Post by dieselguy86 on Apr 9, 2022 11:31:42 GMT -5
Your about right, 40mm is good for around .4 lb/sec mass flow. Using John's educated guess of 1 lb/sec for 50hp, you'll be pretty close to 20hp.
Your biggest headache will be figuring out the freepower unit.
I would go up to gt35 sized, you can find ball bearing ones cheap, pair it with an hp841 freepower unit and you won't have all that much invested, both time and money. Reason I say bb is because it takes alot less oil, and you have alot less oil heat to worry about. Having a bush turbo and freepower will need a good oil supply system when the oil gets up to temp.
For the freepower My original plan has been to use a 70mm turbo turbine and hot housing i have laying around. I dont know what i will use for reduction yet. 50k rpm would be about right i reckon. Maybe even an angle grinder gearbox, i think those motors rev very high. It might survive immersed in oil, as i say. Not figured out yet.
High speed gearing is a whole new world of problems , theres no point just having an oil bath as the gears will run "dry" at the speeds you're looking at , you need oiljet lubrication to penetrate the windage .
I'd use Joe's recommendation of the hp841 freepower unit , it'll save time and money in the long run