G'day, you might find petrol engine pistons too light for a diesel. Remember diesels run 17:1 or more compression, I doubt pitbike ones will stand the stress. Everything has to be heavier as a result. 2 Stroke diesels also use an exhaust port in the barrell, only one valve for an inlet. Might be easier to go petrol with the thing!
Cheers,
Stork
60mm diameter Pistons
Agreed 100%, which was why I was asking as well. If going diesel you probably want heavier duty pistons with longer skirts to handle "piston rock" at higher compression ratios that diesels need for compression ignition. I agree with stork955 in relation to the pitbike pistons no being up to the task for a diesel engine. If it "must" be a diesel, I think a diesel generator piston (to get one that small) may be the answer, however I don't know what they cost.stork955 wrote:G'day, you might find petrol engine pistons too light for a diesel. Remember diesels run 17:1 or more compression, I doubt pitbike ones will stand the stress. Everything has to be heavier as a result. 2 Stroke diesels also use an exhaust port in the barrell, only one valve for an inlet. Might be easier to go petrol with the thing!
Cheers,
Stork
Hi Stork,
From the research I have done on the 2 stroke diesels you have got it wrong way around. Slots are machined into the liner just above the bottom of the stroke where air is forced in and as the piston starts to rise the single or double exhaust valve opens to expel the exhaust then just under 1/2 way up the compression starts then close to top dead centre the injector is activated and the explosion happens then the piston goes back down to repeat. ( still have to more research on this too as to air injection and the exhaust valve opening and closing and at what stage of the rising piston)
I did send the ebay seller a Q about what the pistons are made of and they are alloy pistons so they won't be any good. In the corner of my shed I found a 75mm od shaft from a gearbox and I do know it would be good quality steel so at a crunch I can use that to make my own pistons and just buy the ring kits from that ebay seller.
Anyway I'll be finishing that bathroom in the morning then I won't start another one until tuesday so finally got some time to work on it but as it's raining everyday I may only get one full day out of the shed batteries then the next day I will be running off a genset while the I recharge the batteries. I never bothered setting up a backup genset/charger for the shed bank as with the solar and the 1.5kw motor conversion wind genny I made provides enough power to keep the batteries charged thru the week.
Cheers Bryan
From the research I have done on the 2 stroke diesels you have got it wrong way around. Slots are machined into the liner just above the bottom of the stroke where air is forced in and as the piston starts to rise the single or double exhaust valve opens to expel the exhaust then just under 1/2 way up the compression starts then close to top dead centre the injector is activated and the explosion happens then the piston goes back down to repeat. ( still have to more research on this too as to air injection and the exhaust valve opening and closing and at what stage of the rising piston)
I did send the ebay seller a Q about what the pistons are made of and they are alloy pistons so they won't be any good. In the corner of my shed I found a 75mm od shaft from a gearbox and I do know it would be good quality steel so at a crunch I can use that to make my own pistons and just buy the ring kits from that ebay seller.
Anyway I'll be finishing that bathroom in the morning then I won't start another one until tuesday so finally got some time to work on it but as it's raining everyday I may only get one full day out of the shed batteries then the next day I will be running off a genset while the I recharge the batteries. I never bothered setting up a backup genset/charger for the shed bank as with the solar and the 1.5kw motor conversion wind genny I made provides enough power to keep the batteries charged thru the week.
Cheers Bryan
I'm starting to have a rethink about the cylinder liners now and I'm thinking a hydraulic ram or 2 may be the go, already polished bore so no real honing needed. A quick lick in the lathe so get a good surface finish on the OD then shrink a heatsink casting over the liner tube. As you guys have stated I will need to use a longer piston and the youtubes I have seen on 2 stroke diesels do have a lot longer cylinder liners than I'm machining. Ideally I would like to have atleast 100mm stoke so may be time go go on a hunt for some donor hydraulic rams.
With the crankcase I can go for a larger liner too and this would ramp up the 989.1 cc I worked out before too.
I'm glad now I started this thread as I can change the things as needed but the front cover with the bearing arrangement can stay so I can that finished. The main shaft will come thru the the housing and have a keyway to hold the spider bearing so I can get that side all finished.
So this weekends job will be finish the front cover then make the front seal cover so I can have the bearings all set with the correct pre load. For testing all I will have to do is add a shim or 2 to give a tad of end float so the bearings run free and that will help on the final balancing. If time permits I'll get the main output shaft in the lathe too and get it under way.
Pic's will come but that iphone I have the only way to transfer pic's is by email and that can take ages to go thru but pic's will come soon guys...
Cheers Bryan
With the crankcase I can go for a larger liner too and this would ramp up the 989.1 cc I worked out before too.
I'm glad now I started this thread as I can change the things as needed but the front cover with the bearing arrangement can stay so I can that finished. The main shaft will come thru the the housing and have a keyway to hold the spider bearing so I can get that side all finished.
So this weekends job will be finish the front cover then make the front seal cover so I can have the bearings all set with the correct pre load. For testing all I will have to do is add a shim or 2 to give a tad of end float so the bearings run free and that will help on the final balancing. If time permits I'll get the main output shaft in the lathe too and get it under way.
Pic's will come but that iphone I have the only way to transfer pic's is by email and that can take ages to go thru but pic's will come soon guys...
Cheers Bryan
G'day, you are right, the inlet is in the barrel. I dunno what I was thinking there...I should also add that you need a supercharger to make it work. There is very limited overlap to get the exhaust out. Usually 2 stroke diesels are low speed so it is not as big an issue. (Low speed = around 1500 rpm max).
Cheers,
Stork
Cheers,
Stork
Anyway weekends gone and was too busy with other jobbies so didn't get a chance to work on the engine. Today I machined up flange to hold the 400mm saw blade I have here which I'm setting up to cut upto 3" branchs. As the fire season is almost over this spring when I get time I'm cutting a heap of firewood ready for next season to make a few extra $$$$. Basically used a 1" bright bar shaft and the flange and retaining plate was machined out some offcuts I had here. Put a 6mm keyway in the bore the hardway by going back and forth in the lathe and kept kicking myself for being too lazy to make the slotting attachment.
One night this week I will need to finish machine that liner I got in my big lathe as I will need it to finish the shaft for the saw. This sawwill get powered from the PTO off my 48hp fiat tractor so power wont be an issue but still gotta make the flat belt attachment for the tractor yet.
All good fun and once I can get some 1/2" air line that old pneumatic press I got will be coming back to life, that old baby would flatten a stubbie cap at 15psi too so image what it will do with red hot steel when the conrod forging needs to be done.
Cheers Bryan
One night this week I will need to finish machine that liner I got in my big lathe as I will need it to finish the shaft for the saw. This sawwill get powered from the PTO off my 48hp fiat tractor so power wont be an issue but still gotta make the flat belt attachment for the tractor yet.
All good fun and once I can get some 1/2" air line that old pneumatic press I got will be coming back to life, that old baby would flatten a stubbie cap at 15psi too so image what it will do with red hot steel when the conrod forging needs to be done.
Cheers Bryan