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Esprit Turbo project car - part3 - the further continuation


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For those of you reading this sometimes things that are written come across not as intended. I have called Dave Changes today and had a long chat. He has a vast amount of experience with these engines

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Looking forward to seeing these Fabian.  Do you think they will be strong enough to hold the skis when driving?

 

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The skis on this home made ski rack (circa 1990) were fine on mine at speeds up to about 110mph on the autobahns through Germany and down to Basel. You can see how my rack holds the skis in just about the most aerodynamic position possible for when strapped to the roof of a moving car.   By their very nature skis edges are very sharp and scratchy and Fabian's racks, as they match the FYEO design, will present quite a large surface area of the ski bases to the wind as the car moves along, especially as the Olins Fabian is using are 2 metres long. I'm not suggesting that the racks would break, but I suspect the skis, which are designed to flex so you can turn on them, will move around a fair bit in the wind at anything over 30mph and the edges and heels of the skis will scratch the paint on the rack. That would be a real shame given all the work that's been done on this and I'd suggest the  skis would be best left off the car if any high speed driving is planned because the paint will get damaged, though I'll be happy to be proved wrong.

 

 

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Normally Aspirated - and lovin' it!

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I'd add that the skis may commence flexing in a cyclical manner once driven by wind forces, as they will not have any dampening of consequence. Speed at which this becomes a concern would be proportional to the overhang length of the skis. Things will get out of hand quickly If flexing is amplified via harmonic.

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1 hour ago, PhilW said:

Looking forward to seeing these Fabian.  Do you think they will be strong enough to hold the skis when driving?

 

The top of the tail fin on a 747 is made of fiberglass. It can take the loads at over 640 mph. But its aerodynamic and doesn't have two meter long slalom skis in the airflow. I think the upper metal bracket I intend to use will be strong enough. But there will be an enormous strain at speed on the whole thing. I intend only to fix them for use at slow speeds. I may however have a go on a test track and try at higher speeds. I wonder if they tried high speed in the movie.

I'm currently trying to think how to attach the lower racks.

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13 minutes ago, Lotusfab said:

 I wonder if they tried high speed in the movie.

 

From memory I don't think it gets out of 2nd gear! A gentle 30mph drive past on the road up to the hotel and a very slow U turn in front of the hotel after the ski chase. The S1 went faster especially off of the end of the pier.

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Normally Aspirated - and lovin' it!

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I could measure the exposed length of the ski, put it out the top of my wifes fiat 500 and measure the loading at different speeds with a spring balance. The drag varies with the square of the speed so much much more force  at higher velocities. Alternatvely build it and see ehat happens.

On 19/12/2019 at 17:16, ANDYR said:

Loving the look of the car, Fabian.

A controversial alternative to the fibreglass ski racks are these I made up in ploy carbonate and stainless steel.  skis held in place with rubber tree ties...

Racks drilled into car and held in place by bolting onto a large steel plate running along the underside of the top and bottom of the tailgate.  As tailgate shrinks when bolts are tightened, tube spacers are in place along the bolts to keep that gap a uniform size.

fotos show finished rear cradle and first fit to the my S3.

see you on the slopes...  :)

 

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Hi Andy, what speeds did you get to with this design?

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Once I get the first rack out tomorrow I can then move to the design. I like Andys idea above, its simple and effective. I intend to go down a Bond route.Its more  complicated but faithful to the Balsa wood props. I am hope to make a metal  bracket that sandwiches the skis in rubber, like a moder ski rack. It will be bolted to the twilgate and hold the fiberglass structure in place. It hope it will be lockable. I'll start work on a prototype tomorrow. The bottom end im thinking of another metal bracket that grabs the end of the ski in closed cell foam. We will see what happens. When you try and make some thinks it becomes obvious pretty quickly iif the will work.

I was looking through past pages on here to find Andys post. Its scary how much work I have done on this car and it still going! Engine rebuild next. 

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Easy to transport them at speed Fab, just turn them over with the tips down. There will be some force on them but none of the buffeting when the tips are up. You can then put a padded cover over them that can be tied down as well. In case you want to optimise the aero for the setup try this CFD analysis: https://www.padtinc.com/blog/gone-skiing-aerodynamics-does-it-matter-which-way-your-skis-are-pointing-on-your-roof-rack/

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7 hours ago, v8vantage said:

Easy to transport them at speed Fab, just turn them over with the tips down. There will be some force on them but none of the buffeting when the tips are up. You can then put a padded cover over them that can be tied down as well. In case you want to optimise the aero for the setup try this CFD analysis: https://www.padtinc.com/blog/gone-skiing-aerodynamics-does-it-matter-which-way-your-skis-are-pointing-on-your-roof-rack/

Really interesting. I could model this using a similar method, but I havn't got time. I need to fix it all and get it back on the road.

