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Post by racket on Jul 2, 2020 20:33:55 GMT -5
Hi Scott
Excellent run :-)
Top speed .......thats gunna be a hard one to guess , but maybe 70-75 mph terminal depending on how well you tucked in and the A/B performance .
The machine has been beautifully finished , you guys know what you're doing ................great pit crew support ;-)
New project will get their juices running , good stock of ear plugs required.
Cheers
John
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Post by pitciblackscotland on Jul 2, 2020 20:50:10 GMT -5
Hi Scott, well done mate  all that hard work has paid off I guess about 55 - 60 mph. Looking forward for more runs. Cheers, Mark. |
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Post by slittlewing on Jul 8, 2020 9:42:03 GMT -5
Thanks for the support and kind comments guys! I’ll be sure to post up the top speed when tested (but I think it’s pretty meagre haha)
Cheers
Scott
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Post by racket on Jul 8, 2020 17:40:50 GMT -5
Hi Scott
Top speed will be interesting , it takes ~8 hp to do 60mph on a bike , so using the formula of HP = resistance X feet/sec divided by 550 we end up with a resistance = 8 X 550/88 ft/sec , so a resistance of 50 lbs , which will need a thrust of 50 lbs to overcome, you should be producing more than that.
Cheers
John
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Post by slittlewing on Sept 23, 2020 16:09:18 GMT -5
Been a little while since posting due catching up on lots of adult life boring stuff getting in the way (DIY/House on market/Car maintenance blah blah) Anyway, I have managed to squeeze in the last few jobs on the Jetbike: -small heatshield covering 3D printed parts on swingarm that we’re melting from radiant AB heat -rear shock preload backed off to try and get a degree or more horizontal on AB output -custom front fairing 3D printed and glossed up -front mudguard lacquered and forum web stickers finally applied The fairing was my 3rd attempt and very time consuming to make, being a bit of an experiment to turn a rough 3D printed part into a lacquered body panel! Ended up perfect at about 2mm clearance to the factory fairings at full lock.             The last job is to tweak the AB fuelling, I want to try and throw some more fuel in at high P2 before doing the “top speed run”. Last time I attempted it, I tried it at idle too which resulted in being too rich and lots of smoke/bangs. But hopefully there’s more to come at higher airflow 😈😈 Cheers Scott |
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Post by slittlewing on Oct 17, 2020 12:57:11 GMT -5
A little update.. I have had a tricky few weeks with the Jetbike. Firstly I was trying to find a suitable "test site" for doing static testing ahead of a "top speed run". 3 weeks ago I went to a local farm which houses 50 microlights and an airstrip, and asked if I could do it there. The farmer said I could come and "demonstrate" the engine for him to assess if it was too loud or not. With about 3 hours of daylight available, I quickly took the bike to the farm and fired it up for the first time since summer. Ran it for a approx 2 minutes and afterburned - he said it was too loud  With the cold UK temperatures, I didn't have much oil pressure as my PWM temp-scaling was off, and the pump was almost stalling trying to push the thick 10W60 oil round with little speed or PWM. I didn't have my laptop to reprogram or tweak it, and so did the short run anyway. At the end of the run there was a strange buzzing noise which I assumed to be a problem with one of the electric pumps. Then I found another test site, but it rained all the next weekend so I put off doing the testing. Last weekend the weather was finally "OK", and there was an open event at Santa Pod (UK 1/4 mile dragstrip). They agreed I could do static tests in the car park and kindly gave me a cordoned off area. Again I had low oil pressure, I increased PWM before starting until it was on target. I was aiming to increase the AB fuelling to get maximum thrust, before it was so rich that it went out. To do this, I would have the ECU unbolted from the bike and turn a pot (which was linked to the AB fuelling gain in my code). Unfortunately having the ECU lid off meant that I ran back into EMC issues when the spark plug fired to start the bike. A couple of failed starts and one bottle of scuba was gone! So I programmed "maximum" AB fuelling (AB Fuel pressure gain of 2.7->2.8 compared to P2 Pressure) and put the ECU back in its position with lid, to try it without EMC issues. Fired it up and the AB went out at high throttle.. too rich I thought. I reverted to "known good" AB fuelling setting from the farm (Gain of 2.6), and thought I best try a run before I used all the scuba air! I ran one 1/4 mile test and had the same issues with the AB going out, despite running the same settings as the farm where all was fine! I felt some occasional nasty vibration through the bars, that I suspected was a pump problem. Then it rained heavily and the day was put to a stop We decided to go for one last static test while I had the possibility of doing it in their car park. This time, I ran the shakedown AB fuelling (Gain 2.5). Yet again the AB went out at high throttle. The nasty vibration was also present. After feeling all the components, it was evident this was from the turbo. This week I fully stripped the bike down and yep - the turbo is dead!! Wheels have touched housings on both ends, >1mm of shaft play. I was lucky it didn't explode under my balls hahaha!! The turbo had done well for a £60 ebay snotter, its seen a good amount of testing but is now a sacrifice to the gods of speed (slow speed). Metallic debris has also been through the oil pump (rotors are damaged). Annoyingly its quite a rare/odd turbo, and hard to find a direct bolt on replacement but I am working on it!! The bike is so tightly packaged around the turbo that I can't change to a different size without re-engineering everything, which I don't fancy doing for a 3rd time haha.     