Pre-1980 VW Beetle Gas Turbine - Episode IV - A New Hope

[sebastiaan]

Cool stuff. Do you need an electronic fuel flow meter? Or could you get away with rigging up a large diameter piece of clear plastic (HDPE?) pipe to use as a large Burette and time how long it takes to (partly) empty? Bonus points for using a phone camera on a stand to take video of the burette and extract the times from there afterwards.

KISS.

[Frankenhealey]

Feb 7, 2023 14:09:27 GMT sebastiaan said:

Cool stuff. Do you need an electronic fuel flow meter? Or could you get away with rigging up a large diameter piece of clear plastic (HDPE?) pipe to use as a large Burette and time how long it takes to (partly) empty? Bonus points for using a phone camera on a stand to take video of the burette and extract the times from there afterwards.

KISS.

Electronic only please. Will be relying on fuel flow to dial in rpm for idling/noise testing etc.

[kevins]

Could you use a couple of the smaller ones in parallel and add the readings, opening the second one at 3/4 load or something?

[Frankenhealey]

For the next test session we're going to be concentrating on rpm measurement and noise reduction.

RPMs

Leaving the idea of measuring fuel flow we're going to just use the fuel tank valve fully open to measure max compressor turbine rpm (60k rpm nominal)and then try to find a reasonably stable 'tickover' speed by reducing fuel flow. Won't be far short of 20k if we're lucky. At the free turbine end the volute puts out 88 lbs/min of air at 43psi. According to 'classic horsepower required to compress air' calculations that little lot takes a theoretical 88hp with an additional 10-20% due to frictional losses. This way we will see the actual rpm at the output shaft under load and that will allow us to tune our reduction box ratio.

At the volute end we can use my Facebook Marketplace £10 mechanical tacho which goes up to 50k rpm.





At the compressor end we take off the oil pump end plate



where we have a hollow shaft that I can make up a temporary plug for with a white mark on the circumference for my cheapo handheld optical tacho



Moving on

Noise

Dragging some pics from the Restricted files we can see that turbine was fully enclosed. The covers were titanium and so all have disappeared down the scrapyard.





Now we get to the 'Please don't judge me' section. We needed some trial, temporary and mostly cheap sound reduction panels and the bodge is strong in me. If we get a worthwhile noise reduction then we can invest in metal panels with high temp insulation.

First up, need to move the Lucas high power ignition exciter.





Side panels out of some old 10mm ply as they won't see much heat





Got the ignition cable touching an oil return. Chance of it abrading to a dangerous point nearly zero but why risk it.



Moved.



Cut the other ply side panel and then scratched my head over what to use for the hot top panel. Bingo (don't judge me) I found a bit of plasterboard. It will smell but won't burn.



Cut a bit of stainless sheet to go over the exhaust to be able to balance the diffuser on top



Drat, diffuser bore is just too small so Colin the Sheetmetal King is knocking up a short length of 330mm diameter ducting and I turned a bit of strip into a band clamp.



Next up, obviously the testing, but also pull the spare turbine out of its transport frame to weigh the frame and see how we can reduce the weight that I reckon is 40 kilos. My original idea of building a frame out of aluminium extrusions may not be suitable.

[flyingphil]

Steady progress is good to see!

[Frankenhealey]

It's been a month and it's not stopped raining long enough for the field to be firm enough to do the next noise and rpm testing. The rolling 4WD chassis will turn up when it turns up so all I've got to be carrying on with is some fiddle faddle and lightweight frame work.

The noise and rpm measurement is important to future developments because after delving into even more very dry documents there are tantalising hints that the project may become simpler than I could even dream. The two bits of information are

(1) that at free turbine stall the residual torque may be only 4 ft lbs which means no N₂ brake is needed. This level of parasitic torque might make the car creep but could be easily controlled with the car brakes.

(2) that under load the free turbine can be turning at only 22,000 rpm and not the rated 46,000 rpm. That means we could only need a single stage reduction and we have a bit of a cunning plan if that is so.

