## Are my calculations right?

Moderators: Tom, WebPilot, larry cottrill, Mike Everman

### Are my calculations right?

Well, Frist some history about me. Just so you can see that i am serious about this. I started my pulse jet career with a small valvless enging that did work but only make some big noice. After that one i manage with some help to build a valved engine that produced about 5kg of thrust, both where powered by LPG.

And now I have some big ides and the money needed A 200lb (thrust) valved Pj engine with reedvalve. This will power a "trike" that is covered with fiberglas cowling. With this vehicle I am planing on challenge (just fore fun) Erik and his teem next year on the frozen lake.
I am going to feed this beast with metanol or atleast that is what i am hoping fore. Car pertole maybe a better choise after the engine is funning fine.
This is going through two fuelinjectors from a old steam boiler ( I am restoring these for a living so i can choose diferent ones going by what you have to say)
But I need the experts word about somethings.

My numbers are
Total length:81,25"
exhaust tube length:48,75" and 7,8" wide
"Comebustionchamber" length:16,25" and 9,84" wide
Reducer length:16,25"

And here comes the first question.
My calculations shows that i need a aeria of 24squair inches and that i need to make the valveholes 34,3 squair inches, is this right? I am going by that the reedvalves are leting 70% of the air through.

Now to the second question.
Can i have a reedvalve thai is 6cm long and 2cm wide or do i need to split the so that i will have two rows (one on top of the other) that is 3x2cm.
Is it better to have short valves? I am a bit afraid that the long ones will take to long to shut resulting in "flopp".

What aluminum aloy whould be best fore the valveseet?
I am just guesing now but whould a fuel flow of 6L/min be somewhat accurate fuelconsumption
Daniel L

Posts: 21
Joined: Mon Dec 05, 2011 6:48 pm

### Re: Are my calculations right?

ok, no reply I must be right then. The exhauls tube are done and just need to be cut to the right length.
I will post pictures of my progress here (when i have some thing interesting to show
Daniel L

Posts: 21
Joined: Mon Dec 05, 2011 6:48 pm

### Re: Are my calculations right?

Oh, I have forgotten to display my progress. I will be making the valveseet in ordanary black steel for the first testing because the aluminium is taking forever to get here. Hehe, Yes i am willing to wait for it because it is free.
The exhaust tube is also done but it didn't whant to be in the picrure. It is shy

this is the inlett and comebustioncamber.
I am hoping to build some more next week

Daniel L

Posts: 21
Joined: Mon Dec 05, 2011 6:48 pm

### Re: Are my calculations right?

What the...
How can i have missed this thread for so long?
In case you don´t know. I am one of Erik´s two team members.
With next year, do you mean 2012 or 2013? I can´t find your name in the entrylist.
And FYI. In Class 38JET there are no competitors. Just partners in crime
JimN

Posts: 15
Joined: Sun Feb 13, 2011 9:00 pm
Location: Sweden

### Re: Are my calculations right?

hello
well. if this thing will get there this year is a maybe but I have a friend that have built a turbojet enging driven pocketbike. There is a thread here http://www.svensktmodellflyg.se/forum1. ... plypage=99

He just need to make it "sno/ice" ready

I am planing to have my engine done by the end of this month and the start with the trike. I don't think i will make it in time this year with fiberglas boddypanels but I am going for a running chassie.

Oh and one thing more. I was planing to get my blade steel from "spackelspadar" (sorry for the swedish) in 0,3mm but maybe you guys have some small pieces I could buy. Something like 8 pieces that are 10x10cm or 16-5x10cm
Daniel L

Posts: 21
Joined: Mon Dec 05, 2011 6:48 pm

### Re: Are my calculations right?

The third member of "Team Erik", or Svarthålet Racing wish to introduce himself. Great to see that more people have realized what motor type is the most reliable, fuel efficient and environmentally friendly.
Got so excited when my brother (Jim) emailed me about this thread so I had to post a message. Maybe this would help us gather the inspiration needed to really get going with our project.
I'll write some more later on...
LinusN

Posts: 13
Joined: Wed Mar 16, 2011 8:28 pm

### Re: Are my calculations right?

The minibike is a really cool project! I saw his name in the entrylist today.
Did you visit Speed Weekend last year? Have we met?

On your trike, are you going to use skis or wheels?

We dont have any valvematerial that big. We use ALOT of smaller ones that we bought, precut to the right dimensions, directly from Lesjöfors.
Erik is coming over this weekend to start working with our doomsday-machine. I can ask him for prices etc if you are interested.
JimN

Posts: 15
Joined: Sun Feb 13, 2011 9:00 pm
Location: Sweden

### Re: Are my calculations right?

No this will be my first year.

I will build it with wheels and the convert it to skies. In that way i can run it in the summer too. But I haven't figgered out how to brake with the skies yet. Hehe, well maybe i don't need any as the trike may not do over 100km/h.

OH that would be absolutly fantastic if you could do that. But what du you think is best ordering alot of smal pieces or two bigger ones.
Daniel L

Posts: 21
Joined: Mon Dec 05, 2011 6:48 pm

### Re: Are my calculations right?

Finaly on trake again. Today I stared on the valveplate and i finished the welding on the intake.

Daniel L

Posts: 21
Joined: Mon Dec 05, 2011 6:48 pm

### Re: Are my calculations right?

I do have all the instrumerts i need now and some parts for the ignitor system. A 30L tank was also purshed, i hope that a running time of 4-5min will be good.
Daniel L

Posts: 21
Joined: Mon Dec 05, 2011 6:48 pm

### Re: Are my calculations right?

Interesting project! Keep up the good work
kevin lee

Posts: 100
Joined: Mon Dec 05, 2011 3:54 pm

### Re: Are my calculations right?

JimN wrote:We dont have any valvematerial that big. We use ALOT of smaller ones that we bought, precut to the right dimensions, directly from Lesjöfors.
Erik is coming over this weekend to start working with our doomsday-machine. I can ask him for prices etc if you are interested.

What did he say?
Daniel L

Posts: 21
Joined: Mon Dec 05, 2011 6:48 pm

### Re: Are my calculations right?

aaah, no time to build anything untill this weekend But atleast i can show you my fuel nozzels.

By the way is the eny way to change the name of this thread?
Daniel L

Posts: 21
Joined: Mon Dec 05, 2011 6:48 pm

### Re: Are my calculations right?

Daniel L wrote:

By the way is the eny way to change the name of this thread?

What would you like it to be called?
Mike
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Mike Everman

Posts: 4775
Joined: Fri Oct 31, 2003 7:25 am
Location: santa barbara, CA

### Re: Are my calculations right?

I would like to add "now building".

this is what I manage to do today and i got my fuelpumps.

Daniel L

Posts: 21
Joined: Mon Dec 05, 2011 6:48 pm

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