alexr8
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Posts: 24
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Sept 16, 2022 19:33:58 GMT
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I have recently joined this forum and I have introduced myself on this thread: forum.retro-rides.org/thread/223009/hi-spain-renault-mazda-camperI have a Renault 8 in good condition (these days I even use it to commute twice per week). I love many things in this car, but I dislike its very uneven weight distribution. I'm wondering how much effort would take to change it from rear engined to mid engined. I'm no builder so, if anything, I'd be commissioning this conversion to a specialist. I'd love to read any comments you may feel like sharing. As far as I can see there are two possible roads for this: 1) Keep the engine longitudinal I wonder if the current power train could be used as a whole either by placing the whole gearbox upside down (relocating the drain plug) or by opening its case and flipping the gearbox internals. (I really would like higher power, but not if it comes at a much higher overall cost or overall car weight.) 2) Change to a transverse engine I'm not sure what power train would suit (late R5 or Clio?), but the idea here would be to fit a FWD car power train as a whole like it's done on different mid engined cars (the Lotus Elise and Ariel Atom used the Rover K series engines this way if I'm not mistaken), but Renault if possible. I particularly like this second idea because of its better chances to sort out interior aesthetics more in line with the original car (fit a tiny dummy rear seat row or something). I guess the first idea would involve fitting a firewall right behind the front seats to use all of the rear space as engine bay. Stupid but true, this drastically reduces the chances of being able to make this road legal in Spain. I would guess there's also a potential in between "T" option using the early R5 power train which used this configuration, but I don't know if the transverse gearbox can be made to turn the required way. Is any of this realistic or even feasible?
Here's a recent picture of my car
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alexr8
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Posts: 24
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Sept 16, 2022 19:38:36 GMT
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I've been reading this thread on uprating the R8 transmission: forum.retro-rides.org/thread/52554/renault-8-engines-gearboxes-fitThere's this post: "one problem with the UN1 box is that it would need different rear suspension,,,,,,i'm guessing the reno 8 has swing arm suspension that pivots off the origional gearbox,,,,,,,the un1 has output flanges for a driveshaft,,,,,,so semi trailing suspension would have to be made up for the car+custom driveshafts and mounts/floor=bulkhead mods to use the un1" I was totally wrong to assume all trasaxles are the same with regards to this. I wonder what implications this has.
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Sept 16, 2022 20:21:23 GMT
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Have you absolutely exhausted all other options? By which i mean are all the suspension bushes in good shape, the springs and shocks, good tyres, anti roll bars...other upgrades to fix whatever it is you don't like about the car? Converting it to mid engined seems like it's an awfully big hammer to crack a nut. I wonder if after everything you'd end up with something that's more of a race car than you'd want?
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alexr8
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Posts: 24
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Sept 16, 2022 21:09:43 GMT
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Have you absolutely exhausted all other options? By which i mean are all the suspension bushes in good shape, the springs and shocks, good tyres, anti roll bars...other upgrades to fix whatever it is you don't like about the car? Converting it to mid engined seems like it's an awfully big hammer to crack a nut. I wonder if after everything you'd end up with something that's more of a race car than you'd want? Good point. I have upgraded the shocks but haven't done anything else. I know for a fact that there's plenty of room for improvement, but I'm not really keen. I have the feeling that, in the end, it's going to handle funny because there's only so much you can do about it. Note that the engine is cast iron, therefore heavy, and the whole car (with that engine in) weighs around 750 kg. Imagine how light the front feels (is) with the engine lifting the front from behind the rear axle. This is no 911. It just feels weird. I'd like to improve the chassis rigidity at some point, but that be on top of this other idea. I don't mind average handling, I just don't like odd handling.
Also, I kind of fancy the experiment. To be honest, I had already thought about it before I bought the car. So in a sense I bought it knowing that I may end up doing it. I chose a car model with a market value sensible enough that decreasing it by doing this wouldn't be too stupid or shameful.
As for the race car consideration, well, it's light enough to make a fun track day car and as a road car it's already not very good at all, so I'm not really losing there either. I like track day cars for both road and track use and right now I no longer have one...
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Last Edit: Sept 16, 2022 21:10:55 GMT by alexr8
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Sept 16, 2022 21:34:44 GMT
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Well I drive an early beetle, so I hear you about funny handling...but saying that, decent tyres and shocks transformed my car.
But it does make me wonder if there isn't a much lighter, modern motor that could replace the original iron lump? Didn't these things get raced in period? Makes me think they can't be all that bad. Does sound like a fun idea though.
