44 replies to this topic

[ls2lxhatch]

Are those lower shock bolts/threads strong enough to take that constant beating?

 

That's the sixty four thousand dollar question Daz.

 

I would assume their custom lower control arms would be designed to take the load...

 

McDonald Bros LH-LX Tubular Lower Wishbone.jpg

 

...but personally I hate the idea of the vehicle's weight being supported by two small lower shock mount bolts each side.

 

The arms have been engineered for road use.

 

The shock is typically mounted on top of the arm so the lower shock mount bolts do not take any significant load.

 

 

The shock can be mounted through the arm if you remove the t-bar from the shock, put the bottom of the shock through the hole and then reinstall the mount t-bar in the shock. In this configuration the bolts do take the load.

 

The two bolts supplied are grade eight 3/8" UNF with a 9/16" wrench size. The proof load for a 3/8 UNF grade 8 bolt is around 10,500 lbs.

Edited by ls2lxhatch, 10 December 2015 - 08:06 PM.

[ls2lxhatch]

I do have the QA1 Pro Coil shocks but the the above pictures are not of my car.

 

Pictures are from here. 
http://www.markswork... painted 31.htm

Edited by ls2lxhatch, 10 December 2015 - 08:09 PM.

[ls2lxhatch]

I agree they do not look strong enough but according to the engineering report they are stronger than the factory arms.

 

McDonald Bros have been making the arms for around 10 years. I have not heard of a lower control arm failing with the Pro Coil shocks. I have heard one report of the ball joints coming loose in a McDonald Bros upper control arm.

[ls2lxhatch]

Extract from the engineering report on the HQ-WB version.

 

Investigation
It was decided that due to the complex nature of the parts construction and design that a destructive test was the most suitable method to establish the structural properties of the subject part.

A fixture was made to support the subject part horizontally similar as it would be installed in a vehicle. A force was applied to the subject part as it would be by the coil spring that reacts on the lower arm to support a vehicles weight.

Test Result
As observed the lower arm could absorb over 3600kgs of load without the failure of the structural tubes. The load cell reached it limits before the structural tubes had bent (i.e. the graph does not level out so suggesting the structural yield of the arm). The flat plate insert did distort, but not in a manner that would result in a failure of the suspension. A minor reduction in ride height may result, but no worst. 
 
Based on the load diagram above it can there be established that a for a load of 3600 kgs at the coils spring seat a resultant ball joint will support a load of 3600 kg x .205 m 1.385m = 1916 kgs.

Hence a pair of arms will support a load of over 3832kgs without failure. Based on a recognized safety factor of 3 for the shock loadings that may be experiences in the life of the suspension, would yield a load rating of 1277 kgs.

 
It you were to fit 600 lb/in springs at standard ride height you have about 2" of spring travel before the arms are on the bump stops. This would give a maximum load at the spring mounts of around 600 kg. It the car was lowered then the maximum load would be reduced.

Edited by ls2lxhatch, 10 December 2015 - 09:50 PM.

[Bigfella237]

Sorry but that only tells half the story for me, they've admitted that the flat plate deforms, but that was only a single test.

 

What happens when that plate is subject to full bound and then full rebound thousands of times, or tens of thousands of times?

 

And what about shock loads, not as in shock absorber, but the jarring that occurs when you hit a pothole or corrugations?

[ls2lxhatch]

Based on a recognized safety factor of 3 for the shock loadings that may be experiences in the life of the suspension, would yield a load rating of 1277 kgs.

 

Maybe the plate will eventually fatigue, crack and fail.

 

If you are concerned then it would be easy to reinforce the plate or regularly inspect for signs of fatigue.

Edited by ls2lxhatch, 10 December 2015 - 11:48 PM.

[Bigfella237]

Just out of interest, if I were to build a jig and custom make my own control arms, what would it take to get them engineered?

 

Would I need to make a prototype of each first and have some qualified person or company do destructive tests and give me a report?

 

Would it also need to be x-rayed to assess the quality of the welding or would a visual inspection be enough (or maybe just smashing the crap out of it with a BFH to see if the welds break would do)?

 

Or could I do my own destructive tests with a hydraulic press and document it myself (video, photos etc.)?

 

Or would I just go ahead and build everything, then let the engineer look it over afterward?

