HI there!

I would like some opinions here about a thought of mine.

Tractors, or the things farmes use for on the land, can be equiped with 6-cilinders. Those engines aren't equiped with balance axes, or whatever you might call them in good english.

Those engines are part of the frame, and it makes them verry stiff right?

So, why not do that on a locost, we use a BMW six inline.
Why not bolt the entire engine to the spaceframe without rubber, the engine is fiberation free right??

Or has it been done yet?


reactions please...

Cheers
Thom

I may be wrong, but my first thought is that with the stiff suspension in the kind of cars we're building you'll vibrate the thing to pieces over time.

Tractors have biiig tyres and usually work on softer ground which I would imagine helps to dampen the vibration a lot.

Also if you've ever driven or ridden in a tractor you'll find that they're not exactly the most quiet of machines mostly thanks to everything vibrating on them.

My 2 cents worth, as I own a Tractor and locost.

My Massey Ferguson 28, yes the engine is bolted to the gearbox/back axle and they are the chassis. Tractors run at low revs, you have very low gears. Its all about low down power and torque. It has a huge "heavy" flywheel that I need a hoist to lift. My tractor never gets much above 1500rpm so with a well padded seat, low pressure in the tyres and nice soft ground the vibration is acceptable. Also with the PTO you dont want springs/suspension.

Top gear and full rev's and its a real scarry ride even on a nice smooth road.

If you ever see the Tractor Pulling monsters, well they prepapre the engine as if it was for a F1 race. Its all balanced etc as a proper race engine would be.

Mind you a friend with an old Alvis looked at the tractor and remarked how similar his engine & gearbox where !

To add to the above (as I said to Thommy in Messenger) I'd have said it may not be an issue on race cars that can be rebuilt after each race, but that would involve a fair bit of cost... but would be needed if bits weren't to fail after a short while giving it some welly on a road that isn't smooth as silk...

You are all right in that.

Just for information, I work at a farm to. I use to ride de Case CS86, quit a new puller. But when driving on the road, it's goes smooth as a baby

The large advantage of a 6 inline, v12, is that there are no secundairy viberations. ( I just quote my brother, a car engineer, who worked at ferrari, upgrading the Colombo V12)

So that's why I guess there are no damaging viberations.

I guess the main difference is that the engine is designed as a stressed member for these applications.

The Ferrari F50 is one of few road cars which use the engine as a chassis member - it is bolted directly to the bulkhead and the suspension mounted to it, but that engine was apparently based on the Formula 1 engine design.

Most of the engines which might be used in a locost were never designed for this type of stress to the castings.

engines in old cars might be similar - my old boss said the engine in his tr4a was from a tractor design

atb

steve

ok, anyway

We'll just try it, I let you know when we suceed

Unlike McLaren F1, Ferrari F50's rear suspensions are directly bonded to the engine / gearbox assembly. This means the engine becomes the stressed member which supports the load from rear axle. Then, the whole engine / gearbox / rear suspensions structure is bonded into the carbon fiber chassis through light alloy. This is a first for a road car. Advantage: lighter still. Disadvantage: engine's vibration directly transfers to the body and cockpit.

As described in the section on the chassis, the engine is also a part of the car's structure. The engine sits behind the driver, between the transmission and the tub that forms the cockpit of the car. It is the only connection between the front and back of the car. The engine is therefore called a stressed member, meaning that it carries load and is subject to mechanical stress. The level of stress that a Champ Car can exert on the frame is one more thing that makes the engine so critical to success -- the engine is, mechanically, the entire midsection of the car's structure!

The engine and drive train of a Champ Car make up about one-third of the mass of the car. In a severe crash, the engine and drive train assembly separate from the front of the vehicle at a line just behind the driver in an attempt to protect the driver and dissipate energy.
Engine stressed member
If you engine is smooth enough not to transmit overbearing vibration to the rest of the chassis it makes a lot of sense to brace you chassis against the biggest stiffest heaviest component it carries, and make use of its strength to do some of the load bearing work.

In 1963, a revolutionary chassis structure appeared in Formula One, the championship-winning Lotus 25.

Once again developed by Colin Chapman. Chapman used the engine / gearbox as mounting points for rear suspensions in order to reduce the width of his car as well as to reduce weight.

In particular, reduced width led to lower aerodynamic drag. Of course, the engine / chassis must be made stiffer to cope with the additional stresses from rear axles. Today, F1 cars still use this basic structure.

Along with the chapman strut this did find its way onto some Lotus road cars.

