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Author:  The General [ Wed Sep 01, 2010 7:36 pm ]
Post subject:  Miniworld feature
Hey all, just got the new miniworld through the post.

Anyone on here own the Silver VTEC from QLD? Or any more pics/build diary for it?

Sorry I don't know many people on here, I've not long moved to Oz from the UK, and I'm yet to find a mini to tinker with!

I'm really interested in doing a VTEC conversion in a mini, I know a few on the forums are trying.

Lee
Author:  simon k [ Wed Sep 01, 2010 9:00 pm ]
Post subject: 
The fella with the silver VTEC isn't on here (unless he's a quiet lurker). Honda conversions aren't as popular here as they are in UK, toyota 4EFTE's are the done thing. I'm doing a Honda, but very very slow progress

welcome ;)
Author:  The General [ Thu Sep 02, 2010 7:02 am ]
Post subject: 
Hey Simon,

Are you building your own subframe for your conversion?

I think I'd like to build my own as none of the ones I saw in the UK did the job perfectly. I have seen one that does look pretty good though- a guy called Gianni Potenza has built some subframes for B16/18 in a standard roundnose.

What I'm struggling to understand is the compliance? Is it right all conversions need to be checked by an engineer??

Cheers

Lee
Author:  TheMiniMan [ Thu Sep 02, 2010 12:39 pm ]
Post subject: 
The siver V0tec roundy is probably Nathan Wilson`s from the Gold Coast, featured in "The Mini Experience" last edition
Author:  Kennomini [ Thu Sep 02, 2010 9:28 pm ]
Post subject: 
If you build or modify your subframe in any way it will need to be approved by an engineer to confirm it's safe and strong, it should equal or exceed the standard item.
Author:  simon k [ Thu Sep 02, 2010 9:54 pm ]
Post subject: 
The General wrote:
Hey Simon,

Are you building your own subframe for your conversion?

I think I'd like to build my own as none of the ones I saw in the UK did the job perfectly. I have seen one that does look pretty good though- a guy called Gianni Potenza has built some subframes for B16/18 in a standard roundnose.

What I'm struggling to understand is the compliance? Is it right all conversions need to be checked by an engineer??

Cheers

Lee


yep, must be approved by an engineer, regulations vary by state. Archangel007 is probably the most au fait with QLD regs

yep, I'm doing my own subframe - not made a lot of progress as I changed recipient shells to one that needs a lot more body work.... not enough time either. Usual story

The majority (if not all) transplant subframes in aus have been custom made. There isn't enough of a market for a company to come up with a design, and go through all of the potential legal hurdles to produce one. I believe there have been a few people bring a Honda subframe from OS, and have had problems with getting them engineered to fit within regulations.
Author:  The General [ Fri Sep 03, 2010 7:13 am ]
Post subject: 
Thanks for your replys.

With regards to engineers, how much "engineering" do they need? Would it be sufficient to draw up a 3D CAD model and FEA? (I'm a draftman by day)

Or is it a case of building it and seeing what he thinks?

Thanks for pointing me in the way of Archangel- I'm about halfway through his build post! Seems everyone has a different opinion RE engineers: what does it take to become one of these engineers? Are there comapnies doing this or one-man-shows?

Sorry for all the questions- most of my friends in Oz aren't car people!


Thanks

Lee
Author:  blue_deluxe [ Fri Sep 03, 2010 9:08 pm ]
Post subject: 
You could use FEA as a guide, but its quite easy to stuff it up and get all sorts of funny numbers come out. crap in, crap out in other words.
Ive tried it a few times for uni and mini bits but never got anywhere at all.
Id assume youd give the engineer a soft copy of the model and hed go away and analyse, but thats just my assumption ive not seen an engineer for my project.


With regards to becoming a queensland transport recognised engineer, ive heard everything from have an engineering degree and filling in the right forms and paying the right money to a mechanic with a few years experience that filled in the right forms and paid the money. Can anyone confirm anything?
Author:  Mokesta [ Fri Sep 03, 2010 10:36 pm ]
Post subject: 
I have been told there is a young guy with two honda engined minis in brisbane. One running a b16 and the other nearly complete with a b18. I have tried to get him to join here but no luck yet. I don't know him. Friend of a friend.

