Jump to content

Autoshite chat over Zoom - 8.00pm Tuesdays. PM brownnova for the link if you don’t have it!


Recommended Posts

2 minutes ago, brownnova said:

no topics are actually off limits

Some probably are! Think the idea though is for balance and giving everyone the opportunity to talk about something of interest to them, if they wish. When folk are passionate about a subject and get stuck into it, it can monopolise the whole session, which isn't so nice for the others if they don't find it that interesting. If we are all a bit mindful to let everyone have the opportunity to speak and be prepared to listen to them when they do, it should roll along nicely.

Link to post
Share on other sites
7 hours ago, Heidel_Kakao said:

That's literally all I would do to it. Completely original apart from the bigger engine.

Adding the 643cc engine would take the power up to 30bhp from around 20bhp for a decent 50% rise.

My gut feeling is an Invacar with its standard engine will top out around 60 ish mph and adding 50% extra power will take it up to 75ish mph. The Invacar is light weight, has a smallish width with the aerodynamics of pushing an edge on brick thought the air so is going to need quite a large power increase to get to 100 mph. I am thinking you will need 80bhp.

I would also have concerns at higher than design speeds of the air getting under the Invacar and flipping it over particularly in a cross wind at 100 mph.

Link to post
Share on other sites
1 hour ago, Six-cylinder said:

Adding the 643cc engine would take the power up to 30bhp from around 20bhp for a decent 50% rise.

 

a 660cc 650TRII engine would be a better start, as that kicks out 41Hp over the stock 19.3 :) (although a 643cc engine is probably a bit easier to get ahold of!)

or you can stick on a pair of these and go straight to 761cc :) 

https://prokschi.at/puch-500/tuning/straight-shank-piston-cylinder.html

this video even has "AC 500" in the title :) 

 

 

1 hour ago, Six-cylinder said:

My gut feeling is an Invacar with its standard engine will top out around 60 ish mph and adding 50% extra power will take it up to 75ish mph. The Invacar is light weight, has a smallish width with the aerodynamics of pushing an edge on brick thought the air so is going to need quite a large power increase to get to 100 mph. I am thinking you will need 80bhp.

Oh a stock Model 70 will do more then 60 with ease, I think @Zelandeth has well and truly proven that! :)

but I sadly dont have a verified top speed yet, iv seen a good number of reports of peopling doing about 70-80-85Mph even! but iv never seen a top speed run actually attempted and verified against a GPS etc

I would love for someone to try just so I know for my research etc and so I have good answer to given every-time im asked!

heres a bit of info from Zels thread on this subject in-fact :) 

On 10/12/2020 at 21:18, LightBulbFun said:

Love how well TPA is doing these days, I was wondering given the improvements the new cap made if she would now cruise at 70Mph, happy to hear she will :) (some video of you cruising  and over taking at 70Mph would be fun, think of all the heads it would make explode!)

(bonus points if your able to strap a couple not-a-go-pro's to the inside of the bath tub and front access hatch so we can see the CVT and front suspension work, like in that sadly potato cam resolution video of MHJ22P)

Yeah im not sure where exactly the 82Mph figure came from, and I did wonder for a while how would someone know they did 82Mph exactly when the speedo only goes up to 80Mph, but I realised a few months ago the little graduations after the 80Mph marker take it up to 86Mph! (the Large speedo fitted to the Model 70 from the end of March 1976 onward sadly does not have these post 80Mph markers LOL)

but as you say I do think (and well Hope :) it is possible, I have seen a large enough number of people mentioning getting 80Mph+ out of a Model 70 (or seeing one do 80Mph+ supposedly someone even being under taken by one when they themselves where doing 90!, not sure how accurate that last one is LOL) that I dont think it is purely an urban myth

it makes me all the more curious to see how a Model 70 fitted with something like the 41 horse power 660cc Steyr puch TRII engine would go! 100Mph Model 70? LOL (or would you just run into an aero wall? LOL)

 

all in all I do look forward to the investable vMax run :) 

 

On 10/12/2020 at 22:20, Mr Pastry said:

Ball park figures, if I've got it right - taking the frontal area as 18 square feet, weight 1000lbs, standard engine as per manual, 19bhp, and a top speed of 75 gives a drag coefficient of 0.35 which is quite good - I would be surprised if it is better than that, so 82 looks a bit optimistic with a stock engine.   At that rate 41bhp would give you 97mph, and you would need 44.7bhp to get to 100mph.   All this assumes that the gearing is correct.  