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Thanks. Tricky to get out of the mould. No appreciable shrinkage. Needs a lot more work to get up to standard. I need to complete the three other racks and then getvon with the mechanism. The intension is these are just fairings and the mechansim below takes all of the load. We will see what happens. I'm please how it has turned out. Failthful to the original, but so much stronger.

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Thanks to Andy(blue ski racks) I dont have to experiment with the fixing method. Im going to make nut plates to mimic the other fixings on the car. Some of the material removed to keep the weight down.

Top nut plate bonded to underside of rack with closed cell foam mounts.

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Looks fantastic Fabian, are you sending them to Neil for final paint or getting them done locally with Neil supplying the mixed paint?

Are you going to drill and secure to the Bootlid or bond with something like Sikaflex 221?
 

Dave :) 

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Do or do not, there is no try! 

 

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Hi Dave, was planing on Neil supplying the paint and my local guy to spray. Wasn't going to bond them permanently, just bolt on with nut  plates. Just about to lay up the other side. 

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Hi Fabian,

Your racks are looking great.  You've got the angles 'just so' too.  Awesome.

I easily got up to 60mph on M25 with full ski's aplomb and didn't notice anything move.  There is a slight vibration at the tips, but not, I think like a leading edge of an aircraft wing for take off :)  Funnily enough I considered testing all this out for you when I read the post last night, but travelling around Berkshire in an Esprit with skis on won't be seen by our local police as "an essential journey" in these times, so best an experiment for the wee small hours or not at all for now...

Keep in mind my skis (and those of others) are 165 length on average.  Your Olins will be 230? so x4 of those pointing into the sky might well have an effect on noise and vibration.  When I drove back on first test I also had a few cable ties pulling the skis together latching one to the other as well as the car.  Might be worth doing and you can hide the cable tie along the back of the rack so it's not seen.

I give credit to my mate Christian who suggested the tree rubber thingy.  I was going to use a whole bunch of locks and poppers but keep it simple and less moving parts to go wrong or snap undone - best way.

Fotos show the bolts. they are 6mm diamter.    I use a mixture of 70mm in length and 100mm.  The heads I chose are allen key style as they match the smaller bolts I used to affix the steel plates at the ends of the cradle.  These go through the steel tube.  Internal diameter 6mm (just over.  something like 6.05).  I got them off eBay.  easy. The steel plate is 2mm in thickness.  Poor Max Hurst had to cut from my template.  https://max500.com/  

The rubber bands are 300mm in length.  Again, 20mins on eBay and you'll find them.

When it comes to positioning the racks onto the car. the holes on the outer skin of the vehicle are 6mm (loved drilling into my pride and joy!).  These go through to the underside of the tailgate.  Are they at an absolute 90 tangent? probably not. The drill bit went through into the second layer as it was long enough and we did it all by eye.  There is enough play for the bolt to go in at a slight angle and still emerge safely on the other side.  It was here we realised the tailgate shrinks as you tighten the bolts and of course for a trip to the COOP and back, that's fine, but a long haul trip to the Alps or long term mounting the paint will crack and the body will eventually give out and perhaps part of it, your skis and the racks all fly off at speed.

I've yet to totally bolt all this in place in full.  Right now it's all mounted loosly on the car but the idea is to 'trap' the steel tubes within the tailgate; creating x4 'collars' per rack (x16 in all) that spread the load.  If needed we can spot weld the tubes to the steel plate for 'winter with' and 'summer without' ski rack options. 

You're essentially creating x4 floating racks in space ( a bit like oil rigs) with the tailgate happening to exist in the space below them.  No pressure on the tailgate.  We're going for collar lengths 2mm smaller than the tailgate distance to allow for everything to crimp and knit together nicely.

Will post some other piccies later.

I'm in awe of your engineering here.  too much for me with the engine work, but conversations like this are cool.

 

Andy

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Here you can see why the top racks were so tricky to make. They are anything but symetrical. I currently prepping the second mould. It distorted slightly so I have to use filler to correct.IMG_1225.thumb.PNG.6e913da33e73063170ab8a68c7497e38.PNG

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2nd rack finished. Will separate it tomorrow. Can't describe in words how much work has been required to get this far. The racks have taken me much much longer than anything else on the car including the engine an gearbox.. I had to take two trips to the states to chevk out the car in the museum and then several failed plugs which take ages to make. If this separates ok then theres only the two bottom ones to do. I will never ever do this again! 😫😫😫😫😫

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