Becoming a Qld transport Authorised Officer takes different qualifications depending on what you want to be able to certify. Many are not qualified engineers if all they want to certify is relatively routine stuff.

Most authorised officers I've come across will just look at a frame and either decide they don't want to touch it or say looks right and sign it off. There is very little engineering involved.

One Registered Professional Engineer and Authorised Officer who I respect said that he would want to see that section moments of inertia were bigger in each direction for the items cut off and replaced and he would just use experience to assess joints. He also said he would certify a frame for a select few people and the rest can go somewhere else.

If you want to FEA it correctly, you can't use the dinky little FEA packages that come as a cheap add on to a 3D package. You'd have to do it properly. Frames are complex so the usual "cast widget" type of FEA analysis doesn't work out. Too many elements and element shape all wrong. You need to model the frame as a series of zero thickness surfaces then use plate elements in the mesh. Some high-end FEA packages can turn your solid model into surfaces by mid plate surfacing but they often have trouble joining the edges. If you draw it with zero thickness and make a SAT file you've got a chance of modelling it right.

BUT, you haven't got any load cases or fatigue analysis so now you need to model the stock frame and do a comparison analysis. The stock one works so your new one must be stronger/stiffer in all directions by the ratio of engine power you want to increase. How many load cases are you going to do???

Be very careful about copying frames you see on the net. Many have fundamental flaws, even some that have been approved. Commonly it is a gross lack of longitudinal stiffness at the front track rod mounting location. Also a reliance on the tower, a thin-walled cylinder, to rigidly support a large cantilevered load without any suitable bracing or re-inforcing.

M
Author:  amos [ Fri Sep 03, 2010 10:56 pm ]
Post subject: 
Mokesta wrote:
I have been told there is a young guy with two honda engined minis in brisbane. One running a b16 and the other nearly complete with a b18. I have tried to get him to join here but no luck yet. I don't know him. Friend of a friend.

Becoming a Qld transport Authorised Officer takes different qualifications depending on what you want to be able to certify. Many are not qualified engineers if all they want to certify is relatively routine stuff.

Most authorised officers I've come across will just look at a frame and either decide they don't want to touch it or say looks right and sign it off. There is very little engineering involved.

One Registered Professional Engineer and Authorised Officer who I respect said that he would want to see that section moments of inertia were bigger in each direction for the items cut off and replaced and he would just use experience to assess joints. He also said he would certify a frame for a select few people and the rest can go somewhere else.

If you want to FEA it correctly, you can't use the dinky little FEA packages that come as a cheap add on to a 3D package. You'd have to do it properly. Frames are complex so the usual "cast widget" type of FEA analysis doesn't work out. Too many elements and element shape all wrong. You need to model the frame as a series of zero thickness surfaces then use plate elements in the mesh. Some high-end FEA packages can turn your solid model into surfaces by mid plate surfacing but they often have trouble joining the edges. If you draw it with zero thickness and make a SAT file you've got a chance of modelling it right.

BUT, you haven't got any load cases or fatigue analysis so now you need to model the stock frame and do a comparison analysis. The stock one works so your new one must be stronger/stiffer in all directions by the ratio of engine power you want to increase. How many load cases are you going to do???


M


I'd be surprised if the stress and deflection that the new subframe would need to withstand is a function of engine power. The stresses and deflections faced by the subframe would mainly be the suspension loads being fed into the sides and the static load of the engine. Although I guess the torque supplied by the engine would be a function of the engine installed. My way of thinking is that two of the three engine mounts are taken by the towers which remain almost unaltered anyway (I'm talking a 4EFTE conversion here). The engine mount which is going to react engine torque is the rear lower one. The other two basically support the weight of the engine.

Given the right CAD and FEA package you could easily do a comparison, but i'm talking $. We use Pro-Engineer and Inventor coupled with ANSYS at work - so could easily do it but i'm not even going to that sort of level of detail. Using fundamental engineering calcs you could show stiffness, deflection and stress comparisons if you want. At the end of the day it'll be some guy (in some instances an experienced degree qualified engineer) who will say yay or nay... if he says nay he tells you why, you trundle off and fix it and take it back for round 2.

I've been told a series of stories when it comes to approving in SA. I think the company that is responsible has to be registered with TransportSA or something... I've been told that you need to be degree qualified, that you need to be degree qualified and have a Chartered professional (CPE) status and i've been told that you need to be degree qualified, CPE and some sort of assessment by TransportSA. Admittedly i've not looked into it and this is probably just heresay.

