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Post by Johansson on Dec 12, 2014 14:32:42 GMT -5
Can you get the seller to remove the turbine scroll and take some pics?
As long as the turbine blades look ok I think it will do, fitting ball bearings to the shaft shouldn´t be a problem if you aim to keep the revs below 15.000rpm.
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mitch
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Joined: August 2014
Posts: 285
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Post by mitch on Dec 12, 2014 16:16:13 GMT -5
Forgot to mention this in the previous post, but should I find bearings to match the shaft OD and the bearing housing ID, I assume I would still need a thrust washer. The stock st50 with hydrodynamic bearings (actually bearing singular, I had a look at the bearing used in the st-50, pretty weird design!) acts also as the thrust bearing using oil channels to control the thrust, which would not be done with a ball bearing setup.
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Post by Johansson on Dec 12, 2014 17:05:31 GMT -5
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mitch
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Post by mitch on Dec 12, 2014 17:42:05 GMT -5
Johansson, thanks for the input, that was a very good idea! Is that an st-50 turbine wheel and shaft in the pictures you posted? And yes, the turbine blades looked okay, had a good amount of oil and dirt build up on them, and a very dirty turbine housing. Nothing I can't clean up I dont think.
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Post by racket on Dec 12, 2014 20:18:44 GMT -5
Hi Mitch The wheel I used was a Cummins jetandturbineowners.proboards.com/attachment/download/49 , the shaft is 3/4" if I remember correctly , I used a 9R-12 bearing near the turbine wheel whilst a 6303 near the sprocket , why I used and Imperial size for one end and a Metric for the other , I have no idea :-( Cheers John
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nersut
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Posts: 223
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Post by nersut on Dec 12, 2014 23:35:19 GMT -5
Hi Mitch I have a VT-50 turbine wheel, I just did some measurements for you. Diameter of the shaft at the bearings: 19.05 mm or 0.75 in (3/4") John, you remembered it correct Diameter at the compressor section: 14.41 mm or 0.5685 in Diameter at the turbine piston ring oil seals: 31.94 mm or 1.2575 in Length of the shaft between bearings, end to end: 77.14 mm or 3.0365 in (~ 3 in) This one piece aluminum alloy bearing have a O.D. of: 32.32 mm or 1.2752 in. Cheers Erik
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mitch
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Posts: 285
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Post by mitch on Dec 13, 2014 1:01:06 GMT -5
Thanks everyone for the help and responses! Looks like I'll be heading back up to the turbo shop next week to pick up that st-50!! I still can't get over how odd that bearing is, along with the plate attached to the end to prevent it from spinning. racket, Thanks for the bearing sizes. That helps a ton, looking through pages of bearings on mcmaster carr is not very fun haha. nersut, thanks for those measurements, I can start looking for bearings now! The hardest part will be creating the sleeve to hold it all together.
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mitch
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Posts: 285
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Post by mitch on Dec 15, 2014 11:32:02 GMT -5
According to jetspecs, I found a rough estimate for thrust output for the engine I will be using, is there any way to estimate shaft horsepower given thrust, and assuming free power turbine efficiency?
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Post by racket on Dec 15, 2014 14:49:06 GMT -5
Hi Mitch
Roughly up to 1 HP per pound of thrust, this will naturally vary depending on rpm used compared to its potential max rpm, and a heap of other things.
My first turbine bike developed ~110 lbs of thrust as a pure jet which then produced ~115 HP once the freepower was instaled
Cheers John
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mitch
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Joined: August 2014
Posts: 285
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Post by mitch on Dec 15, 2014 19:58:17 GMT -5
Wow!!! That is so much power for a "homemade" engine!! Then when taking gear reduction into consideration, it adds up to a large amount of power. What kind of gear reduction would you recommend? I had assumed I would use a 4:1 reduction, assuming the free power turbine will spin to a max of around 20k
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Post by racket on Dec 15, 2014 20:52:53 GMT -5
Hi Mitch
Gearing needs to consider a lot of things, potential max rpm , power output , size of vehicle , drag etc etc etc .
If you intend fitting a gearbox then your rpm could be as high as 40,000 rpm depending on the gas energy and its resultant velocities .
Ideally you need to develop the gas producer , then once you know the jet pipe energy and its mass flow , its possible to design the freepower stage and get a rough idea of horsepower and at what rpms , then and only then start to think about overall gearing for the vehicle it'll be installed in and the type of work it'll be required to do.
That original turbine bike of mine initially had not enough gearing , only ~14:1 overall between freepower shaft and back wheel , this resulted in a "low" top speed due to the freepower not being able to spin out to its full potential , the fitting of a very large rear wheel sprocket lowered gearing to ~18:1 which then allowed the full freepower rpm before the horsepower vs drag reached a balance .
Cheers John
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mitch
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Posts: 285
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Post by mitch on Dec 15, 2014 22:28:47 GMT -5
Thanks Racket, That is a lot to take into consideration. My original plan was to put it on some type of tricycle (just because mounting the entire engine assembly would be easier between the two rear wheels, vs a bicycle). Good news though, I am going to pick up the used, seized up ST-50 tomorrow for just $100! The gas producing section of the engine should be completed fairly soon, just have to finish the evaporator assembly, make a few flanges, and drill all those holes for the flametube...
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Post by racket on Dec 15, 2014 23:38:43 GMT -5
Hi Mitch
I image the trike will have reasonably big wheels , and top speed will be <60mph , so you'll be needing a fair bit of gearing .
With my 2 shaft kart , the rear wheels were ~11 inch OD - 2.91 ft circumference so ~1810 revolutions per mile , so 1810 rpm at 60 mph- 1 mile/min , with an 8.1 :1 chain redux ( 10 tooth freepower to 81 tooth on the axle ) it produced a requirement for 1810 X 8.1 = 14,660 rpm at the freepower, at 22,000 rpm ( max for the chain and sprockets used) the speed would have been ~90 mph ......LOL , never got anywhere near that on my bumpy test track, was having troubles at 70mph keeping her on the road.
Cheers John
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mitch
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Posts: 285
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Post by mitch on Dec 16, 2014 14:32:26 GMT -5
Here's the ST-50 I picked up The nut looks like its a bit rusted and corroded in place, should be fun to try to remove!
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Post by racket on Dec 16, 2014 15:12:58 GMT -5
Hi Mitch
Looks like a case for finding a container to sit the turbo in and submerge it with kero for a few days to soak through and loosen things up .
Heh heh , your old dog hasn't seen one of these before , approaching it warily ;-)
Cheers John
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