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Learning how to build Lotus Seven replicas...together!
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PostPosted: September 19, 2020, 12:08 am 
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Turns out that C6 Z51 drive shafts fit the output splines of the TR6070 box, which is an unexpected bonus as I can put off upgrading the rear drive hubs to C7 units until I have put a few miles on the test mule. Unlike the C7 units the C6 driveshafts are equal size, which can contribute to diff destroying wheel hop.

After reading the IMechE paper by Steve Randle about the concept and design of the McLaren F1 suspension systems* I was hoping to achieve a steering ratio of 18:1. However reviewing the Titan datasheets for "off the shelf" pinions and racks has resulted in going for the middle of the road ratio using the 8T 14 DP pinion in an eccentric rack, gives a steering ratio of 17.5:1. Changing to the 9T 14DP will give 15.5:1 and 7T 14DP will give 20:1. The eccentric housing allows the pinions to be changed without too much hassle.

Initially I felt that slower steering might be best for a manual steering setup in a very fast car, to reduce the sneeze and crash effect, however given the car will be a daily driver and used in the legal speed range slow steering may not be desirable, given it may have a tendancy to step out with 688nm on tap and need to be caught midswing.

Tire stiffness has a large effect on steering feel so lots of room for development**

Attachment:
Steering geometry top view.jpg
Steering geometry top view.jpg [ 83.42 KiB | Viewed 2445 times ]


* - IMechE paper C466/007/93
** - the process of throwing money at problems until they go away


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PostPosted: September 23, 2020, 5:34 am 
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Since the Auckland harbour bridge was damaged and commuting has been a chore I took the scenic way to work this morning. Lots of quiet country roads to allow recording of the ignition advance curve for the stock Honda ECU at 100% throttle, up some reasonable inclines to give a decent resistive load and thus a longer sampling window, using an OBD2 scanner/logger. It seems the ECU reverts to these values once more than 25% throttle is used. Interesting to see the effect of the VTEC on the advance required.

Attachment:
J35Z2 ignition advance curve.jpg
J35Z2 ignition advance curve.jpg [ 67.79 KiB | Viewed 2364 times ]


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PostPosted: December 8, 2020, 6:23 pm 
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Day job has sucked up all project time hence the lack of updates - no significant progress worth sharing.

However just completed this job for a client, replicated a Zakspeed style brake caliper. Scanned dimensions using a CMM, then modelled the part in Solidworks to fit the point cloud, 3D printed some patterns and investment cast the result. Luckily the client is patient.

Original part;
Attachment:
Zakspeed_Ford_Capri_Turbo-036.jpg
Zakspeed_Ford_Capri_Turbo-036.jpg [ 150.08 KiB | Viewed 2126 times ]

Details here; http://www.speedhunters.com/2013/02/fir ... ate-capri/

Replicated part;
Attachment:
Caliper CMM scan overlay.jpg
Caliper CMM scan overlay.jpg [ 80.06 KiB | Viewed 2126 times ]

Attachment:
Caliper model outer.jpg
Caliper model outer.jpg [ 102.4 KiB | Viewed 2126 times ]

Attachment:
Caliper print.jpg
Caliper print.jpg [ 1.09 MiB | Viewed 2126 times ]

Attachment:
Caliper castings.jpg
Caliper castings.jpg [ 499 KiB | Viewed 2126 times ]


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PostPosted: December 9, 2020, 1:25 am 
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Joined: August 10, 2019, 2:06 am
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Location: NZ
Wow, nice work there!


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PostPosted: December 9, 2020, 11:31 am 
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Location: Carlsbad, California, USA
Yeah, pretty darn cool.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: December 14, 2020, 5:14 am 
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YouTube research has uncovered an interesting implementation of twin radial engines (325 HP each), the Kamov KA 26 dates from 1969-1985. The engine crank output is turned 90 degrees by a bevel gear set to an output flange that incorporates rubber isolators, which then drive the input shafts of the main gearbox. Has to be the ugliest helicopter in the world, but has logged 1000's of hours, and it appears many are still flying in Hungary.

This one probably won't fly again but all the transmission components are there to see;
Attachment:
Kamov KA 26.jpg
Kamov KA 26.jpg [ 475.28 KiB | Viewed 1999 times ]


Startup is hilarious as being a radial engine the oil seeps into the lower cylinder when stationary. Firing up procedure is typically rotating by wrench until the cylinder is purged, then run up with compressed air until ignition is sustainable. Its amazing the spark plugs can clear the intense fouling...
https://www.youtube.com/watch?v=myyDoekcf50&t=...


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PostPosted: December 23, 2020, 7:33 pm 
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Love the smell of MDF in the morning...

Cutting out some dummy wheels - they will place the C6 spindles at the correct ride height and allow for easy assessment of camber and toe changes through out suspension movement to confirm that the positions of the inner wishbone brackets as modelled in CAD also work in reality.

Attachment:
dummy wheels.jpg
dummy wheels.jpg [ 341.24 KiB | Viewed 1893 times ]


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PostPosted: December 24, 2020, 11:10 am 
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Location: Carlsbad, California, USA
You're doing some really cool stuff. I think I have CNC envy. :mrgreen:

Cheers, and Merry Christmas

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: December 25, 2020, 4:26 pm 
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Thanks Lonnie. Best wishes to you too mate. Have you ever tried a german Christmas bread called stollen? It has a seam of marzipan running down the middle, that stuff is my kryptonite!