In terms of why it failed, I am sure its due to the short farm run with low oil pressure in ~5deg ambient. The 10W60 oil I had been using has always seemed too thick when cold, as the pump speed is very low before the oil has warmed - verging on stalling. This even caused me to blow some mosfets during the early stages of ECU testing before I had an 80A capable circuit. The high viscosity means it has very low flow for a given pressure. The low flow then means it takes longer to warm up aswell. After some further analysis, it seems 10W60 has a much more exponential "thickening" in viscosity compared to a standard grade of 10W40 or 5W30. In future, I will probably use something like 0W30 for a much less exponential change in viscosity and higher flow rate when cold!!  I will make a video from the run footage, just to document the progress of the project and will post in due course  A good bit of learning anyways, even if it is the hard way haha!! Cheers Scott |
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Post by wannabebuilderuk on Oct 17, 2020 14:35:33 GMT -5
That's a bummer on the turbo but agreed its a good thing it didn't go pop between your legs haha.
Certainly had a good run and you've learned a nice bit from it so pop it on the shelf as a reminder of what you've achieved so far and carry on building!
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Post by racket on Oct 17, 2020 19:10:07 GMT -5
Hi Scott
With that sorta impact your air/gas flow through the A/B wouldn't have been too consistent which possibly exacerbated the A/B combustion .
Bummer about it killing the turbo , but at least now real damage to the bike , coulda been worse .
Yep , you'll be needing "thinner" oil in your winter temperatures , maybe fit a tank warming pad
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Sweetenough
Veteran Member
Joined: April 2016
Posts: 121 
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Post by Sweetenough on Oct 20, 2020 6:19:32 GMT -5
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Post by slittlewing on Oct 25, 2020 12:01:34 GMT -5
Thanks for the encouragement chaps, I am trying to source a HX50 (non wastegate) with larger wheel sizes. I will probably need to lengthen the AB pipe to the outlet flange on the turbo in this case. I am also considering fixing the combustor end where it meets the turbo (its only 5mm thick and has bevelled, providing an air leak at the turbine inlet flange). I may cut this off and go for 10 or 12mm thick. The aim is to get it back together for some more fun next year.
Good idea on the tank warming pads, some googling has led to me finding 12v ones that I could power using my car (whenever taking the bike somewhere to do testing, I have no mains power)
Cheers
Scott
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Post by slittlewing on Nov 9, 2020 17:26:45 GMT -5
Well, after lots of hours on google I found what I consider the perfect replacement turbo for my Jetbike. A HX50 with largest possible wheel sizes in the "frame size", and a perfect 25% larger turb exducer than comp inducer. I found one which appeared to be a bargain in Poland, and after lots of emails and google translate... today it arrived!        I think I have lucked out, it looks like a straight swap excluding a 25mm extension required to the afterburner tube, to account for the lack of longer "wastegate" housing the old one had. With ~20% more area than my old 63mm compressor, I will probably go up on kerosene nozzle size and try and push this turbo harder than the old one. With Previous turbo appearing to be close to "choke" region, I hope this one may be able to build more pressure against my existing flame tube without overspeed. I will be changing to 0W30 and targeting 4bar oil pressure, as well as fitting a gauze pre oil pump. I intend to use the "opportunity" of engine out to fix some annoying problems - -Grind off old combustor cap and change for 10mm thick one (5mm bevelled under pressure, doesn't seal properly) -Change to 10AN oil drain pipe for turbo rather than rubber pipe and clips -Fit swaged connections on silicone boost hose Thats the plan anyway...! Cheers, Scott |
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Post by wannabebuilderuk on Nov 9, 2020 17:51:35 GMT -5
Good ebay hunting, can't wait to see the beast running again!
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Post by racket on Nov 9, 2020 18:34:54 GMT -5
Hi Scott
Thats a nice turbo, should do the job :-)
Do you have a Link to the Ebay supplier, its exactly the size that would work with a TV94 turbine wheel as the freepower ??
Cheers
John
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Post by slittlewing on Nov 10, 2020 14:19:01 GMT -5
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Post by wannabebuilderuk on Nov 10, 2020 14:41:44 GMT -5
Man things are cheap in Poland... More reliable version of China I'd say lol
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all that hard work has paid off 
