Serenity - 2002 Thomas HDX

[cadillackid]

Originally Posted by RHOMBUS

I guess I need to read more about it then. I am pretty confused now. Wouldn't all of the existing little ground wires from each and every light cause the "spider" effect and make a loop?

If I add several ground straps from the body to the frame, am I creating a ground loop then?

My thinking was that every piece of metal in the frame and body was basically a giant negative wire, with the return flow essentially taking the most direct route to the negative post of the battery, through bolts and welds and whatnot.

the little grounds on your lights most likely either go to the same wire in the harness running down the bus, or are simply short wires that are screwed to the body behind the bezel..

yes! make sure the body to chassis straps are solid.. on my old bird I only had a sinfgle electrical system.. it was a small bus..

there was a main large ground that came from the batteries (the batteries were tied together...) to the chassis..

from the chassis there was a ground to the engine.. and one to the body...

then there was a rear one to the body from the chassis.. (technically a loop could occur between the chassis but it still only had one oath to the main grounds..)..

ground loops affect mainly electronics... radios (noise and wierd amplifier issues).. computers.. (for engine, electrically driven needle gauges.. HVAC sensors.. (mainly in air conditiuoned busses).. electronic turn signal flashers.. cruise control...

rarely affected are heater motors and lights..


I dont know if yours is a dual system.. (some busses have a separate battery and alternator for the accessories.. like HVAC, Lights, radio, etc.. and another system for the running of the bus.. (gauges, engine control, transmission, engine fan clutch, computers..) ..

so yes fix your ground straps.. but dont run a separate wire from the battery to the body... strap the chassis to the body correctly..
-Christopher

[ArmyChap]

I'm confused, too. Electric is the biggest point of fear for me as I think about a skoolie... Because I know the least about it, and it's the greatest point for potential fire or traffic safety issues or just simple irritation.

Can one of you guys who's smart on this recommend a book on basic automotive electrical systems?

[QueSeraSarah]

I'm looking at shops for laser cutting... What's a good rate for sheet metal (off the roof)?

[Stu & Filo. T]

Originally Posted by cadillackid

the little grounds on your lights most likely either go to the same wire in the harness running down the bus, or are simply short wires that are screwed to the body behind the bezel..

yes! make sure the body to chassis straps are solid.. on my old bird I only had a sinfgle electrical system.. it was a small bus..

there was a main large ground that came from the batteries (the batteries were tied together...) to the chassis..

from the chassis there was a ground to the engine.. and one to the body...

then there was a rear one to the body from the chassis.. (technically a loop could occur between the chassis but it still only had one oath to the main grounds..)..

ground loops affect mainly electronics... radios (noise and wierd amplifier issues).. computers.. (for engine, electrically driven needle gauges.. HVAC sensors.. (mainly in air conditiuoned busses).. electronic turn signal flashers.. cruise control...

rarely affected are heater motors and lights..


I dont know if yours is a dual system.. (some busses have a separate battery and alternator for the accessories.. like HVAC, Lights, radio, etc.. and another system for the running of the bus.. (gauges, engine control, transmission, engine fan clutch, computers..) ..

so yes fix your ground straps.. but dont run a separate wire from the battery to the body... strap the chassis to the body correctly..
-Christopher

Was just discussing this with a ACFT R&E I work with, If you have ground wire from battery to chassie, then body to chassie your fine IF you run a ground wire from Battery to chassie, Body to chassie & battery to body then you have a ground loop and that's a no no

[thjakits]

You can ground the chassis, frame, body as much as you want - BATTERY NEGATIVE/MINUS.
You can run a separate wire for NEGATIVE back to the battery as much and often as you want, too - you are effectively "ensuring" proper ground/earth for each item you wire in....

Keep that in mind and you are "good".

HOWEVER to make things simpler, I would place GROUND-bars at strategic locations.