Otherwise Colin the Sheetmetal King got me the 330mm collar and by 'eck can he size something accurately.





It fits



Now to do something about the horrible rectagonal sheet and utilising an old woodworking trick to get a larger concentric circle marked





Then a combination of tinsnips and RSI got me this and the sense of achievement when the two ends met to millimetre precision just like the channel tunnel



I'll make some hold-down tags so the exhaust doesn't blow the diffuser off and now to remove the the spare turbine from the humongous transport frame. I was supposed to have help with the 160lbs of reasonably delicate turbine.

First off the rigid mounts



Oopoh look the overspeed sensor output for the free turbine. I have some plans for this.



Can't use the lifting eye because it's well shrouded by the Nimrod inlet, So it's going to be wrestling a lump of metal.



Much cursing and skinned knuckles later it's on the high tech wooden pallet



And there's the transport frame ready for weighing and downsizing



Fingers crossed for a week of fine weather

[ivanhoew]

love this .

[Frankenhealey]

Apr 17, 2023 17:09:38 GMT ivanhoew said:

love this .

High praise from a builder like you Sir.

[ivanhoew]

Apr 17, 2023 19:56:02 GMT Frankenhealey said:

Apr 17, 2023 17:09:38 GMT ivanhoew said:

love this .

High praise from a builder like you Sir.

Steady on Frank. 😉.

Funnily enough this has reminded me of 2001 and being involved in mounting an artouche in the back of a fiat 500 , we converted it to thrust not shaft drive. Span it over a few times but then It was sold uncompleted. I have a pic if you’d like to see it. I didn’t want to pollute your pristine thread with it uninvited. That’s just not done. 🤓

[Frankenhealey]

Apr 17, 2023 20:19:46 GMT ivanhoew said:

Apr 17, 2023 19:56:02 GMT Frankenhealey said:

High praise from a builder like you Sir.

Steady on Frank. 😉.

Funnily enough this has reminded me of 2001 and being involved in mounting an artouche in the back of a fiat 500 , we converted it to thrust not shaft drive. Span it over a few times but then It was sold uncompleted. I have a pic if you’d like to see it. I didn’t want to pollute your pristine thread with it uninvited. That’s just not done. 🤓

Picture(s) please

[Frankenhealey]

Meanwhile how did the testing go?

It didn't because (a) it never stopped raining and (b) we had a heads-up from both the PoPo and the Coastguard that the scum-sucking, bottom-feeding pond life (SSBFPL) that are rave organisers were casing sites in the south west for another illegal bank holiday 'event'. A few years back the SSBFPLs rocked up on the Easter weekend and took over a big field on a local farm. The police were 'under-resourced' due to the holiday and therefore could only monitor the situation and 'keep the peace'. That meant they stopped the locals going in and ending the invasion toute suite with a couple of slurry spreaders. Anyhoo the farm tenants were left with a £30k land remediation bill (think rubbish, bags of excrement, rotting food, fire damage, wrecked hedges, broken gates etc.) and decided to give up the tenancy and go bankrupt so losing their home and the years of work they put in. As Clarkson found out farming can be so marginal these days and just one big unexpected bill can push you over the edge.

Big field was the driest so we were going to test there but with the news a bit of gate blocking was in order.



Luckily when they blew through all suitable fields were blocked so they gradually moved west and it all petered out around Bridport with the police proactively blocking roads and doing their job for once. The weather helped and I hope the organisers lost shedloads of money.

Still waiting for the field to dry and for 2CVChamp to get back from running the Safety Car at the Goodwood Member's Meeting to get on with my chassis.

[homersimpson]

Apr 17, 2023 22:06:45 GMT Frankenhealey said:

 The police were 'under-resourced' due to the holiday and therefore could only monitor the situation and 'keep the peace'. That meant they stopped the locals going in and ending the invasion toute suite with a couple of slurry spreaders. Anyhoo the farm tenants were left with a £30k land remediation bill

Sadly this is a familiar tale where the low life scum in society can basically do what they like and the police don't want to stop them, its much easier for them to deal with the decent people in society and control them to temper the situtation.  Ultimately they don't care who is right and who is wrong, they just want everyone to shutup so they can go back to eating donughts and drinking coffee.