 

 

On 10/12/2020 at 23:15, LightBulbFun said:

interesting info :)  I was going to say a Model 70 Mark A weighs somewhere between 406-410Kg depending which official documentation you look at, but then I realise you do have to account for the driver!

I do wonder about engine power, I know the workshop manual's engine section is literally just the Steyr puch engine manual inserted in with the Model 70 stuff, and is NOT Model 70 specific (for example it gives specs for the 32ICS3 carb but the Model 70 uses the Model 70 specific 32ICS10 or 32ICS10T (still trying to figure that out) carb

it would be very interesting to stick a Model 70 on a rolling road and see what the result is :) 

50Hp should not be a problem apparently these Steyr puch engines are very tunable, and I think you can even fairly easily go up to 762cc with the use of some VW Boxer engine bits I think

 

if you had to engine swap a Model 70, I would go with a BMW Flat twin engine as used in 2CV swaps, as they match the original engine characteristics pretty well

something silly like a hayabusa engine or whatever bollocks I think would be just totally unsuitable 

but as above the Steyr Puch engine in the Model 70 is no slouch and is well known for being very robust and tunable so I think an engine swap would be unnecessary 

36 minutes ago, 3VOM said:

Tend to agree with the above. It will need an aero kit like a Time Attack car.

 

you where saying? :mrgreen:

20121541-4.jpg

Link to post
Share on other sites

I have seen the reports of high speed Invacars but I just can't equate getting something with poor aerodynamic much past 60 mph on 20 bhp.  I can't wait for some verified testing and will be happy to be proved wrong.

In the 1970s it took cars with 90 bhp to overcome the period aerodynamic and get to 100mph. What difference is the small frontal area of an Invacar going to have, yes it will need less power, but how much less?

Link to post
Share on other sites

You'd get a good 30hp from the blue death trap if you stuck a cone on the front of it. Aerodynamics for the win!

Then, obviously, the unmentionable is ripe for a K Series conversion.

Link to post
Share on other sites
1 hour ago, Six-cylinder said:

In the 1970s it took cars with 90 bhp to overcome the period aerodynamic and get to 100mph. What difference is the small frontal area of an Invacar going to have, yes it will need less power, but how much less?

Didn't someone show us how a 3D digital model cow fared in a wind tunnel, on the Zoom call the other week? We have dimensioned drawings of a Model 70 available... perhaps a simple, digital 3D Model 70 could be prepared and subjected to the appropriate aerodynamics modelling software?

Link to post
Share on other sites
10 hours ago, Mrs6C said:

If we are all a bit mindful to let everyone have the opportunity to speak and be prepared to listen to them when they do, it should roll along nicely.

There was a huge amount of double, even triple people talking over each other on this most recent one.  As someone who spends a significant amount of time in teleconference/videoconference meetings at the moment, it was very different to what I'm used to and difficult/impossible to either understand a lot of what was being said, or indeed to get a word in edgeways.  I know people get "passionate" about their subject matter, but there's limits.

Link to post
Share on other sites
10 hours ago, Mrs6C said:

Didn't someone show us how a 3D digital model cow fared in a wind tunnel, on the Zoom call the other week? We have dimensioned drawings of a Model 70 available... perhaps a simple, digital 3D Model 70 could be prepared and subjected to the appropriate aerodynamics modelling software?

Ah yes, that was I. I stumbled across it doing a Physics project last year.

2 hours ago, Talbot said:

There was a huge amount of double, even triple people talking over each other on this most recent one.  As someone who spends a significant amount of time in teleconference/videoconference meetings at the moment, it was very different to what I'm used to and difficult/impossible to either understand a lot of what was being said, or indeed to get a word in edgeways.  I know people get "passionate" about their subject matter, but there's limits.

Agreeing with the above on this. At times it did get a bit painful and hard to understand what was going on.

Link to post
Share on other sites
10 hours ago, Ghosty said:

I now have 'Size of a Cow' by The Wonder Stuff stuck in my head. 

