Jab 2200 assembly.

[geoffreywh]

Rebuilding a 2200 I find the big end clearances to high, Crank measures 45mm, big end eye 8-9 hundreths more. The b/e bearing crush is up around 17 hundreths. This is far too much. For both.

 

The manual says ( as far as I can understand.) That removing material from the ends of the b/e shell will reduce the b/e shell crush (obviously) and as a side effect reduce b/e clearance. (not so obviously) . Does anybody KNOW if this is the way to reduce b/e clearance to the factory spec of 4-6 hundreths. Normally I would have given the rods to the machinist and he would resize the eyes for me. But Jabiru, being Jabiru, may be completely different. G

 

 

[Oscar]

What shells are you using? I was recommended King CR4445AM They certainly fitted perfectly straight out of the box, for a shaft and rods that measured factory specs.

 

 

[geoffreywh]

what ever the factory supplied! Did you check the clearance?

 

 

[Oscar]

Measured using CAMit's gear, in their measurement room, by their chief measuring guy ( Ted) - much safer than me doing it - and to their factory-assembly specs. ( rods left for many hours to settle to their ambient temp. for measurement etc. ). I'll happily admit, I didn't even ask him for the measurements; if you know Ted, and he says it's right, then it's right. A man of few words, and not even Ian Bent questions his decisions... if Ted rejects parts straight off the machines, they don't go back for 'fettling', they are scrapped. Then, the reason why they were out-of spec. is investigated and corrected.

 

We were mixing'n'matching parts from several engines, to build ours on a very tight budget (thanks to Ian Bent's huge generosity in even allowing us to do that using all of his facilities, and under the watchful eyes of his guys teaching us and checking us out at every step of the way, so Ted wasn't taking anything for granted in his measuring!). We were using CAMit's certificated tools and purpose-built sub-assembly workbenches with all of their special tools and with continual reference to their 'workshop' assembly instructions, which are in some places at least, a bit more detailed and informative than the Jab. Re-build manual.

 

My co-owner and I had both built, albeit some time ago, reasonably successful 'hot-rodded' engines for club racing and rallye work; we know how to use most tools acceptably well. Following what we learned at CAMit, I can say with total confidence that I would NEVER attempt to re-build a Jab. engine at home (well, not to fly behind, anyway!) , even though I have a reasonably decent workshop. That doesn't mean I don't think other people can do a fine job, it just means that I recognise that I don't have the 'edge' of skills to do the job at the quality I saw being done at CAMit. Some of the work is time-critical - such as the case-closing assembly sequence, if using the standard Jabiru Loctite sealant on the cases - and without a lot more experience than we had, we simply could not have done it. (Watching the engine-assembly guys, who have done many hundreds of engines, was like watching an Olympic gymnast's routine - awesome). CAMit don't use that sealant on CAE engines...

 

 

[geoffreywh]

So, following the factory manual proves correct. you can reduce the "bearing crush" to reduce the bigend clearance. I set the big end clearance at 0.04-0.05mm and got a bearing "crush" of 0.05 -0.08mm which is exactly what I wanted. It did take an hour for each big-end. But that's ok.

 

Concerning Jabiru engine assembly.

 

It's not rocket science, it's not laboratory work, you don't have to normalise rod temps or anything extreme. Just Be Clean, Be Careful, Measure Carefully. Wear gloves ( graphite is a bastard to get off ) . Follow the manual and it will be fine.

 

 

[facthunter]

Don't you mean reduce the big end clearance and that reduces the crush? Nev

 

 

[geoffreywh]

no. i reduced the crush to get smaller b/e clearance as b/e is more important according to the manual

 

 

[Oscar]

So, following the factory manual proves correct. you can reduce the "bearing crush" to reduce the bigend clearance. I set the big end clearance at 0.04-0.05mm and got a bearing "crush" of 0.05 -0.08mm which is exactly what I wanted. It did take an hour for each big-end. But that's ok.Concerning Jabiru engine assembly.

 

It's not rocket science, it's not laboratory work, you don't have to normalise rod temps or anything extreme. Just Be Clean, Be Careful, Measure Carefully. Wear gloves ( graphite is a bastard to get off ) . Follow the manual and it will be fine.

I agree that it's not lab. work, but I can vouch from personal experience just how close some tolerances can be. We were installing the CAE through-bolts and studs - which are quite different to the Jab. ones, as they incorporate the case positioning dimensions instead of using dowels. We had drilled the cases (by hand, under Ian Bent's instruction and using his special drill, in a very good drill-press). We did - as one does - a trial install.. (The CAE bolts and studs have to be installed in the cases before the cases are joined). Everything went into the first case perfectly - gentle tap-fit with a nylon mallet - very reassuring.