[ivanhoew]

Apr 17, 2023 20:40:06 GMT Frankenhealey said:

Picture(s) please

well pox ! it transpires the hard disc with pics on is buried somewhere in the box hell that still exists after moving here .

may be some delay !


sorry ,

regards
robert

[jimi]

Feb 22, 2023 22:15:21 GMT Frankenhealey said:

We used to have one of those on the last rig I worked on, used it a few times ( but never at your kind of rpm) always seemed accurate and very stable.

[Frankenhealey]

Good weather yesterday and after an early pitch inspection we reckoned we'd not get stuck in Big Field up at Farkham Hall so loaded up the trailer we everything we thought we'd need.



Got setup but several battery powered instruments were playing up so SWMBO and Pitstop rocked up with new batteries and more importantly bacon sammiches as no great endeavour can proceed without those.







So what did we learn after 8 starts?

We've still got a fuelling problem and gravity feed is not going to cut it. Changes made had no effect. The tank is too small for the fuel consumption, we lose head too fast at a gallon every four minutes. We had incomplete starts, surge and all the woes you don't want with a turbine. Purging the system too many times after a failed start knocks out the batteries so the next spool-up ramps up slower, that increases the likelihood of a poor start.

The temporary sound panels did not help one iota as I reckon that at the one good start we had, the compressor turbine ran at 58-60k rpm. We know this because the Smiths mechanical tacho showed 5.8-6k at the oil pump which has a 10:1 reduction off the accessories gearbox. We saw levels of 118 DbA so the previous session was probably down on rpm to only produce 111 DbA. If we can get it to tickover at 30k the we could be below my target 105DbA.

We couldn’t measure the volute rpm on the Chinese tacho as the probe end threw off into the long grass. Next time it’s optical sensing or nothing. The Smiths tacho performed faultlessly but the rubber end of the probe got worn down badly.



So, all in all, a bit of a curate’s egg. We had to stop as the batteries were running down and to measure the oil pump rpm we had to take the pump end plate off and the oil loss was getting serious.



Next step is to source a fuel tank and pump to hopefully fit in the wheel well of a 2CV. Dims are 62cm diameter x 15cm deep so if anyone knows of a similar size from a scrapper then please advise.

[v8ian]

Something in my mind, about spooling up to get the speed needed,...... Nick Mann (he of Morris Minor fame) has a 4wd Mallock style car with a BDG? which used a constant speed turbo, powered by a helicopter starter motor. which was spun up with a big CO2 cylinder so it could be started.

[ivanhoew]

if stuck for a cheap tank , and not worried about weight FH , how about a lpg toroidal tank .just pop in the fittings you want , and a filler neck ? very cheaply available , and ,sometimes, free .

fill it with water first before welding .(which I'm sure you know )


regards
robert

[Frankenhealey]

May 8, 2023 18:14:36 GMT v8ian said:

Something in my mind, about spooling up to get the speed needed,...... Nick Mann (he of Morris Minor fame) has a 4wd Mallock style car with a BDG? which used a constant speed turbo, powered by a helicopter starter motor. which was spun up with a big CO2 cylinder so it could be started.

It's my fault for recycling old batteries. Plan is to have a paddock start cart along with two of these in series giving the required 24V for onboard starting. It should be 28V but who's counting?

[PhilA]

Still brings alternative options to mind.

Your going to have to run a reduction gearbox anyway, but the idea of hydrostatic hydraulic motors being driven by a pump off the turbine amuses me.

The kind of deal you get on beanstalk pickers. Run at max efficiency on the turbine all the time. No pfaff of getting it to spool up smoothly to drive.

Heck, you could install the hydraulic motor on the original gearbox...

[generallee]

Me and Mrs Generallee went to look at some tractors in a field the other weekend, I thought of this thread.



















I didn't see how they started the turbine they used to start the turbines