Although its use has been limited in Car use. It used to be a popular construction method for Motor bikes with bike like the Honda Super/Dream and the GPZ900R using the design instead of a conventional chassis.
Rescued attachment ferrariengine.jpg

quote:

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Originally posted by thommy2
ok, anyway

We'll just try it, I let you know when we suceed

---

You could also use a slight compromise -
I you look at my photos you'll see in the suspension areas and engine mounts some yellow and green looking plastic materials these are polyurethane and Green Nyloil (RS Components) machined as mounts and bushes on engine brace bars. Dampens out the vibration but des not move like rubber!

Just remember that there was an issue with Jack Hammer users getting "white finger"

What do racers get if the vibration is through the seat of the pants?

well white bum would be better than brown bum..... if you get that

mark

I believe it leads to long term stiffness - could be an advantage to some racers! lol

quote:

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Originally posted by James

quote:

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Originally posted by thommy2
ok, anyway

We'll just try it, I let you know when we suceed

---

What about just following Cymtric's chassis mods- these will double the torsional stiffness (and reduce the weight!).
This is a simple and tried and tested route.

James

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Read this thread:

http://www.locostbuilders.co.uk/viewthread.php?tid=1738

The long post by Cymtrix explains what you can do. He seems to know what he's on about (in my layman's view) and he uses a Finite Element Analysis system to work out how to make the chassis stronger.

There's a a link somewhere to a site with a picture of the mods- anyone got it as I can't find it? Thanks.

HTH,

James

look in the photo archive under cymtrix

Thanks Tim, there was also a link to a page that was presented as a Word document. A load of text at the top and a picture of the chassis below- anyone.

Cheers,

James

Yes i have a copy of that if i could work out how to attach it to this meassage i would post it anyone know how to attach a file? Unless this works....

I think it is the one you mean, 2 pages of word document, with several pictures in it

Cheers

Edit: wow it worked

[Edited on 20/2/04 by flak monkey]

[Edited on 20/2/04 by flak monkey]

Nice one that man!

Cheers,

James

A US builder is using solid mounts on his rotary engine (another with little vibration), for limited street use:

http://autos.groups.yahoo.com/group/Locost_North_America/message/14810

Another benefit of stiff mounts is more efficiency in the drivetrain for acceleration. You would save that momentary lag as the engine winds up in its mounts.

I like the compromise proposed by Rob earlier, using Nylon or the like. Best of both worlds, really, in that harmonics would be damped while most of the stiffness would be maintained.

In my opinion, solid mounts are a "racer's edge" that probably wouldn't benefit a road car too much, while the negative aspects would be noticeable. Probably a close analogy would be very stiff springing.

Pete

Tend to agree Pete. lot of racers use solid mounts - great, but there are penalties. I recently saw the havoc caused to the chassis tubes around the engine bay of a Hawk single seater (cracked welds etc.) - hence my slight compromise.
Incidentally Nyloil is very inexpensive and some of the firms manufacturing polyurethane bushes will sell you the stuff in colour coded bars/blocks - colour denotes shore rating (hardness) - . The four manufactured formulations of firmness (70, 80, 90, & 95 Shore-A) - they also can be very helpful with advice.
Cheers
Rob

http://www.focussport.com/mounts.htm

[Edited on 20/2/04 by Terrapin_racing]

[Edited on 20/2/04 by Terrapin_racing]
Rescued attachment polyurethane.jpg

The Original

engine mount standard

This is the flexible aproach



engine mount new

This will give more strucute to the engine in the space frame.

Do you guys think it'll work?

[Edited on 20/2/04 by thommy2]

I think you need to isolate the upper section from the frame. In your drawing the bolts will effectively be a solid mount.
You should use two bits of insulator - one onto the engine mount bracket and one to the frame. Then with a joint of some nature between the two pieces of PU. Mine use a dovetail.

Here is an Audi A3 polyflex bush mounting as an example
Rescued attachment a3.jpg

There was a one off 11 built in detroit in 1960 that used a slant 6 as a stressed member of the chassis. The 11 and 7 chassis' share allot in common. You can read how Colin liked the idea enough to use it in formula 1. http://www.lotuseleven.org/open_exhaust.htm

Didn't the BAR Honda team blow some engines last year because the engine flexed excessivley under the chassis load and spun the bearings.

Swindon developed a stressed engine for F3 using the ford SE Zetec block and head, and used a custom valve cover and oil pan to transmit loads between the tub and transmission. Just a thought, but cleverly designed, they could be used to triangulate the top and bottom of that huge hole we like to call the engine bay. Cheers!

