A bit more work has been done since the last post, mainly the radiator support has been fixed in place…

Here it is welded in, with the radiator laid in lose…

Here’s what the final thing should basically look like…

I’ve also been working on the exhaust system design, I’ve got myself painted into a bit of a corner due to the frame design so the exhausts need to be a bit knotty to work the way I want.  Below is the first full design, this is a 180 degree system with 1.625″ primaries and 2.5″ secondaries.  The lengths are nearly equal, but there’s a limit to what can be achieved there.

Since the last post I’ve finished off the suspension brackets and welded them onto the frame.

In a couple of the pictures you can see the radiator support mocked up in place as the next job to do.  Again the digital angle guage came in handy to straighen out the tubes at the front of the car which had been bent in a minor way due to supporting the frame on the engine stands.

You may also spot a few more tubes in the frame, now I think it’s actually getting close to being stiff enough! Ha ha!

Suspension Brackets: Measuring & Fabrication.

OK so the next job that’s needed doing is the attachment of the suspension brackets.  The suspension bracket design is such that I can use it to take out the inaccuracies of the frame fabrication.   The obvious question is how to accurately locate the suspension points when I know the frame has construction inaccuracies (as all do).  And I have no flat surface to work from having had to ditch my build table when I moved house.

The plan on how to do this was laid out in my previous post so now it was just up to executing it…

First 4 MDF panels were cut, the lower edge of each panel had been machine cut so was used as a datum. 

Next all the holes to be drilled in the templates were marked on one panel then all 4 templates were clamped together and drilled as a single item to ensure more or less exact reproduction of the holes in all 4 panels.  The locating holes were all 2mm diameter, additional 6.5mm holes were drilled to enable the panels to be clamped to the frame.

Also recently I have bought a digital protractor which looks like this one it’s accurate to 0.1 of a degree which is equivalent to 1.75mm per m.

So at the extreme rear and front of the frame the first two panels were:

1.       Centred dimensionally to the frame at those points

2.       Set at the correct heights relative to the underside of the frame at these points.

3.       Set so that the datum edges were completely parallel to each other according to the digital protractor.

4.       Clamped to the frame.

At this stage I then took a laser level that I have and aligned it to project through holes that had been drilled so that they would be visible through all 4 panels without any of the frame tubes getting in the way.

Leaving the laser level in that same position the third panel was inserted and clamped in position so that:

1.       The laser beam passed through it as well as the other 2 panels.

2.       The datum edge was parallel to the other two panels.

3.       The laser was then moved to the opposite side and aligned to pass through all three panels to verify its position was correct.  Minor adjustments were made and the process was repeated on both sides until the laser would pass cleanly through all panels on both sides.

The fourth panel was inserted as a repeat of the third panel process.

So at the end of this process the 4 panels were in place spread over the length of the car with a laser pointer beam being able to cleanly pass through 2mm holes all four panels.  Hopefully this guarantees that all the panels are in the correct position relative to each other accurate to with the diameter of the pilot holes (2mm).

 I then spent some time thinking of any other conceivable way to measure the panels to make sure that they were square to each other, parallel to each other and centred in the frame.  After being as convinced as I was going to get I moved on to the brackets themselves…

To accurately mark the required positions on the brackets I did the following:

1.       Label each hole with a letter and mark a bracket with the corresponding letter and an arrow to designate up.

2.       A 2mm twist drill was pushed through a locating hole and used to score a line along the matching bracket to designate where the hole was required

3.       Point 2 was repeated for all brackets.

4.       The marked out locations were then drilled through with the 2mm drill.

5.       Each bracket in turn was offered up to its location and its vertical position marked onto the frame for locating when welding.

6.       The 2mm holes were then taken out to their final ½” size.

The brackets can now hopefully be accurately welded in place.

