ESE's works engine tuner

[andreas]

A 180* Tandem with same crank rotation would need an intermediate gear - just to make it work that way.
But balance wise , it would mean that when the crankwheel counterweights were at TDC/BDC they would form a rocking couple , just like a Parallel Twin @ 180.
Then when at 90* the two out of balance counterweights ( any number less than 100% BF ) would both be facing opposite each other ,forward or backwards - cancelling the horozontal resultant.
The intermedate gear needs to be the same size as each crank gear , making it too big to drive the clutch - and a balance shaft off that gear cant kill the rocking couple , as its in the same plane.
Thus another small gear is needed to drive the clutch - result is no advantage over a concurrent firing Tandem , but an extra power consuming gear/bearings , and less big bang tyre grip.

Ok, thanks Wobbly. I'll have to ponder this.

[teriks]

What have i missed with dlc coating.
Diamond like coating, Why coat the whole rod?

You specify where you need a functional coating, and if you need any surface masked.
The rest, well.. it gets the black stuff apart from where its supported.

Why not make an aluminiumrod with inserts for the needlebearings?
And no,, they won´t breake if using new tech, old alurods had a lifespan.
But new alloys make them way wey more reliable.
Watched a guy on youtube that had them in his engine for 9 years and none of them breaked.(1000+ Honda engine)

What alloys are those?
Asking for a friend that's changing aluminium rods every 30min runtime to hopefully avoid developing sudden new 360deg intakes..

[Condyn]

Going back to Vanniks write up including contact discontinuities. While developing pipes for vintage engines (1970s) I have often times drifted in a certain direction, even while raising the target rpm. The pipe gets longer than the factory configuration. I notice the HP going up. But being that the pipe is growing in length, is this a T-bone guarantee that my diffusers are too efficient, creating more short circuiting adding to the smearing effect and further eliminating the boundary between gas temps?

[andreas]

Going back to Vanniks write up including contact discontinuities. While developing pipes for vintage engines (1970s) I have often times drifted in a certain direction, even while raising the target rpm. The pipe gets longer than the factory configuration. I notice the HP going up. But being that the pipe is growing in length, is this a T-bone guarantee that my diffusers are too efficient, creating more short circuiting adding to the smearing effect and further eliminating the boundary between gas temps?

If I recall your last entry, it was somewhere along the lines of " how can the exhaust pulse that is responible for drawing a certain amount of fresh charge up and into the pipe be able to push the same amount back in again, when it has been weakened by friction and losses in the reflection".If this is how you intended the question, don't focus too much on the contact discontinuty, but look at how the original pulse branches into one decompression wave in the diffuser and the remnents of that pulse eventually becomes the compression wave.

Why the pipes are longer even though the engine speed is higher- more information needs to be presented, but I don't think stronger diffusers is the guaraneed cause of it.

[wobbly]

Condyn , I think there are two effects going on in your situation.
Firstly , yes , " overscavenging " as Mr K Kanemoto called it , by having overly fat mid , and therefore overly efficient diffuser sections causes increased shortcircuiting
and thus a smeared , longer , larger volume of mixed raw and burnt fuel.
But secondly in your older ( I am assuming ) single port exhausts , you cant use the huge effect a very restricted duct exit area can have on the efficacy of the discontinuity.

A single Ex port seems not to respond favourably to anything less than a 90% duct exit area.
Whereas a T or 3 port with a ton of Blowdown loves around a 75% restriction , to hit the magic Mach 0.8 number.

Edit - good example would be a LC 350 Yamaha racebike. Keeping the original scavenging system ( B ports up at 35* ) the best I could do was 66RWHP.
The next version had staggered timings ( A first ) and with modern radial and axial angles , 10mm fatter pipes - 20mm shorter , first dyno run was 77RWHP without adjusting anything.

