ESE's works engine tuner

[Muhr]

I can understand that you want to dynamically balance a crankshaft with cast surfaces. but balancing a fully machined crankshaft? I'm having a hard time understand what new information might pop up just because you start spinning it, with a counterweight that has a geometry that does not resemble anything you will put on the pin.
but I might have missed something

As Dave said if you can balance it in the engine it would be another thing.

[lodgernz]

Ball-park .
If you can persuade your exhaust pipe to shove 38cc of washed-through fresh mixture back into the cylinder before the exhaust closes, you'll have a winner.
Of course even the washed-through mixure will not be 100% pure, but a long, narrow exhaust duct helps in this respect; it will provide for a small-area contact plane between the spent and the fresh gases. But while mixing is limited, the long, narrow tract offers an unfavourable ratio between duct volume and duct wall surface, thus increasing the heat transfer from the walls to the mixture.

Thanks again Frits. I plan to water-cool as much of the extension as possible, so that might help.

However, your reply makes me wonder if I really need that much volume in the exhaust duct.
I'm using Wobbly's suggested duct length of ca 2 x bore. Do you know if this is based on some factor other than duct volume?

[lodgernz]

I've been so far unable to find any good info on small end bearings, so I hope someone here can give me some advice.

In my 97cc engine I plan to use a piston that has a 14mm pin, with a rod that has a 17mm eye. This requires a bearing with 1.5mm needles, which I have been able to source, with silver cage.
Ignoring for the moment the inadequacy of the rod, is there any reason that needles this small might have a problem at 14,000RPM?

[Pursang]

Attachment 334782Attachment 334783

Bike is off for the winter, no conclusion yet, before the spigot had been in thin mild steel welded to the exhaust

More information, (from a fire engineering not automotive site).



At the sort of temps we are working with in the exhaust duct, the thermal conductivity of S/S and carbon steel approach each other.
Still leaves S/S the (temporary) advantage of a shiny, radiation (heat) reflective surface.

At lower temperatures a significant difference, suggesting S/S expansion chambers are more likely to retain heat in the body.

Eagerly awaiting the results of Wobbly's tests with ceramic matrix, thermal coatings.

Cheers, Daryl

[TZ350]

I've been so far unable to find any good info on small end bearings, so I hope someone here can give me some advice. 1.5mm needles, is there any reason that needles this small might have a problem at 14,000RPM?

As a comparison. What diameter are the needles in those high reeving 50's that have 10 and 12mm LE pins, could they have needle bearings with needles as small as 1.5mm Dia?

[nine-thirtysix]

Do you guys think it is possible for a experienced welder to weld the exhaust duct without dimensional damage of the plated bore?

I consider to let weld the duct of my CR125 cylinder. The duct has a average length of 50mm and on the floor I would like to fill it up up to 12mm away from the bore.

I was thinking about putting a aluminium mandrel in it but may be the heat transfer is not good enough....


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[Frits Overmars]

Do you guys think it is possible for a experienced welder to weld the exhaust duct without dimensional damage of the plated bore? I consider to let weld the duct of my CR125 cylinder. The duct has a average length of 50mm and on the floor I would like to fill it up up to 12mm away from the bore. I was thinking about putting a aluminium mandrel in it but may be the heat transfer is not good enough.

I agree about the heat transfer of a mandrel. As for the welding, personally I would not risk a good cylinder without prior proof that the welder is capable of doing it.

[SwePatrick]

Weld near cylinderbore, i don´t dare do it,

But is there material enough to mill a slot and insert a billet piece of aluminium and lock it tight with some fasteners from underside?
Then when in place, shape it as you want.

[jonny quest]

TZ350, do you have a fuel pressure regulator on your EFI system? What pressure do you run, and what is the pressure swing?

[peewee]

Do you guys think it is possible for a experienced welder to weld the exhaust duct without dimensional damage of the plated bore?

I consider to let weld the duct of my CR125 cylinder. The duct has a average length of 50mm and on the floor I would like to fill it up up to 12mm away from the bore.

I was thinking about putting a aluminium mandrel in it but may be the heat transfer is not good enough....


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im just a pretend welder on Saturday and sometimes sunday but even if you use large heat sinks on the top and bottom deck and something in the bore, I have a lot of doubts whether you can maintain the exact dimensions of the pre-welded bore. of course I have been wrong thousands of times before however. you can try it, worst case is youll get some distortion (probly the little dividers between transfer windows and possibly the skirt near the bottom) and just strip the plating and over bore it slightly, then replate slightly thicker to get back to original bore size

also I wonder if the weld heat will cause some other problem with the plating ?

[lodgernz]

As a comparison. What diameter are the needles in those high reeving 50's that have 10 and 12mm LE pins, could they have needle bearings with needles as small as 1.5mm Dia?

My 50 and the 80 from which my 97 is developed, both had 12mm gudgeon pins in the same 17mm rod eye, so needles of 2.5mm diameter. No problems revving to 14,000.

I'm just wondering if the smaller contact area of the 1.5mm needles will increase the pressure on the eye and the pin, like stiletto heels do on a carpet compared with flats.
I'll certainly be doing checks after every meeting for a while.

[Grumph]

My 50 and the 80 from which my 97 is developed, both had 12mm gudgeon pins in the same 17mm rod eye, so needles of 2.5mm diameter. No problems revving to 14,000.

I'm just wondering if the smaller contact area of the 1.5mm needles will increase the pressure on the eye and the pin, like stiletto heels do on a carpet compared with flats.
I'll certainly be doing checks after every meeting for a while.

I'd think they'd be OK. When you consider the angular swing of the rod versus the circumference of each roller, the 2.5mm rollers don't do as many revs in that swing. The 1.5mm rollers may actually cover a longer area - and should change direction easier too.

But I'm prepared to be shot down....

[lodgernz]

I'd think they'd be OK. When you consider the angular swing of the rod versus the circumference of each roller, the 2.5mm rollers don't do as many revs in that swing. The 1.5mm rollers may actually cover a longer area - and should change direction easier too.

But I'm prepared to be shot down....

Thanks Grumph. I wouldn't shoot you down, but I'll post here when it's proven one way or the other.

[Grumph]

Thanks Grumph. I wouldn't shoot you down, but I'll post here when it's proven one way or the other.

I've since refreshed my memory and Irving quotes INA using 1.5mm rollers in both big ends and small ends back in the 60's. He says no problem using 10 plus...
Smaller and lighter is said to be a plus for small ends.

[lodgernz]

I've since refreshed my memory and Irving quotes INA using 1.5mm rollers in both big ends and small ends back in the 60's. He says no problem using 10 plus...
Smaller and lighter is said to be a plus for small ends.

All good. Thanks again.