Correct me if i am wrong, but seeing as the max load on the conrod is a function of acceleration (+ve and -ve) combined with a comparativly small amount of load from cylinder pressure, then wouldn't high revs be putting on very high bearing loads also.

You might also be interested in this paper:

http://www.surrealmirage.com/subaru/files/SAE_boxer.pdf

It has some very interesting info that I haven't seen before, paticularly about the bearings.

Paul

 

Agree Paul, it is a combination of revs and torque. The load on the bearing to produce 500lb-ft torque is an average of 500*304.8/39.5 = 3858lbs. This is an average force over 180 degrees rotation, most of which has a smaller lever arm than the 39.5mm of a 2.5 engine. I'd estimate IRO 10,000 lbs peak loading from combustion alone. To produce decent power, you need to hold on to the torque up the rpm range, I had done the sums for piston/rod acceleration force but forget them.

Andy

 

bit confused.

paul, which bit are you referring to in that pdf?

Also, there is mention that the increased stiffness of the crank due to its large overlap between main and big end journals reduces friction more than the required increased big end diameter increases friction.

This makes sense except that I would appreciate someone being able to explain why a stiffer crank will decrease friction, and if so, friction between which components? Could there finally be an advantage to me having spent stupid money on a billet crank?

 

Glad to see you have all been having fun since I was away!

Anyway, back on topic a few comments.

The final build of my engine was carried out by Dave Wild at DTW. This was a much to mitigate the forever lengthening waiting time and to allow SMG to focus on fixing Johns engine.

For the record the configuration of my short engine is identical to JBs and it runs very quietly and has done right from the off.


Regarding comparitive RR runs, there will be a small issue here as I suspect that running my car in 4th will overspeed the rollers as I have very long gearing. It will of course run in third, however this will give some (not a great deal) of difference in results. If anything, slightly short gearing can give better results, however roller grip will be an increased issue with the torque figures.


Finally, which will give up first, my gearbox or my bearings. Not really sure - the main thing is that on road it is very unlikely I will be utilising all that torque - however on the rollers, quarter etc we will have to wait and see.

However, unlike some munters, I will be out there and I will be happy to give it a go

Rannoch

PS If ANYONE would like to discuss issues not relating to my project such as other peoples engines then please start your own thread. Thank you

 

What ? This is a private thread now is it Can't I even say that I had a run in John Banks's 2.5 car last night and it was very impressive for 1 bar boost Pulling well from 2500rpm with virtually immediate response It's going to be a very nice set up once the boost is raised a bit and the map sharpened up. I must try and get a run in it at Crail dragstrip just to keep the 1/4 mile title in Scotland a 'wee while' longer

Andy

 

Andy,

indeed - sounds worthy of its very own project thread if you ask me!

Rannoch

 

 

come on then, tell us how it drives.

 

I went out in Davids car with him tonight.. and OMG, the noise is something else..

David

 

Excellent!

Tell us more

Simon

 

yes, the porsche is lurrvley

 

 

PMSL!!

Looking forward to your report Trout


Rob.

 

LOL

for a split second I thought we may actually see a christmas/new year show down , as posted elsewhere.

 

LOL..

Simon

 

we might.. you wont

 

Ah , big fish small pool

 

<snatches wooden spoon and kicks andy>

<crunchie.. - friday feeling >

 

we might.. you wont

suppose the graphs would be a bit tricky to live up to in public

 

I sit here with my right hand firmly gripping The Mighty Swword (of dobber) in anticipation.

Please lets not go down the (too) well trodden path.

Paul

 

T-uk you may be interested in this snippet from Rannochs website, posted almost one year ago !
Just as well he didn't say which year

Andy

(that spoon's mine wallis )

 

Rannoch
Scooby Regular
Posts: 1440
From: one car to another and back again!
Registered: 21-01-1999
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posted Saturday, November 22, 2003 12:35

--------------------------------------------------------------------------------
Quick update - engine finished and off to be put back into car


so which engine will we get to read about

hands spoon back to wallis , since it's the only action in this thread

 

<leans back in chair with a smug grin>

 

<leans back in chair and

























falls asleep>

 

[Edited by Pavlo - 12/8/2003 8:32:42 PM]

 

Zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz

 

Back on to topic.

Is it installed in the car yet? Any pics?

Alan

 

may-be grown into a 2.36

paul, why the late edit? you and DW hinted that the engine was a goer , which is what the threads originator wanted

[Edited by T-uk - 12/9/2003 5:51:27 PM]

 

This is all in riddles.

What do you mean?

Alan

 

will mail you alan to keep this thread on topic for the poster.