Ford Crossflow bottom end question

[jcocking]

I have removed the offensive comments and negative discussions that were off-topic. Some individuals were penalized for abusive behavior. Thank you to the member who notified me of the issue.

Please get back to the conversations concerning the details on the various engine blocks. It is an exciting read, and I want to learn more.

jeff

[holywood3645]

Thanks for your help Jeff.
Back to topic on the 122 v 120 link chain option for a decked 711M, 4mm taller block. I spoke about the concern to Tony Ingram, (excellent engine builder & lotus guy BTW) Tony suggested a 1/2 link which is also called an offset link. This provides a 121 link chain… who knew!

I’m wondering if anyone here has ever used them, and could recommend a supplier.

Thanks
James

[rgh0]

If you have an decent industrial transmission supply place locally they can normally supply high quality chain in any size and specification and should know about supplying an offset link, odd number 121 links chain.

The size and pitch of the Lotus chain is a standard so nothing special there but you do need to get a top quality chain with solid roller links (not split rollers) and no removable split joining link, though the issue of having a removable split joining link is overstated I believe as many people have used them without issue.

cheers
Rohan

[rgh0]

"This link i think may be a bit more enlightening

https://askingthelot.com/what-is-the-fu ... rankshaft/"

2Cams
This link you attached is about balancing V8's which is really a whole difference problem than an inline 4. Of course in America when you talk about engine balancing you assume everyone knows your talking about V8s as is that not the only type of engine you would ever bother modifying

I also did not say that the counterweights were not important.

I just said they do not relate to primary or secondary engine balance in a conventional inline 4 cylinder engine. They do relate to control of internal bending stresses in the crank and bearing loads imposed by those stresses which is why they are different on the various types Ford 1500 and 1600 cranks

I have attached a couple of documents that go into all of this further

MSD_302_Lecture_15_-Topic__Balancing_of_Reciprocating_Forces_in_Internal_Combustion_Engines_-_20-10-2020.pdf

(261.23 KiB) Downloaded 125 times

MSD_302_Lecture_16_-_Topic__Balancing_of_Reciprocating_Forces_in_Internal_Combustion_Engines_-_26-10-2020.pdf

(54.74 KiB) Downloaded 104 times

cheers
Rohan

[2cams70]

2Cams
This link you attached is about balancing V8's which is really a whole difference problem than an inline 4. Of course in America when you talk about engine balancing you assume everyone knows your talking about V8s as is that not the only type of engine you would ever bother modifying

I also did not say that the counterweights were not important.

I just said they do not relate to primary or secondary engine balance in a conventional inline 4 cylinder engine. They do relate to control of internal bending stresses in the crank and bearing loads imposed by those stresses which is why they are different on the various types Ford 1500 and 1600 cranks

Yes - I now realise that link is relating to V8 engines.
Yes - I agree that a 4 cylinder in line engine is balanced regardless of whether it has crankshaft counterweights or not. You have two pistons going up at the same time as you have two pistons going down. The engine is balanced as a result and you don't need advanced mathematical calculus to work that out.
Yes - I agree with you that the purpose of the counterweights is to avoid internal stresses within the crankshaft itself.

Where I most decidedly do not agree with you Rohan is the assertation that the reciprocating weight (and that includes the weight of the piston and conrod) is not an important factor in the determination of what the ideal weight of the crankshaft counterweight should be - and that was my original argument several posts ago.

If the counterweight weight versus the weight of the reciprocating components is not optimally matched you will be introducing unnecessary flexing of the crankshaft along it's longitudinal plane. If severe enough this could result in a fatigue failure of the crankshaft or vibration. Whilst you may get away with it when you have a steel crankshaft (the failure part that is - you may still get vibration) you may not be so lucky if the crankshaft is cast iron.

For those of you that are still awake here are some examples of the practical application:

If you are using a 1600 crossflow crank that was originally designed to be used in combination with 1600 crossflow pistons and rods in a LTC tall block with LTC pistons and some other rod it may be worth your while paying some attention to your crankshaft counterweights if you want the best from your engine.

If you are using a L16 Datsun crank that was originally designed to be used in combination with Datsun pistons and rods in a LTC with some other kind of pistons and rods and you are having a problem with high RPM vibration it may be worth your while paying some attention to your crankshaft counterweights.

Whilst I don't know what the thoughts were going through the engineer's heads when these engines were originally conceived evidence suggests that they were thinking about the reciprocating weight when they decided what the weight of the counterweight on the crankshaft should be.

I've attempted to explain my thoughts regarding the theory in the most basic and simplified manner in the attached diagram. Note I haven't just downloaded something from the internet!

[rgh0]

I agree with you that counterweights in a 4 cylinder engine crank are all about controlling the internal crank stresses from the various reciprocating forces acting on it and the resultant flex causing bearing wear or crank failure and that it is not about engine balance and this was my original point which it has taken some time to get to, The counter weights are not about primary or secondary engine balance

Now the question is if changing cranks and piston and rod weights and pressure forces ( they also contribute) and running at different RPMs with blocks that have been modified for different bores and deck heights affecting their rigidity what is optimum solution in terms of performance, reliability and cost???

There are far to many possibilities to detail this optimum solution to all the possible modifications even if it was mathematically calculable. However there are directionally somethings better than others.

1. Use light as possible pistons and rods and make sure they are all equal in weight as accurately as possible including rod end weights
2. Use as stiff as possible and strong as possible crank
3. Dont overbore or sleeve the block or reduce the deck height and aim to maintain the maximum possible casting metal thicknesses and stiffness in the block given the build design you are attempting.
4. Dont play with the counterweights on a crank unless you have to to fit it in the block or unless you know what you doing and can analyse the internal crank stresses.
5. Listen to people who have built enough engines of the specification and combination of components you are thinking about to determine what really happens with the type of build you are planning

In the end you either build your own engines and learn over the years what works and what does not and why, as I have done over the last 40 years on twincams or you pay someone else and hope they know what they are doing.

The high vibration in a racing twincam in its nose is basically due to the secondary imbalances and block flexibility rather than crank flex or counterweights as its occurs all twin cams at 9000 rpm pretty much regardless of other detail design elements as far as I can tell.

Your $ your choice... my last comment on this thread as I think I have gone as far as i can down this rabbit hole

cheers
Rohan

[englishmaninwales]

"This link i think may be a bit more enlightening

https://askingthelot.com/what-is-the-fu ... rankshaft/"

2Cams
This link you attached is about balancing V8's which is really a whole difference problem than an inline 4. Of course in America when you talk about engine balancing you assume everyone knows your talking about V8s as is that not the only type of engine you would ever bother modifying

I also did not say that the counterweights were not important.

I just said they do not relate to primary or secondary engine balance in a conventional inline 4 cylinder engine. They do relate to control of internal bending stresses in the crank and bearing loads imposed by those stresses which is why they are different on the various types Ford 1500 and 1600 cranks

I have attached a couple of documents that go into all of this further

MSD_302_Lecture_15_-Topic__Balancing_of_Reciprocating_Forces_in_Internal_Combustion_Engines_-_20-10-2020.pdf

MSD_302_Lecture_16_-_Topic__Balancing_of_Reciprocating_Forces_in_Internal_Combustion_Engines_-_26-10-2020.pdf

cheers
Rohan

Looking at the first of Rohan’s attachments…I’m very glad I gave up Maths A level after 2 weeks and pursued a career in Medicine rather than my first choice of Engineering
(All interesting, though! Keep it coming)
Malcolm