A solid copper bar with a load of connections on it. EACH bar would have a good size cable coming from a CENTRAL "bus cable" going back to the BATTERY NEGATIVE.
[OR - depending where your battery bank is and where your electric consumers are and where you want your ground-bars - you might want to put a loop around the perimeter of the bus and connect all ground-bars in a big series circle - ...and than of course the whole loop ONLY TO THE BATTERY NEGATIVE pole.]

Additional I'd add a short but good size cable DIRECTLY from the battery negative pole to the closest convenient chassis/frame/body part - if you already have the "central bus cable" or the "perimeter loop" this will only ensure that the frame/chassis/body is on the same ground as everything else - avoids static loads and galvanic corrosion. In this case the chassis/frame/body are not really conductors anymore (unless you use them for some small stuff), but you still want them on the ground/earth/negative pole.....

I'd add another 4-5 chassis/frame/body-grounds throughout the bus.....

Cheers,

thjakits

[dan-fox]

Excellent writeup, thjakits! Couldn't have said it better myself. Take it back to the battery.

[RHOMBUS]

Just about finished with the rear electrical box:


The box was rust treated, primed, and painted inside and out. All new bolts, new starter solenoid, stainless steel hardware in light duty areas, wires grouped, and all connections cleaned and received a light application of di-electric grease.


New oil pressure gauge with LED lighting element, new switches, new coolant overflow tank and the fuel filter and dryer hardware was rust treated, primed and painted to original colors. There are still 3 bolts at the bottom of the box that need to be placed, but that is proving to be a bit more difficult than I thought.

It's April and this month's task will be to get the entire air intake system completed. That's going to be a LOT of fabrication. I'll be hanging the actual filter assembly from the ceiling, but will have to run 4 bolts through it to the inside so it can be dropped for service. There just isn't another option. I'll make a little service panel and might as well route some wires through the panel as well.

[CaptSquid]

On the pressure gage, were you able to use the factory sender or did you have to replace that, too?

[RHOMBUS]

I just reconnected the wires to the new gauge. I found an exact replacement for the gauge. The oil pressure gauge worked before I took everything apart, so hopefully it will work again when I get the whole bus put back together.

[cowlitzcoach]

I hope your intercooler plumbing works the way in which you want it.

The problem as I see it is you are trying to suck air from a negative pressure area into a positive pressure area. It is going to require a lot of suction to overcome the negative pressure to provide air flow.

At slow speeds while going up a hill when the engine is working hard and the fans are working overtime to keep things cool it may work the way in which you intend it. But at highway speeds when the fans are not working overly hard I don't think it is going to be enough suction to overcome the vacuum that is in that area of the bus.

The air intakes on RE buses generally are plumbed through the roof for a reason--not only is it up and out of the dirt but it also is up and out of the low pressure area that is down close to the ground.

I think that if you have plumbed your intakes through the roof and angled then in a way in which they would have some ram effect from going down the road you would have a much better air flow.

I think the way in which you plumbed everything is very elegant and professional looking.

My only concern is it isn't going to work very well. Or at least it isn't going to work any better than what the original OEM design was.

[RHOMBUS]

Hey, cowlitz. Those air ducts are only to provide an extra avenue of fresh air to flow over the intercooler. I thought about the vaccuum at highway speed and there's just really no practical way I can measure the air flow to see if the intercooler will be getting any noticeable benefit. If the overall benefit is zero, it's still no real loss except for some time and money. This isn't for the engine air intake though.

The engine air intake system will still be in its stock location, pulling from high up on the passenger side of the bus. I did away with the Cyclopac air cleaner and am replacing it with a Donaldson air cleaner system, mounting it up against the ceiling of the engine bay. Then aluminum tubing from the turbo to the intercooler, and then all the way to the intake manifold. It's going to take a lot of precise measuring, cutting and welding to get it right. I'm too paranoid to try to draw engine intake air that low to the ground where the intercooler ducts are.

