Holset build

[lofi]

Hello!

Having read a load of forum threads and asked a bunch of stupid questions, I'm finally starting my build.

It's based on a Holset H3B I got hold of for pennies on ebay. A few more ebay purchases to construct an oil pump and a bit of CAD work in OnShape to design the combustor for laser cutting, and I'm just about ready to start.

The oil pump is a Frankenstein construction of random parts: 

Hammond die cast box. Serves as both the tank and a mount for the pump and motor.
Scooter motor.
10-50V 40A PWM controller.
After-market oil pump from an air cooled Beetle. I liked the Subaru pumps that John uses with the integral filter housing and relief valve, but I just couldn't find one. This is similarly self contained and only needed a minor mod to the outlet. I could have used a commercial pump, but they're expensive for something that covers the pressure, temp and duty cycle needed.
8mm UJ.
8mm flange block bearings.
Bulkhead fittings.
Various odds and ends I found around the workshop.

I also found this nice T6 flange with gasket. It wants some finish machining, but it was cheap

Anyway, to the pictures! Because we all love pictures...

The oil pump



Annealing a bolt to machine into the new pump outlet



Finished pump outlet:



Tank under construction:













I still need to mount the motor and cut holes for the feed and return, but have to wait for the bulkhead fitting to arrive before I do that. I'll need to make a plate for the return to flow over to de-bubble, but I'll probably get that laser cut along with the combustor.

[lofi]

And on to the combustion chamber... You'll see that I'm and interesting mix of old and new school. I'm just as happy with marking fluid and a sharp scriber as I am with a parametric CAD tool. A few hours with Jetspecs and OnShape yielded this:




The flame tube template for actual cutting, along with a few other parts like the transition from flame tube to turbo inlet has been designed flat, as OnShape doesn't have a sheet metal function to unwrap solid parts to a flat pattern yet. Propane injector, spark plug holes and a few other bits like that I'll do on the bench. I've also drawn up parts for the outlet flange and a diffuser exhaust in case it's needed.

A few more ebay purchases:

Mandrel bent elbow.
Inlet bellmouth.

The inlet on the turbo is 80mm, and the trumpet 76. However, the drawing shows it tapering from the base, so looks like I'll be able to chop it down axially, which will bring it to a nicer length too.. All starting to come together Hoping to do a flow/pressure test with the oil pump fairly soon to see where we're at!

Cheers

Ian

[racket]

Hi Iamn

Proceeding nicely ;-)

Cheers
John

[lofi]

Cheers John

Drawings have been sent off to LaserMaster for a final quote to be agreed for the cutting. It's actually surprisingly cost effective, so I'll save myself a load of marking out, cutting, drilling and fettling loads of stainless and get on with other jobs while I wait for some neatly cut bits to arrive in the post. Better get practicing with that TIG, I guess...

[Deleted]

Hi Ian

Nice work.... Iam uk based, happy to help

i think there mite be a few diy gasturbine at shakespear drag strip in March

All The Best
Andy

[lofi]

Thanks Andy I've been following your your bike thread! I'll keep an eye out fur events and Shakespeare, that's not too far for a day trip to see some interesting kit and have a natter.

[Chuks]

hi Ian,

nice work, I love the tool you used for a making those big holes.

what is called? did you make it?

[lofi]

Hi Skynet, it's called a tank cutter. I didn't make this one, I just adapted an HSS lathe tool to fit as it was missing the cutting bit. It wouldn't be hard to make, but you should find one fairly easily

[lofi]

Well, today has been a good day...

I got my quote back from LaserMaster for cutting combustor parts to my drawings... Everything in 316 stainless - flame tube, outer can, transition funnel, caps, flanges, joining strips, output flange and a diffuser exhaust all comes to £145 including VAT and delivery. The flanges, caps and a few odds and ends are in 2.5mm gauge too.

Take my money!

I'll have to get some bits rolled as I don't have a slip roller and I want it done neatly, but that'll be a "bung the friendly engineering shop down the road a tenner" job.

The elbow from the turbo outlet will need some fettling to make it into a nice diffuser shape as it meets the combustor, but I've modeled this, have a lovely 3" stainless mandrel bent elbow ready for the job, and have a cunning plan....

The oil pump is progressing, but I need to get the gearing right. Direct drive, it makes good pressure - 80psi - but it's turning very slowly and would benefit from some reduction gearing. I've guesstimated 3:1 will hit the sweet spot, so a hefty toothed belt and wheels are on their way from China. Luckily I anticipated this, and drilled the case lid to take a flanged bearing with an oil seal to support the 8mm drive to the pump without the motor. A bracket can then be made to hang the motor off the side of the case and allow the belt to be tensioned.
Was worth a go direct drive, as it would have saved a bit of work and complexity, and at least it gave me an easy baseline.

Pictures to follow when I'm in front of the PC next!

Cheers

Ian

[lofi]

Well, my laser cut 316l arrived, and it's beautiful:




LaserMaster.co.uk made a lovely job of it! Now to get a few bits rolled so I can start stitching it together. I rolled the cone by hand, as I wanted to see if my cone calcs were correct

The great thing is, if I need to change the FT layout for any reason, or want to experiment, I can design something up, order it, and slip the new one into place. Quite exciting!

Cheers

Ian

[Johansson]

Sheet metal parts are looking great, £145 for getting those parts cut in stainless and delivered to your doorstep is a very good price!

[lofi]

Thanks Anders! I'm not sure I could have obtained material in those varying thicknesses for much less anyway. With the amount of work it's saved, I'm very happy!

I made some more inquiries and found that they're quite happy to cut Inconel 713/718 provided I supply the stock (small quantity, so can't order in), which makes producing my own axial freepower turbine when I get to that stage quite tempting... A quote for a mild steel frame for my 3D printer is on the way too. It's like engineering Christmas over here

Cheers

Ian

[jetjeff]

Hi Ian,

Nice work on the laser cutting idea. I'll have to consider that on my builds.

Regards

Jeff

[racket]

Very nice , and at a good price

[lofi]

Thanks gentlemen. Worth considering for the hobbyist, I think. You'd be able to knock out two lovely engines a month if ready cut banks arrived on your door, Jeff! If I can be be of assistance with cad work, please feel free to give me a shout.
I even found a local firm that will cast alloy if you take a set of patterns... Old school meets new. What a time we live in!

Can, flame tube and diffuser exhaust are being rolled today.

Cheers

Ian