• Advertisement

thermatic fan upgrade or not?

New Users (or anyone else) is/are welcome to ask questions in here to which the answers might be obvious to most but you simply don't know yourself or are unsure where to find the answer. You can also ask questions about the working of the forum or anything else you may think of.

Moderator: MAN 16.242

Forum rules
### This section is a NO FLAMING ZONE! That means you cannot reply "harshly", abusively, sarcastically or in any negative manner to members. ###

thermatic fan upgrade or not?

Postby bagmaker » Wed Sep 30, 2015 7:19 pm

Hi all
considering changing the standard set-up for multi-thermatics (2 x 12" + 2 x 14" -four fans total)
This will do away with a couple of loooong vee belts, idler, pulleys etc, hoping to improve power and fuel, warm-up times, vibration, etc
TD101 pancake volvo rear mounted.

Can anyone advise the pro's or cons of changing?

Cheers
bagmaker
 
Posts: 12
Joined: Fri Jun 26, 2015 10:09 am
Has thanked: 0 time
Been thanked: 3 times

Re: thermatic fan upgrade or not?

Postby DiAmOnD T » Fri Oct 02, 2015 12:48 am

Honestly I don't think you will find any noticeable "power" increase and I would hazard a guess that fuel consumption if changing for the better would not even equate to 1 ltr per 100km.

But would love to know if you do change it and find that it does increase power and reduce fuel
The Diesel Guy
- Mobile heavy vehicle repairs serving Sydney to Newcastle -

dieselguynsw@gmail.com
User avatar
DiAmOnD T
 
Posts: 976
Joined: Thu Oct 07, 2004 2:11 pm
Location: under the subway at 'the main
Has thanked: 1 time
Been thanked: 24 times
Favourite Vehicle: AEC Mandator Ex Browns no7

Re: thermatic fan upgrade or not?

Postby qbb469 » Thu Oct 08, 2015 3:18 pm

Engine driven fan takes 15+ kW.
Thermos and a big alternator take about 2.5kw. Requires about 7x400w fans. Keep an eye out on the 2018/19 volvos they'll have thermo setup.
qbb469
 
Posts: 4
Joined: Tue Oct 06, 2015 11:04 pm
Has thanked: 0 time
Been thanked: 3 times

Re: thermatic fan upgrade or not?

Postby rustbucket » Fri Oct 16, 2015 4:59 pm

We have done this, it is not for the faint hearted.
First, had Davies Craig calculate on makers data how much HP to drive the original fan, the figure is definitely between 10 and 16% ! Huge for a small spec 6V92T
So we fitted 4 x 14" but used the high performance DC ones as they have the 16" motors in them.
Next we added a supplementary radiator from a Ford V8 EA I think was the model, from ebay with 2 fans and shroud and ran the 12v fans in series.
We also fitted 3 x thermal switches so the 2 banks on the original radiator and the supplementary could all be set at different temps to turn on.
As well as getting the original radiator cleaned and making a very close tolerance shroud for it.
Performance was not good enough so had a custom radiator made from PWR ($1700) and made an aluminium shroud for it, as well as fitting 2 x 16" DC thermatics
Also used coolant with no anti freeze, works way better.
So now I am pretty happy, just came through a hot central NSW 17 tonnes plus, with 4 tonnes of trailer on the hook, sitting on 80 deg C at 100 kph.
One other modification I have made is to be able to switch the power from the cranks (alt supplied) to the house (solar supplied)
The house Lithium bank runs at 27.5 v so they run that little bit faster if running off them
We have 3 Kw of solar to top them up, or a nominal 90 amps @ 24 v coming in when the sun is high. All banks of fans running is 50 amps.
Yes, you can feel the difference when you take the 3 banks off the alt at once, if for instance you are slogging up a hill, there is just that slight bit of a jump when you take the load off.
Do not expect thermatics to do what the old fan has done, do the figures and you will need to get somewhere close or you will be doing a lot of night driving.
Next step will be water mist injection into the intake after the air cleaner, amazing difference when you get a bit more humid air in there for combustion
BTW we get about 3 k/litre, dunno if that has changed as we did this as part of the conversion
William
User avatar
rustbucket
 
Posts: 35
Joined: Tue May 13, 2014 4:34 pm
Has thanked: 0 time
Been thanked: 11 times

Re: thermatic fan upgrade or not?