[RHOMBUS]

Also, one thing I don't really understand about the layout of the engine compartment is where the air goes after the fan has pulled it through the radiator and intercooler. The fan is within a couple of inches of the bay door, and that door is solid. There's the intake grate on the driver's side, and there's a grate on the passenger side. The only thing I can think is that the air crashes against the back door and then somewhat flows through the compartment to exit on the passenger side providing some minimal engine air cooling. I'd really like to make a grate in the bay door right behind the fan to get that air out of the bay, but not until I can be certain that the air isnt being used for indirect cooling.

[cowlitzcoach]

Remember the area behind the bus is another low pressure area. With the fan(s) creating a high pressure area inside the engine compartment the air will flow out the other side or down and out into the low pressure areas.

The major problem for all bus builders who build rear engine buses is how to cool the engine.

When the Series 50 engine was still in production I wanted to purchase a Thomas Saf-T-Liner RE with one. I thought a 350 HP Series 50 would be an ideal engine to get a bus up the hills around here without slowing down and still have enough HP left over to run a coach A/C system. Thomas would not even consider the option because of the engineering it would take to create a cooling system to do the job of cooling a Series 50.

[cadillackid]

dont some of the busses blow the air Outward from the radiator? maybe the turbo ones dont because of the intercooler?

I remember some city busses that the air into the engine bay was cowled up from underneath the bus into the engine compartment and the fan blew the air from the engine compartment over the radiator and out of the bus.. (not sucking it in over the radiator)...

if you had to you could "catch" the air for your intake and push it into the engine compartment for your intercooler...

-Christopher

[RHOMBUS]

cadillackid: I *could* put some kind of shallow hood scoop over those ducts to help grab the passing air better, and I may end up doing that. I just like the way the exposed inlets look. The scoop(s) in that area will be something a lot further down the road. I need to find a way to measure air that *could* pass through those tubes. Even if it's just a string with a camera looking at it. That way I could see if the Bernoulli effect of the air mass travelling along the body will work for me or against me. I'm hoping the air will want to conform, however slightly, to the contour of the inlets. The air will have 34 inches of travel to recover after being disturbed by the rear wheel flare. If it doesn't conform, it will do like cowlitzcoach said and create a sucking effect if the fan is off. Since the radiator screen starts about 5 inches after the inlets, hopefully the vaccuum there will be greater and still pull some air through, though it may not pass through the intercooler in that scenario.

[dan-fox]

If you want to get all scientific you could set up a water manometer pretty easily and actually get some numbers on where your bus sucks and where it blows.

[RHOMBUS]

LOL, Dan. I think it may suck and/or blow in the power to weight ratio and the rusted floor.

[dan-fox]

I am semi serious. Google "water manometer". Very simple to build; you just end up fixing open ended hoses here and there with masking tape to find out what the areas of high and low pressure are. Dead simple.

[thjakits]

Exactly how I see it!

Worst case you will have a stalled flow (...NO flow - in other words!)
The sides of cars, trucks, buses are ALWAYS low-pressure areas.

Actually this would be an excellent OUTLET area!

I wouldn't even wait around: Put a scoop on top of the 2 inlets!!

[Unless you can and want to re-route to the roof - and still you should put a scoop on the roof too! I would say - if you have a straight way up to the roof, it wouldn't be much work to cover the openings on the side.... do it now, where you are at it anyway!!]

thjakits

[Stu & Filo. T]

Originally Posted by thjakits

Exactly how I see it!

Worst case you will have a stalled flow (...NO flow - in other words!)
The sides of cars, trucks, buses are ALWAYS low-pressure areas.

Actually this would be an excellent OUTLET area!

I wouldn't even wait around: Put a scoop on top of the 2 inlets!!

[Unless you can and want to re-route to the roof - and still you should put a scoop on the roof too! I would say - if you have a straight way up to the roof, it wouldn't be much work to cover the openings on the side.... do it now, where you are at it anyway!!]

thjakits

That's what I did