Re: my "twin bee"

lousyflyer Thu Sep 13, 2012 2:46 pm

Excellent!

**Cribbs74** Thu Sep 13, 2012 3:13 pm

Good deal, did I read that right 9K RPM?

**RknRusty** Thu Sep 13, 2012 3:17 pm

Congratulations! Great work.

ekitten2 Thu Sep 13, 2012 8:22 pm

absolutly auwsome well done

it incurrages me to finish mine

**RknRusty** Thu Sep 13, 2012 9:47 pm

Chris, was that a rich break-in run or were you leaning it out? When it was running, did it look like both cylinders were getting equal fuel? How is the fuel air mixture getting past the rear crankshaft web and into the front of the crankcase to feed the second cylinder? I keep looking at the pictures, I'm sure it's obvious.

EDIT: DUH! Through the hole in the rear web. my "twin bee" - Page 2 Slaphead

chris74100 Thu Sep 13, 2012 11:43 pm

cribbs74 wrote:Good deal, did I read that right 9K RPM?

Yes , 9 KRPM, but it is a bit weak, I thought that he would turn more quickly

Surfer_kris Fri Sep 14, 2012 1:54 am

Very nice work you've done, and very quickly too. cheers

What props size do you have in the video?
(an 8x6 at 9000rpm would certainly be excellent)

chris74100 Fri Sep 14, 2012 1:55 am

No, the prop is a 7x4

John Goddard Fri Sep 14, 2012 3:21 am

Excellent Chris very well done.
Try and get yourself a Cox 7x3.5
I know it's not much difference but it will
Really wake the engine up when you start
To lean it down.
Very Happy

chris74100 Sun Sep 16, 2012 9:41 am

The "twin cox" with her stand. It's finished..............

ekitten2 Sun Sep 16, 2012 9:44 am

oh thats soo frickin nice

Surfer_kris Sun Sep 16, 2012 10:40 am

A 7x3 prop might work a little better but the main thing holding it back is likely the restricted intake. Twice the engine size on the same intake as a regular cox babe bee, doesn't sound right. The cox queen bee at .074 has a much larger intake, venturi, and reed-valve compared to a .049.

navion34 Mon Sep 17, 2012 1:47 pm

Très beau travail.

Bientôt une production en série limitée ?

Fantastic job.

Available soon ?

Rémy

chris74100 Mon Sep 17, 2012 1:51 pm

Je te remercie, mais non, même pas un 2eme exemplaire de prévu, j'aime que me moteurs restent "uniques"

Surfer_kris Mon Sep 17, 2012 3:00 pm

How about a second one with a backplate and carb from a Queen Bee?
That would be unique enough in my book...

ekitten2 Mon Sep 17, 2012 6:13 pm

<< agrees that would be auwsome

Shnitzl Thu Oct 11, 2012 5:01 pm

what did you end up using for the crank pins?
.106 spring wire?

chris74100 Fri Oct 12, 2012 1:05 am

hi, the crank pin is in "42cd4" machining and laping with the rod

**RknRusty** Fri Oct 12, 2012 10:36 am

I didn't know what 42cd4 meant so I looked it up. It cross references in the USA as 4140 alloy steel.

fit90 Fri Oct 12, 2012 5:01 pm

Isn't 4140 chrome moly?

**RknRusty** Fri Oct 12, 2012 8:13 pm

fit90 wrote:Isn't 4140 chrome moly?

http://www.steelstrip.co.uk/international_equivalents2.htm
4140 is down the page in the alloy steels group under USA. 42CD4 is on the same row in the French column. It doesn't give any more explanation, but I thought chrome moly was mostly molybendum and no steel.

Shnitzl Fri Oct 12, 2012 8:30 pm

what little I know if any is correct.

chromium and molybdenum make up chro moly another word people refer to when asking for 41** steel.
which has allot of SAE ratings, more then I can tell you off hand. 4120,4130,4140,4150 and lots in between.

wonderfully used for rollcages or the barrels of rifles.

*edit, and yes I never really heard of 42cd4 so has to be european, and yes their always is a cross reference Razz

(< I dont know what that face is either haha)

thank you Chris, that will surely be a stout crank pin.
more effort then I did for mine.

fit90 Sat Oct 13, 2012 9:36 am

If I remember correctly, and this is a huge if, two of the numbers are for the alloy and the other two are for the Rockwell hardness. I couldn't say which are for what if I am even close to being right. If I get motivated I will look it up this weekend.

fit90 Sat Oct 13, 2012 12:21 pm

Maybe this will help a little. Just for basic identification, nothing specific.

roddie Tue Oct 22, 2013 1:23 pm

chris74100 wrote:This day, first starting for my twin cox.

Hi Chris, This is fascinating! Have you started building a 2nd one? (RE: your recent "Value..." thread) I am curious to know if you increased the "bore diameters" in the venturi tube, and/or fuel inlet nipple and used a larger i.d. fuel pick-up tubing inside the tank?

What have you run for fuel? Does the engine use a stock "reed"?

Really nice work Chris... I'll bet there's a lot less vibration with both pistons firing together.

Sponsored content