"Me I like to think, that life is like a drink, and I'm hoping that it tastes like bourbon"

You're welcome.

Link to post
Share on other sites
2 hours ago, Talbot said:

There was a huge amount of double, even triple people talking over each other on this most recent one.  As someone who spends a significant amount of time in teleconference/videoconference meetings at the moment, it was very different to what I'm used to and difficult/impossible to either understand a lot of what was being said, or indeed to get a word in edgeways.  I know people get "passionate" about their subject matter, but there's limits.

What tends to happen *I think* is people start out with the best of intentions - just chipping in the odd word here and there, hoping that the incumbent will give up the floor.  Then, when that doesn't work, they'll talk the odd sentence over someone in the feint hope that their mic is a bit louder and the software will "cut" to them.  Then, when that still doesn't work, they either just talk across each other or give up.

I've only sat in on the one which I did enjoy, but there was one member who was clearly keen to answer a question that I'd asked him - before we were off and away on another thread.  I don't think either of us said another word all night!

Verdict: Dunno.  Maybe it's not possible to have 20 odd people in a conversation on any platform - even in real life.  Maybe folks would do well to remember they have two ears and one mouth.  It seems silly and self defeating to have an "agenda" and "chairman" so perhaps it'll always be four or five people talking over each other with the rest trying to keep up.

All that said, I did enjoy the one I came in on and would dip in again if I was around.

Link to post
Share on other sites

BRAIN DUMP... 🤪

The Invacar has a Steyr flat-twin engine.  It is shared with the Steyr-Puch 500/650 (based on the Fiat 500).

The Citroen 2CV engine (also a flat-twin) has been fitted to at least one S-P 500.  Proof of concept.  Can't find the pic, though.

Whatever.  Should be able to persuade one into an Invacar.

VGS in Belgium makes big-bore kits to expand the 2CV engine to 720, 760, 800 or 850cc.  Sparrow Automotive in Hereford supplies, builds and fits these.

Sparrow also fits BMW flat-twin motorcycle engines to 2CVs...

🤔

Link to post
Share on other sites
12 hours ago, Six-cylinder said:

In the 1970s it took cars with 90 bhp to overcome the period aerodynamic and get to 100mph. What difference is the small frontal area of an Invacar going to have, yes it will need less power, but how much less?

Urgh.

Frontal area of an Invacar is approx 1.0m2.  It's not exactly that, but I've no drawings to work from.  I base that on 1.0m high and 1.0m wide, allowing for being wider at the bottom than the top.

The drag of an invacar will be comparatively very high, as the rear window design destroys a lot of the smooth airflow.  I'd guess that the cd is somewhere around 0.6 at the speed we're talking about.  Aerodynamics were not a feature of the design.

100mph is 45m/s.  Air density 1.2kg/m3

Force needed to achieve 100mph is (0.5)(cd)(density)(area)(velocity2) = 0.5 x 0.6 x 1.0 x 1.2 x 45 x 45 =  729N

Work done per second is then 729N x 45m = 32,805 Joules.  And as we've done that over a second, that's also the number of Joules/second, or watts.

So it'll need most of 33kw (44 bhp) to hit 100mph, allowing only for wind resistance (which is the largest factor).  Add in some rolling resistance and some gearbox/tyres losses, and you'll probably be closer to 40kw needed,(54bhp).  And that's only if you exactly match the gearing of maximum power of the engine to the speed you want to achieve.  Real world says a 60bhp engine.

WIth more accurate information regarding the frontal area and the cd at the speed we're looking at, that could be done more accurately, but for the moment, close enough.  The 0.6 is taken from the fact that a Ford Anglia (also with a terrible rear window design) is 0.52 as noted here, and I don't think an invacar is as good as that, not least due to having a flat windscreen.

Link to post
Share on other sites
4 hours ago, Talbot said:

Urgh.

Frontal area of an Invacar is approx 1.0m2.  It's not exactly that, but I've no drawings to work from.  I base that on 1.0m high and 1.0m wide, allowing for being wider at the bottom than the top.