Postby bagmaker » Wed Oct 21, 2015 9:05 pm

Thanks for that rustbucket, you have gone a long way on the cooling route. I have looked over the web build of VP and as you say, not a light project to modify.
A couple of things are interesting, first kudo's for the side discharge idea, I had wondered about the airflow at the back of these buses, I am pretty sure its not going the way most people beleive. "Sucking" from the rear through the side sounds a much better idea.
Also, 10- 16% is a lot for a fan of a 320hp motor, 40 odd horses. Mine (about the same power Volvo- allegedly) is driven by 2 off "A" section belts (each about a million miles long) so IMHO my fan wont be drawing over 15hp maximum without them squeeling little bits of rubber and smoke off. They are in good nick so I question that figure.
I might hang off for a bit more research

Cheers for the replies
bagmaker
 
Posts: 12
Joined: Fri Jun 26, 2015 10:09 am
Has thanked: 0 time
Been thanked: 3 times

Re: thermatic fan upgrade or not?

Postby rustbucket » Thu Oct 22, 2015 7:37 am

No worries Baggie,

I use CPF Detroit Specialists in Brissie. When I mentioned to Cameron who is their 2 stroke expert that Davies Craig had worked out that the fan consumed in excess of 10 % he just said, "that's right"
So I would expect that 15 HP may be a tad on the light side ? After all we are talking about having to remove around the same amount of heat energy that is created to produce around the same amount of go.

I think that you have it back to front as to where we pull air from though, again this was done with design advice from Davies Craig.
Both radiators have a grille on the outside that has the louvres set at 45 deg to the direction of travel. Air is drawn in through these by the thermatics, assisted by forward motion and exhausted through the large grilles in the rear engine door, and for all we know, maybe some under the bumper bar, though I would think it unlikely.
I would not want to blow already hot air through the radiator, from the engine compartment, and it does seem to get away easily enough.

Another thing is that belt drive is pretty inefficient, you are probably losing another 3-4 HP there that would not be the case for a direct drive.
We originally had belt drive, driving the huge Horton fan that was fitted when VP was built, if the belts are adjusted correctly they will drive it with no squealing.

See if you can find the specs of your fan, you will need to do this anyway if you are still considering thermatics, as you need to get somewhere close to moving the same amount of air, to have effective cooling.

Coolant can also play a huge part, we have gone to one without glycol as used by BCC bus fleet (don't need much anti freeze in Brissie) and I think this alone is worth another 5-10% in cooling efficiency (and lots cheaper too) Only downside is you have to buy 200 ltrs, which didn't worry us as VP capacity is now around 70 ltrs.

The only way to get back the energy required to remove the heat energy from the coolant is to use a different, free energy source. That is what we have done with our solar, when we are humming along on a hot summers day and all three banks are running, there is abundant energy from the roof to drive them. If we have to drive for hours at night, we simply switch them to the cranks and cop the loss of power.
Cheers
William
User avatar
rustbucket
 
Posts: 35
Joined: Tue May 13, 2014 4:34 pm
Has thanked: 0 time
Been thanked: 11 times

Re: thermatic fan upgrade or not?