CNC envy is common. No matter what size machine you have, inevitably the job you want to run is fractionally bigger than the bed size you currently have...

This is how I intend for the dummy wheels work, they are the same width at the base as the rim diameter so can be used to gauge toe against factory settings. I want to mock up the suspension pickups before committing the final bracket positions into the design approval document, since that is the document my certifier will judge my final build results against.

Cutout is for brake caliper clearance. The baseline is offset from the "perfect" tire outside diameter to account for the vertical deflection of the contact patch due to the relevant corner load (estimated at this stage since I don't have the final parts to load test).

Attachment:
dummy wheel.jpg
dummy wheel.jpg [ 45.14 KiB | Viewed 1811 times ]

Attachment:
Dummy wheels.jpg
Dummy wheels.jpg [ 74.12 KiB | Viewed 1811 times ]


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PostPosted: December 25, 2020, 7:26 pm 
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Reviewing a really informative exploded view of the F1 interior trim components - it's a bit daunting when starting from nothing but over the new year will begin to knock these off one by one.

Attachment:
interior trim.jpg
interior trim.jpg [ 150.37 KiB | Viewed 1800 times ]


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PostPosted: December 29, 2020, 1:26 am 
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Spent a few hours prepping the test motor for its first fireup in a few weeks. Had to understand and measure the crankshaft position sensor (CKP) signal and how the signal is produced on the 60-2 wheel, especially the angular offset between the first tooth after the gap and TDC of no.1 cylinder.

12V or 14V feed makes no difference to the output signal;
Attachment:
ckp test setup.jpg
ckp test setup.jpg [ 369.82 KiB | Viewed 1712 times ]


This is the 2 tooth gap that the ECU detects
Attachment:
ckp gap.jpg
ckp gap.jpg [ 243.69 KiB | Viewed 1712 times ]


Once the first tooth after the gap is sensed by the hall sensor the signal drops from 3.3V to zero, the falling edge at this angle is used to synchronise the ECU so that the firing of the ignition coils (Coil on Plug type using 5V signal) and injectors matches the true mechanical positions.
Attachment:
ckp teeth.jpg
ckp teeth.jpg [ 243.68 KiB | Viewed 1712 times ]

Attachment:
no tooth detected.jpg
no tooth detected.jpg [ 356.8 KiB | Viewed 1712 times ]

Attachment:
1mm gap.jpg
1mm gap.jpg [ 280.96 KiB | Viewed 1712 times ]

Attachment:
gaptooth ridge.jpg
gaptooth ridge.jpg [ 297.68 KiB | Viewed 1712 times ]


Machined the bore of a spare 4 cyl civic flywheel to suit the J35, the bolt pitch is the same but count is different (6 on civic, 8 on the V6) so only 2 bolt holes align, but they will cope OK with the cranking torque, at this stage it is only an unloaded test engine. The starter is from a J30 odyssey, it matches the civic ring gear but turns in the correct direction.
Attachment:
Civic flywheel.jpg
Civic flywheel.jpg [ 533.94 KiB | Viewed 1712 times ]


Machined some aluminium plate to make a starter motor mount as I don't have/need the transmission for the V6. It is made in 2 pieces, with an adjustment slot so that the correct ring gear tooth engagement is easily set.
Attachment:
starter adjustment slot.jpg
starter adjustment slot.jpg [ 559.13 KiB | Viewed 1712 times ]


tight fit with minimal clearance on the pinion when disengaged.
Attachment:
pinion clearance.jpg
pinion clearance.jpg [ 394 KiB | Viewed 1712 times ]


The good news is it cranks over strongly - all it needs is a support frame, fuel supply, hacked up cooling system and ignition loom to be able to generate some excessive noise and flames - will post that on youtube


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PostPosted: December 29, 2020, 2:21 pm 
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Location: Cornholio OR "Where the magic happens"
I'm in for noise and flames! 8)

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I don't know who I am, when I am somebody else.


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PostPosted: January 2, 2021, 11:15 pm 
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Splines are the most powerful tool in the CAD library, however they are VERY time consuming to control, going to have to give my carpal tunnel a rest for a few days.

Attachment:
dash detail2.jpg
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PostPosted: January 3, 2021, 12:13 pm 
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You might want to look at alternate input devices like CadMouse or SpaceBall. I can tell you after 30+ years of mousing, it does not get better with time. Physical therapy can help, but changing the way you do things is better still.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: January 23, 2021, 7:06 am 
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Good point Lonnie, I have been using a 3D connexion spacenavigator for over 15 years, using the 2 buttons on it for "enter" and "esc" to take the load off the mouse hand - also highly recommend these devices if working in CAD.

The F1 cars used VW corrado rear view mirrors, however reverse engineering from photos is not the most accurate. Unfortunately there were about 16 corrado's sold in total in NZ - so like hens teeth. If anyone has some on hand I would appreciate double checking of a few of the main dimensions. I have been modelling the body for so long that it feels like putting barn doors on the exterior, however having decent rearward visibility is a certification requirement - hence standard units in standard position.
Mirror to drivers eyeline view;
Attachment:
barn doors.jpg
barn doors.jpg [ 182.11 KiB | Viewed 1368 times ]


View of road behind vehicle (yes, I know it looks like it's on the wrong side, but NZ is a RHD country)
Attachment:
rear view mirror cl.jpg
rear view mirror cl.jpg [ 39.91 KiB | Viewed 1368 times ]


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