[Flettner]

The most advanced twostroke in the world, well, perhaps just the most advanced TPI in the world. Anyway its been sitting outside under a cover for almost a year, bad me.
Finaly got excited about it enough today to sort the Ignitech out, found spark. Turned the LINK ecu off and fired it up using plastic bottle injection. Loud, but it runs, yay. Tomorrow get the LINK ecu working.

[TZ350]

.
Great work Flettner. Now for the EFI.......

[F5 Dave]

Yeah love to see an update on this.

Although dirtbikes are evil. Well mine is.

[SwePatrick]

You specify where you need a functional coating, and if you need any surface masked.
The rest, well.. it gets the black stuff apart from where its supported.
What alloys are those?
Asking for a friend that's changing aluminium rods every 30min runtime to hopefully avoid developing sudden new 360deg intakes..

As i understood then hone it away when setting bearing clearances, if so, why coat the whole rod, design only or does it make some sort of strengthening on the whole rod?
to me it´s just a coating to make for example wristpins withstand more wear and tear, it doesnt strengthen more then a couple of my on the surface, if even that.

I dunno about the alloy, i just know of peoples experiances, best in rc racing would be to buy a alu rod from one of the top producers, and you´ll have material for several rc rods

[Muhr]

If you add material to something that was not developed with the tolerances for this, you need to remove material either before or after, depending on what you intend with the application.
Do not think anyone has claimed that you apply and then remove on surfaces you want to apply on, however, in many cases masking is more expensive than just running the whole piece.

[Condyn]

Wobbly, have you always stuck with the ( many times ) sited percentages of header and diffuser lengths even while developing an older single port engine, or do these numbers no longer carry their importance?

I asked you several months ago if I should consider a TPO stagger due to the old school scavenging layout, and you advised me to test a few things as you were almost certain simultaneous opening was not ideal in my case. Unfortunately I have not had a chance to grind any cylinders for this project yet.

Even with the best possible efforts in grinding and welding, a vintage engine still poses the largest limiting factor, which is the overall casting. Realistically, I do not believe I will be able to stop all of the trapping efficiency issues with these old engines, that is why I am searching for logic as to what pipe characteristics should help the cause.

[Frits Overmars]

A 180* Tandem with same crank rotation would need an intermediate gear - just to make it work that way.
But balance wise , it would mean that when the crankwheel counterweights were at TDC/BDC they would form a rocking couple , just like a Parallel Twin @ 180.
Then when at 90* the two out of balance counterweights ( any number less than 100% BF ) would both be facing opposite each other ,forward or backwards - cancelling the horozontal resultant. The intermedate gear needs to be the same size as each crank gear , making it too big to drive the clutch - and a balance shaft off that gear cant kill the rocking couple , as its in the same plane. Thus another small gear is needed to drive the clutch - result is no advantage over a concurrent firing Tandem , but an extra power consuming gear/bearings , and less big bang tyre grip.

Seems like somebody forgot to tell Neil Hintz

[Frits Overmars]

If you add material to something that was not developed with the tolerances for this, you need to remove material either before or after, depending on what you intend with the application.
Do not think anyone has claimed that you apply and then remove on surfaces you want to apply on, however, in many cases masking is more expensive than just running the whole piece.

Are we still talking DLC? The toughest honing stones I know are diamond. And what did the D in DLC stand for? So if there are places where you don't want the DLC, masking seems the only option.

[lohring]

Big end bearings have been a weak link in our small engines as well. My article, Big End Blues, describes this. My favorite solution was from the late Jim Allen. He ran two rollers per retainer window. He used a very high strength heat treated maraging steel for his retainer. Pictures below.

Lohring Miller

[Frits Overmars]

Big end bearings have been a weak link in our small engines as well. My article, Big End Blues, describes this.

Lohring,
I was looking forward to an afternoon of reading pleasure, but I am unable to download your Big End Blues. All I see is an encouragement to download Adobe Flash Player, the most virus-sensitive software of the past 300 years.