The chassis is a brand new one and it vibrates to the extent that even the seats (read as seat cushion) are not able to filter then.
So plz think twice before going for modification in the exsiting buses!

[saamblr]

There are many people doing this kind of conversion here. Sub engines are available from KIA , ISUZU and even from Mahindra. I have seen some of the converted buses. The quality of installation is substandard in many cases. Thermoking and carrier units are very very expensive. Even we have couple of TATA buses with factory fitted a/c units with sub engine. They are working quite fine. Mostly these vehicles run very short trips unlike Indian scenario.

[silversteed]

I think I get the picture. You need an airconditioned bus, but without most of the rather expensive creature comforts such as push-back seats with armrests and calf support, PUF insulation for soundproofing, adjustable vents etc. Correct?

If reliability is not too big an issue, you can consider Jingyi for the AC. They cost much less than Thermoking or Carrier. If the buses have a 160bhp+ engine, then I think you can drive the compressor from the main engine itself, though stopping for a long time would mean running the main engine and waste of fuel just for running the AC compressor. The advantage is the peace of mind of not having to take care of an additional mechanical device, ie., the slave engine.

I'm not sure if Tata produces buses with slave engines. They all have the AC compressor run by the bus' engine itself, AFAIK.

[drpullockaran]

Originally Posted by saamblr

These are all TATA and Leyland buses. I am hunting for good a/c vendors and also trying to know more about the technical hitches involved.

I am no expert but here are my observations:-

Please mention the torque output of the engines.

Is it for city use or Highway use and the average speeds expected with the expected number of passengers.

Find out if there is a way to increase torque output by tweaking the turbo unit.

You would have to use better quality engine oil and increase the frequency of oil change.

Shun the idea of using an auxiliary engine and if you are hell bent on it use a petrol engine to drive the compressor directly and not through a generator with a clutch assembly.

[saamblr]

silverseed, have you seen any buses with jingyi a/c ?. I have been talking to couple of vendors from china. What i understand is that if the engine is less than 230 / 240 hp , it will be difficult to fix the a/c without sub engine. TATA buses are about 140 / 150 HP. Leyland is about 170 HP i think. In both the cases , it will be difficult to install a/c without sub engine - especially in the Middle East where the temperature can go up to 50 degree plus !

[silversteed]

saamblr, I'm no expert with engines and ACs. What I tell you is purely based on my observations as a passenger. SRM Transports' AC sleeper coaches, some other operators' AC buses, mostly doing B'lore-Chennai or Chennai to other places trips were seen with Jingyi.

I'm sure these Leyland buses have a 177bhp or 205bhp engine (I think the older Medhadoota services from KaSRTC, built on AL 12M have 177bhp engines). They chug along well with ~38 pax (seater). For a seating capacity of 45-50 you will require a slave engine if the terrain involves a lot of ascents as these buses would feel strained with the AC compressor on all the way. If it's just highway cruising, then you can run the AC compressor off the bus' engine itself. I am not so impressed by the ride in TM buses.

[saamblr]

silversteed , the seating capacity of these buses are 65 pax. Mostly these are used for labour movement.

[silversteed]

And they would be required to cruise at 100kmph+ speeds, right? I guessed that, but underestimated the pax capacity. Then you should have 230bhp engines to drive the AC compressor off the main engine. Slave engine is a necessity in your case IMO, since you are converting existing buses to AC buses.

Why not check out with AshLey UAE? They have a plant there, and might be able to help you out with specs and options.

Experts, please comment... I ain't no expert

[BaCkSeAtDrIVeR]

Quite a few points have been already made.

First, you have to take into consideration power fo the existing engine; as far as possible, try to power the a/c unit from the main engine. This gyan comes from this forum itself.

Most important issue with regard to the slave engine mentioned here was maintaining the slave engine. IMHO, 3 cylinders or more is an overkill - try to find an engine which is as small as possible. Try to figure out the power consumption of the a/c unit and match it with the power of the slave engine (make the slave engine about 10-20% more powerful - to prevent overload and possible degradation due wear and tear). My guess is that 5 - 10 HP single cylinder will do the job. OTOH, the used car engines used in India for powering a/c units are originally rated 70 HP+.

If you can make this diesel powered, you will not have the headache of putting fuel meant for the a/c being poured into the tank for the slave engine's fuel.

Next, design and fabricate a good mount for that engine; which facilitates easy access and removal for maintenance. Apparently, people have difficulties maintaining the slave engines, and my guess is that it is due to lack of proper access to that. I suppose the slave engine drives a compressor, rather than an alternator. If you make the tubing of the compressor flexible, it should be possible to make a pull-out type mount which enables pulling out the engine for maintenance.

Smaller engines typically shorter maintenance cycles. For example, the AL 370 engine has service intervals of 7.5K with normal lubricant (we used servo 40); or 10K (with Servo `pride`/ castrol). The car engines have a oil change cycle of 5K kms. Remember that this engine is running at a constant speed, and there OUGHT to be a specification for service intervals in hours.

Go for the slave engine only if the main engine is not powerful enough to drive the a/c. 90% chances are that the main engine is nto capable of powering an a/c.

Considering that it is a cattle carrier, aesthetics would not be an issue, I presume?

What about sealing of joints and windows?

Much of the success depends on doing the interiors and the vents properly.

IMHO, you should go by local expertise on the matter of choice of slave engine and a/c unit. Thye ought to know better about availability of expertise for service and spares / maintenance back up available. Just a pointer - KIA, though well known and reputed internationally, is not heard of in India.

Originally Posted by saamblr

silversteed , the seating capacity of these buses are 65 pax. Mostly these are used for labour movement.

Point 1.

<growl>

I will call them cattle carriers. 65 pax in a 220 inch wheel base viking (the longest of them all) is still a cattle carrier, whatever you call it. What is the seating configuration? 3 x 4? eh?

</growl>

Point 2:-

Thank you on behalf of the people who travel in those buses for the small comfort you propose to provide them.

[Ashley2]

Originally Posted by BaCkSeAtDrIVeR

...
I will call them cattle carriers. 65 pax in a 220 inch wheel base viking (the longest of them all) is still a cattle carrier, whatever you call it. What is the seating configuration? 3 x 4? eh?

Its not a surprise. Here TNSTC Vilupuram with even 210" Viking(~10.5 meters) they are managing upto 59 and why not your Falcons(12 meters) with 65!

[saamblr]

The Isuzu diesel engine recommended by most of the suppliers is 4 cylinder 2700 CC .

Regarding the 65 seat capacity - this is nothing compared to 75 and 80 seat buses running in Saudi Arabia and UAE. One point need to be considered here. These buses are taking the labours from their place of stay to the work site and back. The distance travelled is as little as 3 to 5 KM in some cases.The average could be about 20 to 25 KM one way with the longest being 80KM. In India most of the city buses take almost 80 to 100 people ( including the standing passengers ) . Compared to this , at least these workers are getting a dedicated seat for themselves.

Most of the non labour class staff transportation is done using high end luxury buses or 30 seater mini buses like Nissan Civilian , Toyota coaster or Mitsubishi Rosa.

[ranjithrnath]

Hai Guys

Checkout this bus. MITHUN TRAVELS , a 36 seater 2x2 push back Contract Carriage Bus based in Kayamkulam, Kerala. KL-29-B-516. a 2004 model 132 PS AL Viking [non turbo model] with 202" WB. Originally registered in MH with Grand Coach.
Thus bus has a 4 cylinder MATADOR F307's engine to power the carrier compressor.The bus has a common diesel tank and while both engines are running, the mileage is only 3-3.5 km/l.