 

Then, we went to fit the second case. No way would it slide onto the case positioning area of the bolts and studs. It was still slightly warm from the drilling... 30 minutes later, when it had cooled to ambient, it happily slid home with the same gentle taps with the nylon mallet.

 

And that's for through-bolts and studs straight off the CAMit machines. No lapping or polishing.

 

 

[facthunter]

We seem at cross purposes Geoffrey. You need crush to stop the bearings moving and fretting in the crankcase or conrod. (and make sure the heat transfers out). The variation of the clearance (and crush) is rather large in those specifications. Nev

 

 

[ozbear]

If your tunnel sizes are in tolerance and your crank size is within tolerance then your bearing clearance and nip or crush should be correct if not it's a problem with the bearings themselves so try a different brand my advise is don't go filing anything off the ends of your bearings also get hold of some plastiguage and check your clearances with it

 

 

[geoffreywh]

If you read the manual it says that the bearing clearance is the MAIN goal. It is important that there is some bearing crush, the amount is of secondary importance........They describe how to "lap" the shell ends on wet and dry 600 to achieve tighter clearance at the expense of bearing crush. ...As I started with (journal #1 exactly 45mm ) 0.17 bearing crush and 0.10-11 big/end clearance. I deduce the big end eye is a bit big. Following the manual I now have correct b/e clearance and just over the minimum crush. All were similar. On dismantling the engine originally the b/e shells looked terrible. Waaay to much clearance. I'm ok with it now...............Just following orders...........BTW I don't use plastigage. I use mike and bore gauge..............Another interesting item came up today. Checking the ring gaps (new barrels and pistons) I came up with 0.43mm. on the first one. I Check the manual, it says " New piston rings usually measure 0.50 - 0.60mm !" with a maximum of 1.2mm. WTF does that mean? What are they supposed to be? My usual rule for a/c engines would be 4 thou per inch of bore. So my .45 is spot on.....I just worry about things like that........Especially as the manual also says . New cylinders MUST BE 107.5 mm long. My news ones are sweetly marked and measure 107mm. I can really do without this S***

 

 

[ozbear]

If you read the manual it says that the bearing clearance is the MAIN goal. It is important that there is some bearing crush, the amount is of secondary importance........They describe how to "lap" the shell ends on wet and dry 600 to achieve tighter clearance at the expense of bearing crush. ...As I started with (journal #1 exactly 45mm ) 0.17 bearing crush and 0.10-11 big/end clearance. I deduce the big end eye is a bit big. Following the manual I now have correct b/e clearance and just over the minimum crush. All were similar. On dismantling the engine originally the b/e shells looked terrible. Waaay to much clearance. I'm ok with it now...............Just following orders...........BTW I don't use plastigage. I use mike and bore gauge..............Another interesting item came up today. Checking the ring gaps (new barrels and pistons) I came up with 0.43mm. on the first one. I Check the manual, it says " New piston rings usually measure 0.50 - 0.60mm !" with a maximum of 1.2mm. WTF does that mean? What are they supposed to be? My usual rule for a/c engines would be 4 thou per inch of bore. So my .45 is spot on.....I just worry about things like that........Especially as the manual also says . New cylinders MUST BE 107.5 mm long. My news ones are sweetly marked and measure 107mm. I can really do without this S***

Hi Geoff

I personally would have resized the Conrod if it was over tolerance by reducing crush ie wet and drying the bearing ends you have actually made it worse and may end up spinning a bearing or reducing heat transfer and increase fretting.

 

With air cooled engines ring end gap I've found .005" min per 1" bore size works which is checked in the unworn section of course.

 

Plastiguage is a good idea as a backup as it tells you what the clearance actually is and is not reliant on feel and mathematics

 

Just my opinion from personal experience others might disagree.

 

 

[bexrbetter]

It did take an hour for each big-end. But that's ok.

You used a brand new set of big end bolts on the final assembly Shirley?

 

I have this horrible image of you torquing the big ends up multiple times while checking then using those same bolts in the engine ...

 

 

[geoffreywh]

please don't call me Shirley.

 

 

[facthunter]

I've done plenty of crush checking and you don't have to full torque them. You go to about 1/2 and then release one side and check it with a feeler gauge. New bolts are a good idea generally, though, depending on the engine. Some are fairly critical. Nev

 

 

[Oscar]

Full tension is only required to achieve the pretension for dynamic load condition.

 

 

[bexrbetter]

Full tension is only required to achieve the pretension for dynamic load condition.

You sound a bit tense there.

 

 

[facthunter]

Preload of any kind is designed to allow the design forces plus a margin, to be applied without the thing losing structural dimensional integrity. Nev