 

I'm also wondering how hard it would be to modify the upper spring saddle area of the K-member to accept a proper full coilover instead of this weird hybrid QA1 / Viking spring?

[myss427]

I fixed mine with just a longer ball joint and have the same weight as a standard V8 Torana. You just need 1 inch extra in length to correct the issue, it also helps with geometry issues.

[ls2lxhatch]

Just out of interest, if I were to build a jig and custom make my own control arms, what would it take to get them engineered?

 

Would I need to make a prototype of each first and have some qualified person or company do destructive tests and give me a report?

 

Would it also need to be x-rayed to assess the quality of the welding or would a visual inspection be enough (or maybe just smashing the crap out of it with a BFH to see if the welds break would do)?

 

Or could I do my own destructive tests with a hydraulic press and document it myself (video, photos etc.)?

 

Or would I just go ahead and build everything, then let the engineer look it over afterward?

 

I'm also wondering how hard it would be to modify the upper spring saddle area of the K-member to accept a proper full coilover instead of this weird hybrid QA1 / Viking spring?

 

 

You would need to engage an engineer that is recognised by the DOT in your state. It is up to the engineer to decide what testing is required and at what stages the components are inspected. Testing that is required by the engineers would be need to be supervised by an engineer.

 

The NSW DOT would produce a list of recognised engineers similar to the list below produced by the WA DOT.
http://www.transport...U_VS_IB_102.pdf

 

McDonald Bros used Talk Torque Automotive (Bill Malkoutzis) for the report on the HQ-WB Wishbones.

 

There is some information about Bill Malkoutzis qualifications here.
http://www.goauto.co...A2579330004FA6E

 

This is the copy of the report I was sent via email. It is a shame the quality of the scan is so bad.
http://ls2lxhatch.co...ments/engineers report on wishbones.pdf

 

An engineer could specify that the welds are to be x-rayed on each part that is made if the design of the part made a single weld critical.
In the case of the McDonald Bros LCA the engineer concluded that welds did not need to be x-rayed.

 

 

The construction of the subject part is basically mild steel tubing, plate, and webs. The welding on the subject part is carried out with a TIG welder and of a very high quality. The design is such that there is a number of welds combined to create any one joint. Hence an error in one weld is unlikely to be repeated on the next, and so built in redundancy ensures the strength of any one joint. After testing there was no evidence of cracking or damage to any of the welds on the supplied test part.

 

This is one way of fitting a true coilover shock. The car was built by Mitchell Race Xreme who also built the Clark Hopkins Hatch. It would be interesting to find out what spring rate was fitted, the spring wire diameter looks thicker than the 760 lb/in springs.

 

More pictures here.
http://www.themotorh...7-holden-torana

Edited by ls2lxhatch, 11 December 2015 - 11:42 AM.

[MRGMH]

LS2LXHATCH. Sorry to dig up an old thread. I’m in the process of doing this now and just gathering information.

With a holden 308/355 600lb mustang qa1 spring (8inch uncoiled length)?

Chev sbc 600lb aswell or 700lb?

With the lower control arm was thinking of playing it and fully welding the part where it goes through the lca to strengthen it should suffice?

Will a qa1 pro shock, 8inch mustang spring and 600/700lb spring work well and still have adjustability for ride high to have the car sitting nice ?

Also what model qa1 pro coil over are people using? Chevell or Camaro something the like?


Thanks

[HDT166]

LS2LXHATCH. Sorry to dig up an old thread. I’m in the process of doing this now and just gathering information.

With a holden 308/355 600lb mustang qa1 spring (8inch uncoiled length)?

Chev sbc 600lb aswell or 700lb?

With the lower control arm was thinking of playing it and fully welding the part where it goes through the lca to strengthen it should suffice?

Will a qa1 pro shock, 8inch mustang spring and 600/700lb spring work well and still have adjustability for ride high to have the car sitting nice ?

Also what model qa1 pro coil over are people using? Chevell or Camaro something the like?


Thanks

how did you end up going with this

[ozyozyozy]

600-700lbs spring is way too light for the front unless you push the coilover right out to the lower ball joint, even then still a little light.

[MRGMH]

how did you end up going with this

I ended up buying a front fabricated k frame with all tubular control arms with qa1 coil overs. Not installed yet

Edited by MRGMH, 28 June 2020 - 11:35 PM.