I'm certainly not going to be FEAing mine - too much like work on a project i'm meant to be enjoying! :)
Author:  simon k [ Sat Sep 04, 2010 12:06 am ]
Post subject: 
Mokesta wrote:
Be very careful about copying frames you see on the net. Many have fundamental flaws, even some that have been approved. Commonly it is a gross lack of longitudinal stiffness at the front track rod mounting location. Also a reliance on the tower, a thin-walled cylinder, to rigidly support a large cantilevered load without any suitable bracing or re-inforcing.


ditto.... and some of them have actually failed in that area after a relatively short amount of time on the road
Author:  Benyni [ Sat Sep 04, 2010 9:08 am ]
Post subject: 
TheMiniMan wrote:
The siver V0tec roundy is probably Nathan Wilson`s from the Gold Coast, featured in "The Mini Experience" last edition


Image

Image

Is this that mini in Question?

These photos are from Matt's Stand from last years Muster!
Author:  simon k [ Sat Sep 04, 2010 10:21 am ]
Post subject: 
lovely clean job
Author:  Mokesta [ Sat Sep 04, 2010 11:08 am ]
Post subject: 
amos wrote:
... Although I guess the torque supplied by the engine would be a function of the engine installed.
...


That's the load case I was talking about, especially as the conversion most likely results in substantial wheel & tyre upgrades too. We are talking about engines with 4x the torque of the original motor. Obviously braking loads and cornering loads are engine independent.


amos wrote:
... the towers which remain almost unaltered anyway (I'm talking a 4EFTE conversion here). The engine mount which is going to react engine torque is the rear lower one. The other two basically support the weight of the engine.
...


The towers in the stock frame do not have big bits of steel cantilevered off their thin sides so they are hardly un-altered with a 4efte conversion. In the stock frame the z sections the engine sits on form a continuous beam from front right to the rear with the towers and rear legs providing the torque reaction to the overhung front engine weight. The load path with the engine hung off the towers is not the same.

You can't say that one mount provides all torque reaction. You need two connections to provide a torque so the rear mount and the side mounts provide the torque reaction. If there is a vertical load on the rear mount there will be equal and opposite additional load placed on the side mounts.

One of the engineers I work with has a PhD in FEA and his assessment of the limitations in Ansys when it comes to complex, thin-walled sections is that extreme caution must be taken if buckling is to be assessed. Even modelling the complex curves, overlapping 2.5mm sheet with spot welds is not that easy. It may be easier in ProE but not so simple in Inventor.

All the above says it's possible to analyse but not simple. It also suggests that the best method is that used in 1958, do the simplified calcs, build it and test it to destruction, then fix the weak bits. Just pray that any failures are spotted before there is any catastrophic failure on the road.

M
Author:  The General [ Mon Sep 06, 2010 7:37 am ]
Post subject: 
Thanks for the replies guys!

Mokesta- I did some Ansys work wile at Uni (had to improve the overall stiffness while trying to reduce the number of elements and thus lower the weight of a spaceframe car). It has been a while since i have used it, so I'll have to refresh my memory of it and give it a go. This was modelled as zero thickness and a relatively small mesh (the smallest our comps could handle for a <12hour analysis). I agree the would be no way of modelling the original and finding out some figures to 'improve' the frame for an engine conversion, but the must be a way of getting some figures for the engineers to consider (rather than building a frame and getting an answer "well it looks like its going to be good enough")

While I understand what has been said regarding the cantilever loads, and torque reactions, there is so much that can be modelled. There are a finite number of hard points for the front of the car front tie bar, lower front arm, upper arm mounts, engine mounts etc. Only some of these would change in a engine conversion, and although the hard points for the suspension would be under much larger acceleration and deceleration loads, these points would simply need to be reinforced from their original.

As for the loads and reaction torque the frame is going to be under, can it not be assumed (yes we're into a world of trouble already) that it will be a function of the new engines' weight and torque (reaction torque will be a function of the actual torque supplies to the wheels, with the axis of rotation around the drive shafts) and these forces used on the engine mounts have a moment force plus the dead load of the engine?

I am no expert, and I am trying to learn, so sorry if I have stepped on some toes!

:oops:
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