Postby bagmaker » Sat Oct 24, 2015 8:38 am

Your right, William, I did have your theory around the wrong way.
And I think (unqualified) that I still prefer my way, sucking through rear facing side louvres from the engine bay and out through the side, thermatics assisting if required.
I appreciate that the air temperature would be warmer going through the radiator but the overall cooling capacity is the same as you are cooling the engine block one way or the other.
My Volvo has a larger intake area than a tourmaster (checked one out yesterday) but the radiator is probably about the same size with my fan being 670mm diameter-I am not sure how the two motors compare with heat output / efficiency.
My estimation of power draw came from an old limit in my head that an A section belt will give around 5hp. I checked the net and it figures that is closer to 5kw (old-timers disease) transmitted under best procedure so the fans are at the top end.
Using this link you can figure what is available http://www.mymachineinfo.com/2015/04/ca ... ssion.html and yes, 3-4 hp loss through the belts is probably about right too.
IMHO 40hp is too much for 2off "A" section belts, you would see them falling to bits quicker than they are. 30hp may be closer to the mark. As stated by both of us, maximum cooling capacity is only a part of the reason for changing to electric fans.

I didn't notice the rig getting particularly hot on my delivery trip Rockhampton to Victoria but then again, I don't want to ever notice it. I wonder if other members know a history of overheating with DD Volgrens?
Also my way is cooling the engine compartment a little more, handy if you are sleeping over it that night : :?
All that said, its just elementary at this point, I wont be doing anything straight away, too much other stuff is lined up in front of the fans. :roll:

Kudos to the great build of VP William, nice website
bagmaker
 
Posts: 12
Joined: Fri Jun 26, 2015 10:09 am
Has thanked: 0 time
Been thanked: 3 times

Re: thermatic fan upgrade or not?

Postby qbb469 » Sun Jan 24, 2016 12:18 am

How does your setup cope with sitting on the retarder?
Have you added additional alternator power?

So doing the math your mechanical 670 mm fan was chewing 10-16% of crank HP.
Given the better efficiency on just a belt to thermo conversion. The bcc three belts to a long shaft to 2 belts and a fan system would be even less efficient.

Certainly has me thinking now.

What power are your fan motors?
How loud are they?
qbb469
 
Posts: 4
Joined: Tue Oct 06, 2015 11:04 pm
Has thanked: 0 time
Been thanked: 3 times

Re: thermatic fan upgrade or not?

Postby qbb469 » Sun Jan 24, 2016 2:44 am

http://kth.diva-portal.org/smash/get/di ... TEXT01.pdf

Link about fans for those interested.
qbb469
 
Posts: 4
Joined: Tue Oct 06, 2015 11:04 pm
Has thanked: 0 time
Been thanked: 3 times

Re: thermatic fan upgrade or not?

Postby bagmaker » Sun Jan 24, 2016 8:13 pm

interesting link there QBB, thanks for posting
now my eyes are bleeding :D
I had never considered pusher fans on a radiator -believing that pulling the air through gives a more uniform flow throughout the area of the radiator.
As indicated in section 5.1, pusher fans are around 24% more efficient due to the density of cooler air they move.
Every day is a school day.
Disappointed that not much mention was made about radiator positioning, options on positioning and airflows around the bus but realistically, the author only had one london bus to play with

Again, thanks
bagmaker
 
Posts: 12
Joined: Fri Jun 26, 2015 10:09 am
Has thanked: 0 time
Been thanked: 3 times

Re: thermatic fan upgrade or not?

Postby qbb469 » Sat Jan 30, 2016 1:17 pm

Having the fan in the back sucking air from the side then dumping it in the vacuum behind the bus is about 15% more efficient than front mount.

Manufacturers size cooling systems via the temperature to boil method. Basically run it on a dyno In a wind tunnel then ramp the air temp up until it boils. Then calculate the heat rejection from there.

Radial radiators are a lot more efficient as well. no dead air flow spots. But that's getting into the experimental arena.

Air flow wise, approximately 15% of drag comes from air flow underneath the bus, 30% from drag behind the bus, 25% from frontal area. There's a lot of papers on it around the web.
qbb469
 
Posts: 4
Joined: Tue Oct 06, 2015 11:04 pm
Has thanked: 0 time
Been thanked: 3 times



  • Advertisement

Return to New Users/Ask a Simple Question

Who is online

Users browsing this forum: No registered users and 1 guest