@carryfast serious question, what does the blower (air pump) do and where does the compressed air go?
There are two ways to use the 15 speed, dependant upon the situation. Bare in mind, this gearbox was popular when 350 was considered big horsepower. Thats when five deep reduction gears were preferred over the single gear in a 9 or 13.
If a 90 ton gross mass truck is going to lift off on a long uphill, start in deep reduction 1, shift progressively 2,3,4,5 when the road offers an opportunity tho shift up next gear is low 3 from there on same as a ten speed. The other way is when low gears are only needed to get the truck rolling, deep reduction 1, 2, 3 low 1,2 etc.
Deep reduction is very handy when making up a road train. The lowest and highest gears in a 15 OD are respectively lower and higher than in a 13 OD. @les_sylphides the advent of 13 and 15 speeds precedes my practical awareness, so i cannot offer any enlightenment on which one came first. I do recall as a schoolbor in the early 70s reading in the truck classifieds, trucks fitted with with 17 speed RoadRangers. I assumed in hindsight that these were replumbed 13s.
Before horsepower hit the stratosphere, here 15 speed RoadRangers were the most prolific, beeing particularly versatile with its five deep reduction gears.
In the USA ten speeds seem to be the default 'box, a 15 without the deep reduction gears, understandably in a country where loads are considerably lighter.
@les_sylphides you are probably aware that on the earlier versions of the air switches, deep reduction could (not should) be engaged in the high box.
My mate sold his Western Star to a shonky local bloke. He was paying the truck off in cash, but my mate wasnât letting it go until the final payment had been made. Consequently, the truck sat in his back yard, just as heâd reversed it in in deep reduction. The shonky one sent it to auction less than a week after taking delivery, complaining that it couldnt get to 80kph.
The idiot didnât know about the deep reduction switch on the dash. My mate had âofficial proofâ that it could do at least 112kph.
How many members can Carryfast hold an argument with at the same time without actually understanding what he is arguing about?
Answers on a postcard, please, to:-
Mme Fifiâs Asylum for the Delusionally Insane,
Bedlam House,
Barking (Mad),
Norfolking Sense
Ironically this topic could be one of the best ever posted on tnet.A combination of meeting of minds in which me and SDU might finally find some common ground and in which even maybe old protagonists like gingerfold and anorak and bewick could find common ground in the idea that at least a Gardner 8LXB and 9 speed Fuller would have been a miles better all round combination than an 8v71â N and â15â speed Fuller.
The fact that a drawbar trailer would be the only way in which a mobility scooter could pull a useful payload speaks for itself well done SDU.
Except itâs not a 5 over 5, itâs a 5 over 5 over 5.In which 3 of the low range 5 ratios match the mid range 5.As opposed to just reducing the 2 lowest ratios in the mid range to the point where thereâs no need for the effectively 2 speed low range.
How does the high pressure exhaust supposedly flow into the inlet when the inlet ports are still closed by the piston at the point when the exhaust valves open and effectively up to the point when the exhaust gasses have evacuated the cylinder leaving behind a relatively lower than atmospheric pressure environment in the bore which draws in the new charge of air, helped by the blower.
Yes the exhaust valves stay open a bit longer after BDC into the compression stroke slightly before the inlet ports are closed again by the rising piston, to aid that process.But the exhaust gasses themselves do most of the work.
You might have missed it but a non turbocharged N series Detroit means naturally aspirated.The exhaust gasses drive the turbocharger.
Not the exhaust gasses, driven by the blower, drive the turbocharger.There is no higher than atmospheric ( forced ) induction pressure, unless itâs turbocharged.
Exhaust pressure doesnât spit back through the inlet side just like it doesnât on a 4 stroke.
Would it help if I told you that the exhaust valves open at around 70 degrees before BDC compared to less than 30 degrees before BDC on a 4 stroke.
Well before the piston uncovers the inlet ports.The exhaust gasses are well on their way out of the exhaust valves before the inlet ports are open.The exhaust valves are held open a bit longer after BDC in slight overlap with the inlet ports at which point the gas flow is all going one way at great speed out of the exhaust and into the inletThen the exhaust valves and inlet ports are shut.Add a turbocharger or two to that weâre in business until the bureaucrats spoiled the party.
Firstly itâs not an air âcompressorâ.Itâs just there to augment and compensate for any shortfall in the scavenging effect in the cylinder from the explosively evacuating exhaust gasses going out of the exhaust valves to atmosphere.The net effect is natural aspiration when the inlet port is opened by the descending piston.
The charge being drawn in by the combination of scavenging and blown in by the blower enters the inlet ports in the cylinders via the air chambers within the cylinder block around the bore liners.Which do a similar job as a 4 stroke inlet manifold.
As for the Fuller 15 speed v 13 speed itâs a difficult call but the 13 speed seems to be in the ball park with around 12.5:1 in L to 8.3:1 in 1st, 6.2:1 in 2nd and 4.5:1 in 3rd.
I think I get how the 15 speed ( and 20 speed Spicer ? ) would be better suited to Australian weights and terrain looking at the numbersâŚ
As I said at the beginning of the conversation and Franglias has not disputed. Both of us knew this was classified as a naturally aspired engine, as indicated by the N in various engine designations.
Frangers asked a simple question about turbocharging and accepted the answer, but you hooked on to that, deriding his gap in knowledge, consistently making condescending remarks.
Lose the attitude and stop trying to prove you know more than everyone else and twisting other participants input, especially when it is supporting your stance. Accept that thereâs always going to be someone who knows more than you, about some subjects, and weâre on the way to interesting conversations.