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alexr8
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Posts: 24
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Sept 16, 2022 21:55:46 GMT
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Well I drive an early beetle, so I hear you about funny handling...but saying that, decent tyres and shocks transformed my car. But it does make me wonder if there isn't a much lighter, modern motor that could replace the original iron lump? Didn't these things get raced in period? Makes me think they can't be all that bad. Does sound like a fun idea though. Yes, these were very popular for entry level racing in France and Spain. But the reason people raced them is because that's what was available. All these became obsolete as soon as other popular cars with better engine configurations became available. But you're right, it's not so bad, it's just funny in a way I don't like, ha ha.
I hadn't thought about the option of keeping the engine where it is, but using a lighter one so that the front is lifted less. It makes a lot of sense.
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alexr8
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Posts: 24
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Sept 16, 2022 21:58:54 GMT
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Speaking of bugs, people have been fitting Renault UN1 transaxles to their VW T2 vans (and I presume their bugs, too), at least in the US. With an adaptor plate... No idea why you'd want to replace the original gearbox with that, but it makes me want to put a UN1 in my R8 and mate it to a 911 engine if only to see what it does.
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Last Edit: Sept 16, 2022 22:00:16 GMT by alexr8
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scmick
Posted a lot
Posts: 1,493
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Sept 16, 2022 22:17:20 GMT
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Sept 17, 2022 2:26:32 GMT
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Sounds to me like you have your mind made up about going mid engined. I didnt find any pics of mid engined R8's, but a couple of mid engined Dauphines. But the rear engined configuration doesnt bother me. Rear engined Abarths and Simca's can still hold their own against much more modern machinery... Looking at this vid, the main problem seems to be the rear suspension geometry. Too short of a swing axle length and too high of a rear rollcenter makes the outside rear wheel tuck under. But even then, it seems pretty controllable. As long as a good front/rear weight distribution is possible, it can be a good effective handling car. The advantage over that, by going mid engined, would be a lower polar moment of inertia ( more weight concentrated towards the middle of the car, even with the same front/ rear weight distribution ).
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alexr8
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Posts: 24
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Sept 17, 2022 16:47:51 GMT
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Easiest way to get the weight distribution a bit closer to even is to do what Racing SIMCA 1000s and I think R8's had. Move the radiator and fuel tank into the front 'boot' area. My SIMCA racecar handles spot on with a big radiator piped underneath to the front (using an electric pump) and with a fuel cell above it. More capacity/airflow for the cooling too. Am currently building another one with the same set up. That makes SO much sense! Thanks for the tip.
I love the Simca 1000, there's a very tempting one advertised just now here in Spain, square headlights, no rust, great condition throughout, 8k €... tempting.
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alexr8
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Posts: 24
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Sept 17, 2022 17:01:04 GMT
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Sounds to me like you have your mind made up about going mid engined. I didnt find any pics of mid engined R8's, but a couple of mid engined Dauphines. But the rear engined configuration doesnt bother me. Rear engined Abarths and Simca's can still hold their own against much more modern machinery... Looking at this vid, the main problem seems to be the rear suspension geometry. Too short of a swing axle length and too high of a rear rollcenter makes the outside rear wheel tuck under. But even then, it seems pretty controllable. As long as a good front/rear weight distribution is possible, it can be a good effective handling car. The advantage over that, by going mid engined, would be a lower polar moment of inertia ( more weight concentrated towards the middle of the car, even with the same front/ rear weight distribution ). Hey, thanks for the picture, I'd pay to listen to the owner say what I want to hear, ha ha.
My mind is made up if I find this reasonably feasible, otherwise I'd compromise with other solutions or simply sell the car and get something else.
Re. rear geometry, most people here simply lower the rear to get the camber as negative as wanted, specially for hillclimb use, etc. That's easy to sort out. It's weird to see how much positive camber the inside rear wheel gets on the video considering that the lateral acceleration with those thin wheels can't be much at all, less so with period tyres which had so little grip.
Good stuff, guys, thanks a lot.
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Sept 17, 2022 17:28:44 GMT
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Yeah, just lowering it is the quick and dirty fix. But for better results, it gets a bit more complicated. The inside wheel goes positive because of the jacking effect which happens with the outside wheel.
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Sept 17, 2022 17:59:29 GMT
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It was easy for manufacturers to combine rear engined cars with swing axle rear suspension.
And I think that has played a big part in their reputation for their handling problems.
The manufacturers knew this.
