HC5A Kart build

[ausjet]

Got a few bits and pieces done over the last couple of months. Wanted to move the front brake kit to the rear axles for some more effective braking so designed some brake disk carriers and had them made at a local machine shop.







There was a dent in the afterburner support area from the first fire up early last year when I had the support rods wound up tight so finally got the time(and motivation) to panel beat it out.



Also the only 2 digital display gauges I have in the cluster- oil pressure and tot are next to impossible to see in direct sunlight. Not ideal. I’m in the process of replacing them with a more standard type.

Lastly, the seat is the first thing to scrape the ground over bumps, I’m dreading the day it wears through. Better make a skid plate for that area.

[racket]

Some serious braking power now :-)

Nice bits

[ausjet]

Hey guys, jeez it’s been a while! The HC5A jet kart is definitely still alive.
I took it out for a run yesterday. Found a nice long stretch of rarely used road about 3.7km long and an hour south of Perth. Got the kart up to 158km/h! Man that’s fast when you’re an inch off the ground. Very happy with that, 3 more kms/h and I’ll be part of the 100mhp club. Yeoww! Easily doable.
Since the last post ages ago, I have:
—Added another front brake kit so all 4 wheels are now braked. This thing pulls up exceptionally well now.
—Replaced the old seat
—Tidied up the wiring
—Replaced a faulty oil pump speed controller
—New rims and tyres
—Revised the afterburner mount after the last design. It’s now a cradle. That, along with a stiffener rod from the engine mount to the seat post has stopped engine mount flex and subsequent afterburner bouncing.

Still a few issues I need to sort out/things to do:
1. Having trouble with the engine randomly cutting out and pulsing the fuel pressure. I’ve put fuel tank foam in the pickup area at the moment to eliminate sucking air from swirl. Need to temporarily bypass the low oil pressure safety switch as it controls the fuel/afterburner relay earths. If this fixes it I’ll double check oil pressure during a run with a manual gauge and if it’s still good, not pulsing or doing anything weird, I’ll revisit the safety cutout circuit.
2. The oil cooler fan isn’t switching on once the oil gets hot. It’s a B&M trans cooler kit with integrated fan and 80on/60off temp sensor. Have previously tested the circuit with the sensor out in a cup of boiling water. Works fine. When I tested the cooler with a temp gun whilst out the other day, inlet oil would be at 86-89 degrees C, outlet 78-80 but at the bottom of the cooler where the sensor is screwed into, it sits at like 50. The bottom area of the cooler doesn’t seem to be getting much oil flow. I was thinking of relocating the sensor to tee into the cooler outlet line.
3. I need to make a better compressor intake screen. The generic aeroflow one I have at the moment doesn’t cut the mustard. It stops birds and small children being sucked in, that’s about it. Sand/small rocks being flung up from the tyres go straight in and has damaged the comp wheel leading edges. I was thinking of making a conical type one with a finer stainless mesh. Then I stumbled across pre made conical strainers that can be bought from kitchen wearhouse. Hrmmm

At the moment im running a 17gph nozzle @ 350psi for ~36psi p2. I have a 19.5gph and 20 sitting in the toolbox dieing to be fitted. Thing is, the fuel pump is capable of 1000psi so seeing 350 at full throttle tells me it’s at or near max flow and won’t net much gains from changing nozzles without going to a bigger pump.
In terms of how much I can push this thing if I did sort out a bigger pump, John, you previously mentioned this billet comp should be capable of 70000rpm. I haven’t measured shaft speed yet. Will I run into surge therefore be able to notice when rpm gets too high as an indicator or is this when I will need to setup a permanent laser tach/optical sensor viewable from the dash.







Cheers guys,
Keith

[racket]

Hi Keith

Nice day out :-)

You shouldn't run into surge with the comp/turb combo you have .

If you workout a fuel setting that produces 70,000 rpm without the A/B lit , and if your turb temps are OK once the A/B is firing at that fuel setting you should be OK , the extra backpressure should reduce your rpm .

17gph at 350 psi .............something not quite right , 350 minus 36psi P2 = 314 psi pressure drop , most nozzles are rated at 100 psi , sq root 10 , sq root 314 = 17.72, so 1.7 times 17 =28.9 gph , US gph I'm assuming , so 28.9 X 3.785 = 109 lph = 1.8 lpm = 3.1 lbs/min of fuel , thats a lot of fuel for your mass flow .

Do you have a battery problem powering the karts fuel pump for longer time frames ?? ..............I've had that sort of problem , makes the power fade away :-(

Karts looking good :-)

Cheers
John