The drag of an invacar will be comparatively very high, as the rear window design destroys a lot of the smooth airflow.  I'd guess that the cd is somewhere around 0.6 at the speed we're talking about.  Aerodynamics were not a feature of the design.

100mph is 45m/s.  Air density 1.2kg/m3

Force needed to achieve 100mph is (0.5)(cd)(density)(area)(velocity2) = 0.5 x 0.6 x 1.0 x 1.2 x 45 x 45 =  729N

Work done per second is then 729N x 45m = 32,805 Joules.  And as we've done that over a second, that's also the number of Joules/second, or watts.

So it'll need most of 33kw (44 bhp) to hit 100mph, allowing only for wind resistance (which is the largest factor).  Add in some rolling resistance and some gearbox/tyres losses, and you'll probably be closer to 40kw needed,(54bhp).  And that's only if you exactly match the gearing of maximum power of the engine to the speed you want to achieve.  Real world says a 60bhp engine.

WIth more accurate information regarding the frontal area and the cd at the speed we're looking at, that could be done more accurately, but for the moment, close enough.  The 0.6 is taken from the fact that a Ford Anglia (also with a terrible rear window design) is 0.52 as noted here, and I don't think an invacar is as good as that, not least due to having a flat windscreen.

I still think an Invacar to go 100mph will need a lot more power.

I base my estimation on the power and top speed of other cars of the era.

A reliant Riato with 40 bhp can manage 80 mph

Bond Bug with 31 bhp 76 mph

Citroen 2CV 29 bhp 68 mph

Triumph Dolomite 1850cc 90 bhp 100 mph

This has a wide number of variations making an exact prediction difficult.

The one we can follow the progress of is the Classic Mini

MK1 848cc 34 bhp 75 mph

1976 Mini 1000 39 bhp 82 mph

1967 Mini cooper 997cc 55 bhp 88 mph

1998 Mini Cooper 62 bhp 92 mph

1971  Mini Cooper S 76 bhp 97 mph

As I would expect the higher the speed requires an exponential increase in bhp.

The only cd figure I can find is for the 1998 Mini at .48 Cd

Width 54 inch for the Invacar and 57.5 inch for the Mini

Height 56 inch for the Invacar and 53.5 inch for the Mini

Length 117 inch for the Invacar and 120.5 inch for the Mini

Weight 400 Kg for the Invacar and 620 Kg for the Mini

 

I have also included the dimensioned drawings

I like this project @Heidel_Kakao, just how many bhp do we need to get to 100mph, does the Invacar cut through the air much more cleanly than I imagine? 

Starting with a speed trial for standard Invacars!

Dimension diagram.jpg

Link to post
Share on other sites
49 minutes ago, Six-cylinder said:

As I would expect the higher the speed requires an exponential increase in bhp.

It's a cube law.  Assuming *everything* else remains fixed, the maximum speed of a car (or indeed any body in a fluid experiencing drag) is related to the cube of the power available.

To go double the speed requires 8 times the power.  Makes sense, as a car that can achieve 100mph might need 80bhp.  To make that same car do 200mph will need 640bhp.

53 minutes ago, Six-cylinder said:

The only cd figure I can find is for the 1998 Mini at .48 Cd

Remember that the cd of a complex shape is not fixed.  It varies as the flow rate increases.  There's usually a low at one point, which is the figure that most manufacturers claim.  The cd will be higher at low speeds (which is fairly irrelevant), and will also be higher at high speeds where you get changes in flow patterns.

Looking at those picures, I may have under-estimated the frontal area.  it looks like maybe an average of 1100mm wide, and possibly 1200 tall, taking into account the frontal area of the wheels too.  That would make 1.32 m2, upping the wind resistance figure to 962N and the power to 43kw (57bhp) for wind resistance only.  With some gearbox/tyre/diff losses, that might be 50-55kw (67-73bhp).  Quite a bit closer to your figures for a Mini.

 

Link to post
Share on other sites
22 minutes ago, dozeydustman said:

I’m pretty sure my dad’s disco 3 will easily top a ton. It shifts for something weighing nigh on 3 tonnes

Can confirm.
I wasn't driving it, but I definitely noticed everything was going past quite quickly which prompted me to look over at the speedo... 

0ee.jpg

This obviously took place on a closed runway. Obviously.

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...