ESE's works engine tuner

[Frits Overmars]

Frits, would you think that modifying an air cooled barrel to be cooled with oil would be better than air? if your engine rules spec "no WATER cooling allowed," and not "no LIQUID cooling allowed"?

Yes. But unlike the four-stroke Suzukis that carried a lot of oil anyway, you could choose something more cooling-effective than oil. Glycol, for example.
However, chances are that the rules do not allow other cooling fluids than water, on the basis that spilling some of the stuff on the track could render the track unusable for quite some time (which is also the main reason for not allowing diesel).

[Ns1Montesa]

Didn't old Rotax square cylinders basically have water around the whole outside of cylinder?

I know this is ineffective because of. Let's say stale water movement?

Regarding completely covered transfers. Sachs used pretty big water jackets in the 80s for their 50 and 80cc engines.

But as jonny already sad. Low water movement. Dont know what kind of goal they followed with this huge amonunt of water around the bore.

cheers

[Muhr]

What you need is RSA125 manuale_ingranaggi_conici_2010_rev3.PDF , but I see no options of uploading PDF files here, so I copied the relevant pages for you, Muhr.
The conical gear is a sliding fit on the balance shaft. It is keyed into position with a 2,5 x 3,3 mm needle, # 9 in the center drawing, and the assembly is locked by the nut that also clamps the left-hand balance disc.
By the way, did you notice that the direction of the inlet disc rotation in your drawing is opposite to that of the RSA?

I'm preparing to send off for the manufacture of axles and gears, which feels pretty ok. What I don't feel really comfortable with is the lubrication for the bearing closest to the disc valve.
In the pictures you sent Frits, it looks like the distance pipe has a swirl that will take the oil up ?? (nr6)
The options here might be to run full ceramic or a closed bearing.

[TZ350]

[breezy]

is it me or other than not having holes for the wrist pin in these pistons the ring could be pinned in a standard piston through the crown and caps fitted in the wrist pin holes..... or am I missing something...

[husaberg]

ior am I missing something...

Summer, cold Beer, decent governance and your former empire

[SwePatrick]

is it me or other than not having holes for the wrist pin in these pistons the ring could be pinned in a standard piston through the crown and caps fitted in the wrist pin holes..... or am I missing something...

Not having wristpin holes in piston is making it possible to run extreme exhaustports without shortcircuiting to the crankcase through the wristpin into the transfers.

[breezy]

Not having wristpin holes in piston is making it possible to run extreme exhaustports without shortcircuiting to the crankcase through the wristpin into the transfers.

yes i understand that issue.....but sealing caps in the wrist pin holes would surley do the same job.... i think now that the continuos piston ring has been abandond this is an expensive way of doing it...now im fully awake, probably a maintanace issue with just removing the piston ring would be difficult...

[breezy]

Summer, cold Beer, decent governance and your former empire

Yes husa, pubs are closed... out of work...nothing wrong with Boris... who could possibly vote for Corbyn....yes the old empire cinema has finally gone....have we missed anything

[Pursang]

Regarding completely covered transfers. Sachs used pretty big water jackets in the 80s for their 50 and 80cc engines.

But as jonny already sad. Low water movement. Dont know what kind of goal they followed with this huge amonunt of water around the bore.

cheers

I suspect the main reason for those jackets was to create a even temperature to maintain dimensional stability of the cylinder, rather than heat dissipation.

The issue with low flow or thermo-syphon cooling is the occurrence of nucleate boiling at the hot spots.

Boiling water/coolant creates vapour bubbles (steam) on the contact surface. Vapour does not have the thermal conductivity of the liquid coolant.
That point gets hotter and hotter...........

One of the advantages of a high flow system is that the movement of the coolant brushes off the bubbles as they form.

I would like to experiment with a cooling system using some of the highly thermal conductive products used in electronics, for example.

The ideal would be a gel that increases its conductivity with temperature rise. Even temp all round the entire cylinder.

Cheers, Daryl

[trevor amos]

Steady on Nigel, things could get a lot worse especially if the `orange one` cons the supreme court and ends up with four more years , god help the world!

Does anyone see any heat transfer problems with the screwed together piston, lots of different sections in there that will expand and contract at different rates? In the event of a bad seizure how is the piston removed, just thinking.

Trevor

[husaberg]

..have we missed anything

Its not all bad though, you top the field for Horse burgers and cheese that smells like foot odour.....
Seriously though how is it going there

[ken seeber]

Does anyone see any heat transfer problems with the screwed together piston, lots of different sections in there that will expand and contract at different rates? In the event of a bad seizure how is the piston removed, just thinking.

Trevor

In terms of heat transfer, I think they’ll be ok. Why? There is a lot of sectional contact between the crown/inner piece and the outer skirt, by both the thread and shoulder. With the crown piece having the male thread, this will expand and lock into the skirt female thread, hopefully providing the good necessary contact and also preventing any flogging out and even unscrewing. It was not this way 12 months ago.

The pistons are inevitably & relatively heavy due to their 2 piece construction. Possibly a concern at the 19k rpm.

Seizures, what a negative consideration. Yep, might be hard to access the pin for removal. I guess that’s why the man invented cordless 5 inch angle grinders.

Either way, it is interesting and good on him/them having a go.

[breezy]

Its not all bad though, you top the field for Horse burgers and cheese that smells like foot odour.....
Seriously though how is it going there

well Husa, i suspect that every body is having the same kind of issues... not knowing whats next up the road is worrying......3 recessions and now a pandemic, what ever next?: war!..

[mantonakakis]

In terms of heat transfer, I think they’ll be ok. Why? There is a lot of sectional contact between the crown/inner piece and the outer skirt, by both the thread and shoulder. With the crown piece having the male thread, this will expand and lock into the skirt female thread, hopefully providing the good necessary contact and also preventing any flogging out and even unscrewing. It was not this way 12 months ago.

In one of the recent videos, it appears that until the threads are fully tightened, there is significant play between them - the two pieces of the piston can "rock" relative to each other (and presumably have some noticeable radial clearance - I'm sure Alex will drop in to clarify). Seems like a relatively simple countermeasure - maybe use selectable shims to set the ring to ring land axial clearance, and either add a more sizeable cylindrical interface with a close radial fit, or tighten the fit if such a feature already exists. My imagination tells me that radial clearance between the two pieces might be the biggest concern, i.e. if the O.D. of the crown is not concentric to the O.D. of the skirt once the pieces are tightened together, some bad things will happen...

Alex, if you do drop in here, if you share a cross-section view of the two pieces of the piston, I'm sure we can provide some feedback/sanity checking re: heat transfer and clearances/tolerances! (Not doubting your/Mark's design decisions, just offering more eyes to double-check or maybe come up with some design improvements).

The pistons are inevitably & relatively heavy due to their 2 piece construction. Possibly a concern at the 19k rpm.

I think I saw Alex mention somewhere recently that they weigh about the same as conventional pistons...