That is why some of the later versions had better rear suspensions.
( swing axle Vs IRS VW bug's, early Vs late Corvair, 356 Vs 911 Porsche)
A rear engined car will have the pendulum effect ( because of the polar moment of inertia I talked about earlier), but that can be controlled if you anticipate it.
A car with more weight concentrated around the center will be more responsive ( on turn in, etc) , but also more twitchy.
The front rear weight distribution ( on all cars, but specially rear engined ones) is critical.
I've owned some cars that had too much rear bias ( you want something in the 40/60 to 45/55 range, with the bigger number in the back ), and were absolute undrivable in certain conditions.
One more thought on the swing axle rear geometry.
They way those were built, usually, was that the swing axle pivot point was at or near the diff centerline.
Which gave a rollcenter that was way too high.
A car with large dia wheels ( like your R8), because the diff centerline was at or close to 1/2 dia of the wheel, that problem was even worse.
( less so on a lowered car, which is why that fix works...)
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alexr8
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Posts: 24
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Sept 17, 2022 22:40:19 GMT
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Yeah, just lowering it is the quick and dirty fix. But for better results, it gets a bit more complicated. The inside wheel goes positive because of the jacking effect which happens with the outside wheel. Oh, in fact I meant the outside wheel but got confused. I can't believe the picture you just posted, it's astonishing.
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alexr8
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Posts: 24
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Sept 17, 2022 22:41:14 GMT
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It was easy for manufacturers to combine rear engined cars with swing axle rear suspension. And I think that has played a big part in their reputation for their handling problems. The manufacturers knew this. That is why some of the later versions had better rear suspensions. ( swing axle Vs IRS VW bug's, early Vs late Corvair, 356 Vs 911 Porsche) A rear engined car will have the pendulum effect ( because of the polar moment of inertia I talked about earlier), but that can be controlled if you anticipate it. A car with more weight concentrated around the center will be more responsive ( on turn in, etc) , but also more twitchy. The front rear weight distribution ( on all cars, but specially rear engined ones) is critical. I've owned some cars that had too much rear bias ( you want something in the 40/60 to 45/55 range, with the bigger number in the back ), and were absolute undrivable in certain conditions. One more thought on the swing axle rear geometry. They way those were built, usually, was that the swing axle pivot point was at or near the diff centerline. Which gave a rollcenter that was way too high. A car with large dia wheels ( like your R8), because the diff centerline was at or close to 1/2 dia of the wheel, that problem was even worse. ( less so on a lowered car, which is why that fix works...) I understand swing axle has inherent shortcomings, but so does the live axle that my Seven replica had and that worked really well despite the shortcomings being very noticeable (loss of traction, for example). But you really made a point with the historical and market views, I loved to learn how things evolved and why, thanks. I understand "more responsive but twitchier". In my experience, mid engined cars are the ones needing more wheelbase because of this. I love small cars but this time I chose a slightly bigger model just in case I decided to go do this mid engine thing. I don't like the ZCars Mini idea, for example. I suspect the original Mini handles much better. I've owned and driven on the track different cars with remarkable handling. This Locost Seven replica was very forgiving, and so is my mk1 MX-5. My Ultima had extraordinary handling but definitely required more attention despite its wider track and wide wheels in terms relative to its own weight. I would've thought that was also because it's definitely more rigid than the MX-5... but the Seven was extremely rigid for its weight, too, and both were quite low, no difference there either. Understood re. rollcenter, thanks. Some people run smaller overall diameter wheels on 13" rims. But my 4 gear box has too short ratios already. I may introduce changes to fix that one way or another. Thanks!
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Last Edit: Sept 17, 2022 22:58:12 GMT by alexr8
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16grit
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Posts: 213
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Sept 18, 2022 18:24:45 GMT
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I've owned a few 8s, and I like the look of yours. By a (perhaps not very) bizarre quirk of life, my father in law owned a yellow 8'S' back in the mid-'60s. After one grappa too many he still enjoys recounting the tale of driving it from southern Switzerland to Paris.
I digress.
The mid-engine idea starts and ends with this comment:
"I'm no builder so, if anything, I'd be commissioning this conversion to a specialist."
So...
The sense of 'weirdness' you feel when driving an 8 is often more down to the plushness of the standard suspension (and seats for that matter) rather than the engine/transmission layout itself, which only really becomes 'problematic' when you are really pushing on.