By way of reference the comparing the measured bracket standout with the designed values we can see the error in the frame fabrication, so going from the front as panel 1 the values were…

Panel  Top Left  Top Right  Bottom Left Bottom Right

1      39 (35)   40 (35)    32 (28)     28 (28)

2      36 (35)   35 (35)    30 (28)     28 (28)

3      27 (35)   24 (35)    22 (28)     22 (28)

4      TBD (35)  TBD (35)   26 (28)     28 (28)

As you can see some values were spot on and others were up to 7mm out.  Thankfully this was in the range of tolerance I could fit into each bracket (just).

It’s been a long time since the last post, there has been things happening with the car, more with sourcing parts and design work rather than actual construction though.

On my last business trip to the USA I brought back with me a set of stock 2008 model Corvette wheels, yet another Bay bargain as well as the damper units previously purchased and a pair Ultra Shield Pro Road Race seats which were purchased from Vick Racing in Texas who were very nice people to deal with.

Additionally I finally got my hands on the bolt on hub units for the C5 Corvette suspension uprights using this tool I’d been able to track down the correct SKF part number and order them directly from SKF which is always going to be the cheapest way to go to get quality parts.

Combine all that together and I’ve been able to finish off the suspension design, the rear fire-wall design and have the size and shape of the fuel tank fixed.

The next job is to get the suspension brackets attached to the frame.  This is going to be interesting as I no longer have the build table the frame was built on as a flat reference surface to work from.  Also as is inevitable I know the frame is not 100% straight.  To measure how “not straight” it is, I flipped the frame over and using a laser level that projects a flat plane I was able to survey the frame at a good number of points.  Whilst the frame is only at most a few mm out of flat, it is out as I am sure most shed built creations are.

The task then is to attach the suspension brackets accurately and remove any inaccuracy in the construction of the frame at the same time whilst having no flat surface to work from.
The plan I have come up with is to produce 4 MDF templates that have been accurately marked out with all the suspension location points on them and drilled through as a single set clamped together so that each exactly replicates the others.
These templates will then be clamped to the frame at the 4 stations where the suspension brackets attach, by aligning the templates so that a laser light can shine through all the holes in all the templates from the front to the rear of the car the templates should be in the correct alignment wit one another.
Then by shining the laser through each suspension point location in turn (so that it passes through all the holes and is therefore aligned) and offering up the suspension bracket it will mark the correct pivot point with the red dot which can then be marked and drilled.  Repeat 16 times and the job will be done.

After the previous attempt at a pedal box and steering column mount I went back to the PC and had another go at the exercise.

I was able to move the pedals up 50mm, forward and to the outside of the vehicle by 40mm, the master cylinders may be too close to the windscreen in this position but they can be spaced back from the pedal box if required.

In the new position the brake and clutch pedals have 7″ of travel which should be more than sufficient.

You’ll note compared to the previous example this version has no lightening holes and is only tack welded in at this stage. This is just in case a Mk III version turns out to be required.

The steel required for the new arrangement is actually a bit less than the previous version so the weight is about the same even without all the holes. the old version is shown below…

Next on the list of things to do was make a mock-up seat to use until I buy some real ones, this has helped in getting comfortable about what it actually feels like in the car and where various bits need to go as a results.

I’ve also started the radiator support frame, Initially this was in 25 x 1.2mm EA which just felt too flimsy as part of the function of the thing will be to support the front of the body of the car, so going for the next available material meant 25 x 3mm EA which probably is over the top.

One other valuable lesson to come out of this was TIG welding galvanised steel apart from being bad for your health, is more or less impossible, the galv pops and splatters contaminating the Tungsten almost immediately.

The pictures below show the pedal box and bottom steering column mounting taking shape and mounted, as you can see from the progress pictures these parts were cut from RHS 75 x 50 x 2.5.

Even just tacked in to the car its clear this arrangement should be plenty stiff enough in supporting the clutch and brake pedal.

The throttle pedal has yet to be designed so I’ve left two bolt holes to attach this as a sub assembly to the side of the main support structure.

