This discussion is becoming a bit to general with regards to bringing in other engine manufacturers and hypothetical designs. Brian spent a lot of time and effort, sectioning and measuring the VW crank to find out for himself if what he had been told was true in this case. The results showed that the counterweight are the same weight as it's opposing journal and the centre of mass for both is the same too. This shows that in this application there is no extra weight on the counterweight to balance a certain percentage of the con-rod which is what he set out to do. What do you determine as high torque and long stroke? Duratec 2.0 engines are oversquare with 87.5 bore and 83 stroke, the 1.8 K series engines are undersquare with 80 bore and 89 stroke. This leaves the VW 1.8 in the middle of these two and the 2.0 with a longer stroke still of 92.8.
and in more detail previously: The secondary forces you mention are at twice the frequency of the crankshaft, so you need balancer shafts running at twice engine speed to balance them, you cannot do it with counterweights. Most 4 cylinder inline engines are designed to be balanced up to the secondary forces, which is why they aren't as smooth as engines with 6+ cylinders. For larger engines (2.3l is often quoted as the limit) and engines that need to be smoother, balancer shafts at 2x engine speeds can be used.
Without being annoying> The last mail I got for the guy in china> ''When it comes to lightening factory counterweights, stress on the crank probably won't be as big of an issue as bearing loads will be. As a general rule, in 5 main bearing 4 cylinders, you can reduce counterweight mass if it the same as opposing journal mass but at the cost of your pin and main bearings. Best Regards'' I also have arranged a visit to his factory when Im over in the coming months which Im pretty Impressed with, he assured me Id be given the full tour and that I could take pictures of the various lines. He knows my bro over there who is also involved in engineering(plastics) so thats pretty cool, Im going to bombard him with questions LOL. Like I said guys, I dont know, hence cutting up the crank, but, after looking at what I have here, and going on the above email, I dont think Ill be knifing my crank.
Bump for new pic. Found this whilst checking out some cranks on the bay. From a Nissan YD-22 crank crankshaft X-trail primera 2.2d
Just when I thought I had found a oem 06X type crank with no internal trigger wheel I noticed it was missing counterweights like the Nissan one above. [:^(] It must be lighter than the fully counterweighted crank though. It is a diesel one, but I wonder if it will it handle a serious rev? Apparently from PD115 engine.
So are those 2 cranks above 'out of balance' because they are missing 4 counterweights? Does the weight of compression add to the mass of the big end whilst it's on it's down stroke? A crank will 'balance out' with or without counterweights, but knife-edging does put extra strain on the crank. It's hard to get your head around the math, as you can have equal weights either side of the crank working directly against each other and in theory balance each other out but it's not the best nor the worst mod out there. From experience, and thats proven experience of my own, it can work well. My own diesel cranks that I have re-worked have: 1. Lasted over 35k 2. done this mileage revving freely to 8400rpm. I have also reduced the weight on the big end side by using different rods and pistons, but not enough to 'balance' it up. Ok the downside maybe premature bearing wear, but I'm more than happy to change big ends every 20k if need be, seeing the car will take around 3-4 years to get there. Bare in mind, if you want more bhp, there are prices to pay. Lehmann recommened a rebuild after 2k on some of their top engines! Take an early VW beetle engine. It doesn't have counterweights, so the owners (usually) know not to rev them hard, as they throw cranks easily. If they want to rev higher, they started welding cranks to add counterweights. So it goes to show, you do need them, altough it's still horses for courses, if you don't rev it hard, do you need them? I must add I'm not saying go out and do it, nor am I saying that the opinions on here are right or wrong. All I'm saying is that by changing the spec of a std. engine in anyway your veering from the manufacturers spec, and maybe the completely wrong thing to do. I know VW won't warrant it if it goes bang, they've put more than enough money into R+D to get it right!
love the thread too once again Brian I m well impress by your research just a small one tho I saw different cranks : F1, nascar they had either bolted counter weight or the counter weight was drilled and tappered to fit some sort of tungsten stud in it do you think it is to allow them to thin up and profile the counter weight as best as possible and had the weight they remove with heavier material to bring the counter weight at his original weight I hope I made sense...
The question I want to know it is it possible to connect the cut parts together back together in a different order to create a slightly different engine I've always been amazed about screamer engines
HotGolf, a from what I remember, a boxer engine has far less stresses as the pistons assemblies are opposite eachother and on the same journal. I have info on the ''odd'' counter weighted crank shown above, Ill add as it comes to me. From memory, its a bit of a compromise to crank rigidity counterweighting it that way.
Can anyone remind me what the failure was on GVKs knife edged valver engine that blew to bits before he went VR? That was a carefully prepped engine that lasted no time at all from what I remember?
^Probably the most famous engine of time, for the wrong reasons...... The main failure was the single piece (instead of 3 pc) crank thrust bearing. The crank went right through it, to the point where it had enough axial play to touch/machine the block. The single piece items are reputedly weaker than the standard 3 piece items. What caused this to happen in 2 weeks has not been made public/ is still unknown, as far as i know.
This could be taken as a little dig in one direction so I'll fight my case again lol. Too late really as both engine, and reputation have been damaged. I machined the crank, and I built the block. It was totally clean, hot tanked/degreased, balanced and lubed when it left my home. Yes, I put in the single piece thrust/main bearing assembly, which at the time I hadn't had a problem with, but then found (and only after this incident) other people coming forward with the SAME problems, the crank eating through the bearing into the block. The engine was used with the old oil cooler which could have been contaminated from the previous engine that failed. The original head was also used. Make what you will of this. Yes it died, and large sheaves of metal from the bearing were found in the oil. I can categoricaly say the knife-edging was not the direct cause of this. Both sides of the crank were machined, maybe not the same amount to have an equal balance side-side, which is being stated in this topic, although lighter pistons and rods were also used and it was de-burred, cleaned, polished and balanced before fitting. I have done quite a few of these cranks, with this being the only engine one was fitted in that failed. My own first engine is still going, even with the single piece bearings in. Done well over 30k. I put my hands up to fitting a Victor Reinz 'all in one' bearing, and I also offered Gary a fresh built John Jones 2litre engine just because I felt bad. I've done work for Gary since, with no ill feeling. I can't say more than that really.
Read all this pdf, its quality stuff and a good recap for those that already know the various 'mods' that great cranks undergo/are made by http://www.ret-monitor.com/articles/pdf/crankshafts.pdf
More, detailed design considerations, > http://www.epi-eng.com/piston_engine_technology/crankshaft_design_issues.htm Great reading for those into it