As you probably know, MecaParts in France sell all the bits to stiffen the car up, although admittedly at eye-watering prices. Changing the shocks and springs is something I'm sure you could manage yourself though. If you want more garlic, put the all-alloy Renault 16ts motor in it. This turns your 8 into a steel-bodied Alpine A110. With careful preparation this is also a conversion that you could attempt yourself, I haven't googled it but these days there is probably even a drawing online for the replacement rear engine mount that you need to fit the 16 engine into an 8, and as per above, any other bits (water pump?) can be bought from Meca.
etc..
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Sept 19, 2022 2:21:50 GMT
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Or put the R8 body on a Lotus Europa chassis ( available reproduction). The same R16 engine 16grit suggested, the desired mid engine configuration, very good suspension, and it might even be easier to get it road legal...
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alexr8
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Posts: 24
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Sept 20, 2022 17:35:34 GMT
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I've owned a few 8s, and I like the look of yours. By a (perhaps not very) bizarre quirk of life, my father in law owned a yellow 8'S' back in the mid-'60s. After one grappa too many he still enjoys recounting the tale of driving it from southern Switzerland to Paris. I digress. The mid-engine idea starts and ends with this comment: "I'm no builder so, if anything, I'd be commissioning this conversion to a specialist." So... The sense of 'weirdness' you feel when driving an 8 is often more down to the plushness of the standard suspension (and seats for that matter) rather than the engine/transmission layout itself, which only really becomes 'problematic' when you are really pushing on. As you probably know, MecaParts in France sell all the bits to stiffen the car up, although admittedly at eye-watering prices. Changing the shocks and springs is something I'm sure you could manage yourself though. If you want more garlic, put the all-alloy Renault 16ts motor in it. This turns your 8 into a steel-bodied Alpine A110. With careful preparation this is also a conversion that you could attempt yourself, I haven't googled it but these days there is probably even a drawing online for the replacement rear engine mount that you need to fit the 16 engine into an 8, and as per above, any other bits (water pump?) can be bought from Meca. etc.. Thanks Yes, it's a fine looking car thanks to who knows what previous owner. I love its correct rims, rebuilt to make them just slightly wider without messing with the bodywork wheel arches. I think I understand your point that it doesn't make sense to commission a work like this. Fair point. I was just looking to learn from you to increase the chances that my baseline proposal makes sense to the specialist builder. I can't agree that the car drives funny only if driven hard. The other day I got understeer in a damp roundabout when going to work, driving SO slow that you can consider the scenario static in terms of suspension, chassis stiffness, etc. Like 4 mph or whatever is dead slow for a roundabout ha ha. That made me understand that the car has serious inherent limitations. That any engine that actually puts out decent power will make it understeer hopelessly at bend exits, etc. I'm really surprised that your words come from someone with so much real experience driving these cars, and it somehow restores my faith, so thanks for this. Thanks for the 16 TS engine suggestion. I've looked it up and it looks sweet. More power would be very desirable. Although my current gearbox already has too short gears for the engine it's mated too... it's an endless game I suppose. I don't mind a steel body. It's very dry where I live, so those last forever. And the car is light enough anyway, partly because the sheet metal is so thin that you can damage it with your bare hands (like the rear on my one, which is slightly bent because once I had to push the car).
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alexr8
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Posts: 24
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Sept 20, 2022 17:35:59 GMT
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Or put the R8 body on a Lotus Europa chassis ( available reproduction). The same R16 engine 16grit suggested, the desired mid engine configuration, very good suspension, and it might even be easier to get it road legal... Wow, interesting!!! Like you said, this seems to tick many boxes already. Noteworthy rework tasks I see: -Shorten the chassis to match the R8 wheelbase. -Sort out a steering rack that suits (connects) both "halves" of the car: the rolling chassis and the car interior column attachment. What else? On the plus side, I would get many things automagically sorted out like gear linkage, pedals, powertrain mounts, engine-gearbox mating, etc. etc. Very nice! There used to be this really nice replica called Banks Europa, is this what you had in mind? I'm not aware of any replica kits lately.
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alexr8
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Posts: 24
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Sept 20, 2022 17:56:26 GMT
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The R16 was never sold in Spain, but the R18 Turbo was, so I should be able to buy one cheap. Same engine as the Alpine and Lotus, or at least same block. Use it as donor. Chop off the front bit of its rolling chassis and weld it in. That way I needn't worry about the power train being compatible with (or suitable for) the existing rear suspension, or what direction it turns. But yeah, maybe source a cheap R8 for that and see how it turns before ruining my nicer car. Oh, I don't know.
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