Getting this all assembled into the car has revealed some issues with the design…

1. The physical amount of travel that the pedals can travel through before reaching the end of the stroke of the master cylinders is huge (290mm, 11.4”), there’s no way I believe it could all be used in real life I am sure.
2. The ends of the pedals are too close to the floor of the car, I had been worried that they were going to be too high, they need to be roughly 40mm higher.
3. The face of the pedals is too far forward, allowing for the full range of motion on the pedal then when sitting in the expected driving position the pedal face too far forward by probably 100mm
4. The steering wheel is too big at 370mm diameter and will probably need to be a ‘D’ type unit.
5. The clutch pedal lightly interferes with the bottom steering column mount. This I should have realized this looking at the CAD model its clear they’re going to touch at some point in the movement.

Compounded with the above is the fact there’s not really that much room to move the pedal box further forward or higher due to the proximity of the master cylinders to the base of the windscreen.

I’ve a few ideas on sorting the pedal box issues so I don’t imagine the above will be impossible to overcome, I guess this is just typical of dozens of issues that are bound to come up through the course of the project.

To properly address most of these issues it’s become apparent I really need to source the seats I’m going to use in the car. Without these it’s going to be more or less impossible to 100% figure out where my seats are going to end up in the foot well.
 

a design aspect I’ve been working on a bit lately is the bodywork.

This is  proving troublesome as I am not in the least bit artistic and my chosen tool to date is not a ‘real’ surfacing program.  Essentially I’m not happy with most of the work done to date.  If you take a look at the picture below for example to me its pretty average…

More work definately required there, but then if you look at this…

It doesn’t look that great either, but of course in real life it looks like this…

Which is pretty darn good looking if you ask me.  So how to separate a design that IS rubbish from one that looks rubbish in CAD is clearly a problem I will need to sort out at some point.

Since the last post I’ve engaged an Engineer to review the car, he’s been and inspected the progress to date and so far so good.

To me this is a major milestone as I really pushed to get all the welding done on the main frame before he came over.

Since then there’s been spotty progress as I’ve needed a bit of a break from the project, being sent to Manila for a week on business and having to sort a few things on my motorcycle provided that, so now it’s back to the project…

One of the things you don’t realize about a scratch built project until you are there is the repetative nature of the job, i.e. for the frame, cut fit and tack weld in a tube repeat 200 times to finish, fully weld tubes repeat 200 times to finish…

Below is another example of this, this is the start of the 16 suspension attachment brackets, they’re cut from 75 x 50 x 2.5mm RHS, the holes you can see are in the base of the bracket as they mount against the frame tube. That’s 48 holes measured, marked, center punched and drilled, just counting the ones I needed to do and not the 18 I put in the wrong side of the part.

Eventulally the parts will look like this (mostly)…

There’s actually 5 different variations used but they’re not that much different from each other. As you can see most of the metal will be cut off the part before its finished.

At this stage there’s little more to do than clean the sharp edges off of the things. The plan is to leave them as is until the suspension mounting location jig has been completed. Once this is done I can then use moving the location of the pivot holes in the brackets to remove construction inaccuracies that I’m sure have crept in so far.

Next in the list of things to do is the pedal box and steering column mounting brackets. Again to be fabbed out of cut down 75 x 50 x 2.5mm RHS.

As the structural completion of the frame nears the finish it’s been necessary to take the frame down off of the rotisserie setup to turn it fully upside-down to finish off the welding, this gave the opportunity to weigh the frame once more.

The current weight of the frame came in at 240lb (109Kg), this is as I said structurally complete though there are a lot of brackets and other bits to add to the frame yet.

I set the frame on blocks to five an idea of its final running height what’s shown below is roughly 1/2″ lower than where it’ll actually run at a minimum, depending upon how it goes on the street I may need to raise it some more 4″ ground clearance doesn’t look so much all of a sudden!

One other item of progress acchieved laely is the sourcing of some damper units which came off of eBay as so much of the project has.  The guy has one set left to sell if you are interested.