Yes. The gases flow out because they are at a higher pressure in the cylinder than in the (approx) atmospheric pressure in the exhaust.
Yes.
Yes, because of the pressure difference in the cylinder and exhaust.
If the inlet is also at atmospheric pressure then why will the gases not flow equally into both exhaust and inlet?
The gases are GASES. They are not a solid piece of matter. Just because some gas flows out it does not âpullâ the rest of the gas with it.
Which is why
is nonsense.
How is it that the âhigh pressureâ gases rush out, and leave a partial vacuum behind?
They only flow when there is a pressure difference. If there were a partial vacuum then the gas would flow to fill the low pressure area.
All Detroit diesels have mechanical super chargers on them. They choose to call them âblowersâ. And they choose to call these engines NA, or naturally aspirated, presumably to distinguish them from those which have mechanical and turbo charging.
No it doesnât.
Why doesnât it? Because the inlet is at higher than atmospheric pressure.
If it was at the same atmospheric pressure as the exhaust, then when the inlet valves are open, and the inlet port exposed, why would the high pressure gases not flow equally through both these ways?
The gas has no âknowledgeâ of where it should flow to please an engineer. It is not following a bit of gas that went before it. It is being acted on by pressures, and with higher pressure in the cylinder it will flow to lower pressure areas be it through a simple valve or open port.
It is not at all like on a 4T.
Yes I found it difficult to see that turbo charging would work in any sort of 2T engine. It is the problem of filling the cylinder with fresh are to burn, at the same time as emptying it of burnt exhaust gas that is an issue, and using a turbo must make it harder for the exhaust gases to exit.
I do now accept that the gain is more than the losses.
Less of an issue on 4T.
I donât know anything of 2 strokes in commercial applications, just a warm recollection of kickstarting just one more time til it goes, and that mad rush when the power comes, so briefly, on song.
I watched this video, first of a series, from a guy called Dave, who I think is another fine example of Australian expertise on the subject.
Cheers for that link. Good stuff.
Being a description of a typical motorcycle etc type engine, the charge is pushed into the cylinder (under pressure) by the piston descending into the crankcase.
This is not the same as the Detroit and other larger 2T diesels which have oil in the crankcase to give better lubrication and longer life.
The expected life of a smaller petrol 2T engine, and that expected from a commercial size 2T diesel is rather different.
In smaller engines the new charge is under pressure in the crankcase, and hence pushed into the cylinder, and in the Detroit types it is under pressure from some sort of super-charger.
To be fair Franglais clearly thought that the exhaust gas flow and evacuation was entirely dependent on the blower.He also seems to have missed the fact that the piston and inlet ports play the same role as the inlet valves and inlet ports of a 4 stroke.Stopping any reverse exhaust flow into the inlet side.
He also wrongly assumed that the exhaust flow wasnât more than capable of driving a turbocharger unlike a 4 stroke.
So 8v92TA with a 15 speed Fuller looks like a good bet for the Australian market at least by the standards of the day.
The mobility scooter and trailer looks like what the average retired NZ driver would rightly use to collect the shopping and DIY.
A 5 over 5 over 5 range change box just as you said yourself Ro.
Looking at the numbers I think I get how progressively shifting through all 5 gears of the âdeep reductionâ ( low ) range would probably do a better job of getting a road train moving from rest and building some momentum for the change into whatâs usable of the mid range and then high range.Especially on loose soft surfaces and deep bull dust.
Than the low range of a 9 or 13 speed.
As for the Detroit two stroke natural aspiration by the combination of the charge being mostly drawn in by exhaust scavenging and blown in by the blower.
Unless itâs turbocharged.Then not only does the outgoing exhaust draw in the new charge of air behind it it also drives the turbocharger providing proper forced induction to the process.
The mobility scooter, coupled to a 40t drawbar trailer, without it overloading the scooter, is the definition of the advantages of train weight v combination weight.
No, itâs not to be fair, itâs you mitigating your bad behaviour to yourself.
There was no need for your rudeness and condescending attitude to Frangers, especially as you, yourself dont fully understand the role of the blower and workings of a Detroit two stroke engine.
What stops the exhaust gases from flowing into the inlet?
The gases will flow into a lower pressure area.
You have said that the exhaust gases have power, enough to drive a turbo-charger.
Q. Where do they derive that power from?
It is because they are at more than atmospheric pressure that they have energy/power.
If they are at more than atmospheric pressure, then if the inlet is at atmospheric pressure then they will flow into the inlet. That is why the inlet needs to be above atmospheric pressure.
The engine needs to be supercharged to function.
Yes, blown in by the supercharger.
The exhaust gases do not âdraw inâ anything. They are above atmospheric pressure, as demonstrated by them being capable of driving a turbocharger.
They drive the turbocharger by being above atmospheric pressure, and forcing their way past the turbine.
Finally! During the course of this conversation I was referred back to a thread that was active before I found this forum. On that thread you wrongly assumed that a 15 was a splitter. Multiple contributors corrected you and explained why you were wrong.
I, myself had this discussion with you,quite some time back, again you chose to argue the point, insisting that it was a splitter.
This is the third time, to my knowledge, that you have contrdicted and argued with people who have hundreds of thousands of miles experience, when you have never even seen the 'box, let alone used one.
Your comprehension skills are sadly lacking, judging by you twisting of words and misquoting the proletariat with real
experience and expertise. It is not unreasonable to conclude that your level of comprehension is similarly employed in your googling endeavours, attempting to show youâre the cleverest cookie on TN.
Just be the real Carryfast, not the expert in every subject, Carryfast you are so desperately trying to project. Who knows, you may even come off premod. Free advice, take it or leave it.