P.S. Article about the engine appeared in the January 2002 issue of Racecar Engineering.

quote:

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Originally posted by drmike54
Didn't the BAR Honda team blow some engines last year because the engine flexed excessivley under the chassis load and spun the bearings.

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I have driven one and been a passenger in another race car, both of which had solidly mounted engines. Both equiped with a vauxhall 16v.
The first, a sports 2000 lola was an ally tub with subframes supporting the engine. There were a lot of vibrations through the ally tub which was very light, but required soft springing as stiffer springs just meant you'd start flexing the tub.
The second which I should be passenger in again on friday is a space frame sports prototype with the engine gearbox as completely stressed members, the rear suspension hanging off the gearbox assembly. This also vibrates a lot, things like needles on gauges and mirrors for starters. Obviously this is a race engine which is rebuilt every year minimum, sometimes more frequently. It is completey balanced (well, probably as far as a 4 cylinder can be) and the car is thoroughly checked over between qualifying & race sessions, let alone race meetings! Bolts etc always work their way loose over time. Even trusty nylocks and lock nuts need checking.

I thought about building my car with a solidly mounted engine, but I think the gain will be minimal, if noticable and the vibrations etc not worth the small gain you might get. It certainly wouldn't be comfortable for longer journeys or our bumpy roads!

You'd be better off sticking to a tried, tested and proven method of stiffening the chassis to get handling gains from the car such also reduce the unsprung mass and buy some sticky tyres!

as always, just my 2p..

Ned.

What about motorbike engines? I was thinking of solid mounting mine into the car simply because that's how it's done on the bike - is this a wise move?

Mark

hi,

In 95 (i think) I was lucky enuf to get in a f50 as a pasenger and be driven a couple of laps. wile I will always have rose tinted view of theis experince (witch was ausem) I have been toled that the vibration that can be felt get anoying on longer genys. to be honest I did not notice and was probably just shell shocked by the speed and experenced as a whole.

Blake

I will mount my engine solid into the frame like it used to be in the bike frame.
Being a single cilinder 500 cc i think i'm in for some vibe's!!!!!!!!!!!!!
My car will not be used on the road,just hillclimbing so by the time my teeth are about to shaken out of my mouth the race will be over....i hope

Single cilinder locost? Very intersting

quote:

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Originally posted by Cita
I will mount my engine solid into the frame like it used to be in the bike frame.
Being a single cilinder 500 cc i think i'm in for some vibe's!!!!!!!!!!!!!
My car will not be used on the road,just hillclimbing so by the time my teeth are about to shaken out of my mouth the race will be over....i hope

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Remember that the two method of rigidly fixing the engine can have different results an consequenses.

The first is using the engine as part of the structure of the vehicle chassis - thus the term stressed engine/gearbox etc. The engine & gearbox take direct loads in to their structure. You need to be carefull of doing this with a regular engine as they are not normally designed to handle this additional loading. The block could twist, etc. causing increased wear and possibly damage to components.

The second is solidly mounting the engine into the frame of the chassis (i.e. just leaving out the iso mounts) in a similar fashion to your average motorbike. This puts much less stress on the engine as most of it is taken up in the supporting frame around the engine. This as correctly pointed out can cause high vibration. Just be very carefull of your welding and bracket design when doing this. The vibration caused can produce high fatigue stresses in the welds and brackets themselves. You may find that you engine mount has suddenly cracked off.

Just a little food for thought.....

Aren’t most of the vibration in the vertical plane in line with the cylinders so by clever design you could isolate most of these vibrations with mountings that took the weight of the engine then with vertical mountings top and bottom you could stress the engine then the chassis twisted which is what you would want to do to improve torsional stiffness.

Well there are still just as much vibration side to side. Remember the linear motion is being turned into rotary. This is the reason for adding balance shafts, etc on some of the more expensive engines in order to reduce it and hence create a smoother running lower vibration engine.

Even if you had heavier mounts on the bottom of the engine, you would have to fix them rigid if you wanted to rigig mount on the top of the engine. Otherwise the natural movement in the lower isomount. would damage the top end which is fixed.

I am not saying dont rigidly fix an engine, but putting forward the fact that there is a little more to than whether it makes your teeth chatter.

My gut feeling would be - if you want to race your machine, rigid mounting is a viable option. If you want to use your car on the road, a lot, then isomounting is easier on the engine and your backside.

sorry for digging up an old thread, but pre war Bugatti's also had solid engine mountings.