Loosing weight

[Paul Amey]

Are aluminium engine back plates worth the expense?  Also I noticed how heavy the exhaust manifold is. Are tubular manifold's much better weight and performance wise?

Paul

[JohnD]

The bigger the item, the more weight you can save.   GRP bonnet, bootlid, are available.

Doors and roof, you have to DIY (I could make them for you, but I wouldn't charge mates prices, I'm afraid - no offence!)   A 30kg roof in steel can be 9 in GRP.   A GRP door can can weigh less than 5kgs.

The weight saving on a back plate depends on the 2.5 times lesser density of aluminium over steel.  A back plate weighs about 5kgs, so 3kgs saved.    Every little counts, but that is so very little!

The choice of alloy is critical.     I made one once, it started to crack after one season!   Don't use a 6000 alloy!     7075 "aircraft grade" or even 8000 series should be used and plate in those alloys cost 25-50% more.

[Iain T]

For normal driving no, only change it if it's damaged or not flat. 

You would loose more weight changing to an Ali rad and water pump housing, plus they are at the front of the car. Tubular manifolds do work better it depends how deep your pockets are and how high your twiddle factor is. 

I remember talking to an engineer from JW Automotive who was tasked to save some weight on one of their GT40 monocoques. After spending two weeks putting flanged holes everywhere they reweighed and saved less than 5lbs. They didn't do it again, just pick small drivers! 

Iain 

[Nick Jones]

Alloy water pump housing is a reasonable weight saving and right up front. Likewise the radiator. I wouldn’t bother with end plates. The front is too small for worthwhile saving and the rear can bend even in steel form.

Nick

[Colin Lindsay]

4 hours ago, Paul Amey said:

Are aluminium engine back plates worth the expense?  Also I noticed how heavy the exhaust manifold is. Are tubular manifold's much better weight and performance wise?

Paul

I have one for the Herald but the main reason is because the original was rusty. I have an alloy waterpump housing on the GT6, and for some reason an alloy distributor pedestal (that must have been a significant saving!) but again neither were for weight saving, just ease of maintenance and no rust. The biggest weightsaving on Heralds (and possibly Spitfires?) is an alloy bellhousing, as the cast iron version weighs an absolute ton. 

[PeteH]

4 hours ago, Iain T said:

For normal driving no, only change it if it's damaged or not flat. 

You would loose more weight changing to an Ali rad and water pump housing, plus they are at the front of the car. Tubular manifolds do work better it depends how deep your pockets are and how high your twiddle factor is. 

I remember talking to an engineer from JW Automotive who was tasked to save some weight on one of their GT40 monocoques. After spending two weeks putting flanged holes everywhere they reweighed and saved less than 5lbs. They didn't do it again, just pick small drivers! 

Iain 

Watched a programe, about getting a replica "chitty bang bang" to fly, quite apart from the hillarlity, and expense. At one point the guys where so into "weight saving". they where drilling and machining holes virtually everywhere.

Pete

[Pete Lewis]

yes but it wasn't  their pride and joy  just a project to see If .it could 

Pete

[PeteH]

2 minutes ago, Pete Lewis said:

yes but it wasn't  their pride and joy  just a project to see If .it could 

Pete

Is that not how most Triumph "projects" start out. (with holes).?😢

[Pete Lewis]

yes but we all fight to fill them in !!!

Pete

[Paul Amey]

Yes, I rectified all the holes in the floorpan earlier this year! I have an aluminium water pump housing and a hole in the old radiator, so can go alley on that. The engine backplate is damaged as some muppet has elongated the started motor bolt holes. Thanks for your help.

 

[Clive]

9 minutes ago, Paul Amey said:

Yes, I rectified all the holes in the floorpan earlier this year! I have an aluminium water pump housing and a hole in the old radiator, so can go alley on that. The engine backplate is damaged as some muppet has elongated the started motor bolt holes. Thanks for your help.

 

May I ask what you are aiming to achieve? Better balance? Trackday car?

I ask as one modification that has been done is to move the engine back in the chassis. This gives just about perfect 50/50 balance. 

[Bfg]

9 hours ago, JohnD said:

3kgs saved.    Every little counts, but that is so very little!

3kgs .. That's the same as me giving up chocolate for six months .. not so very little

[Colin Lindsay]

4 hours ago, PeteH said:

 At one point the guys where so into "weight saving". they where drilling and machining holes virtually everywhere.

I spent an incredibly boring and fume-filled day back in the late 80s / early 90s drilling large holes in the doors and inner sills of a Clan Crusader as a weight-saving exercise. It was like sitting in a cheese grater.

[JohnD]

You may have read "Journey to the Centre of the Earth" by the Crane cousins: https://kickasstrips.com/2013/12/richard-and-nicholas-crane-journey-to-the-centre-of-the-earth/

Their objective was the point on Earth furthest from the sea, hence the centre (?) and took them through Bangladesh, India and over the Himalayas into Tibet and the Taklamakan Desert!  On bikes, they were understandably obsessed with weight saving, and took it to the limit, for instance cutting off the handles of the plastic spoons they planned to eat with!

John

[RogerH]

22 hours ago, JohnD said:

 

The choice of alloy is critical.     I made one once, it started to crack after one season!   Don't use a 6000 alloy!     7075 "aircraft grade" or even 8000 series should be used and plate in those alloys cost 25-50% more.

Hi John,

the 6000 Ali Alloy series can be heat treated and in the T6, T6x, T6xx condition it becomes quite 'strong'  Not quite the same as 7075T6 but getting on that way.

Sadly many 6000 grades do not have their temper stated (the T rating) and so it is an unknown quantity.

6061 T0 is used for  a lot of tubing and can be bent easily. If you know what you are doing you could re-temper to a higher state

6000 series is used on aircraft but not usually structural.

 

Roger

[Iain T]

Aluminium 6083 T6 is probably the most common shate (a term used for thicknesses above 3mm up to about 6mm above that its plate) grade commonly used for structural parts. 

Iain 

[Nigel Clark]

If you really want to take weight from your car, think about the flywheel.

Most production car flywheels are on the heavy side to ensure smooth tickover and resistance to stalling. Lightening the flywheel allows the engine to accelerate and decelerate more quickly. Also, when accelerating, the mass of the flywheel that must be accelerated by the engine is effectively multiplied by the gear ratio. With less weight at the flywheel, engine braking on closed throttle is more pronounced.

Here's an article that gives a bit more info:

https://www.torquecars.co.uk/tuning/flywheel-lightening

The downside is that tickover may not be quite as smooth and if too much metal is removed, the strength of the flywheel may be compromised with potentially disastrous consequences.

When I installed a 2.5 litre engine in my GT6, I ditched the saloon flywheel that weighed almost 20Kg and fitted the 8Kg GT6 flywheel. Blipping the throttle certainly gives a very snappy response but I don't have a true before and after comparison to say how much effect there's been on acceleration. The car certainly flies through the lower gears, but a lot of that performance must come from the extra torque of the bigger engine. I should add that I had the engine's internals balanced, including the lighter flywheel. Driving in traffic isn't a problem.

The only downside I've found is that the engine won't idle smoothly below 800-850rpm, whereas a well set up Triumph six cylinder saloon engine should be smooth at as little as 600rpm. Small price to pay!

Nigel

[Nigel Clark]

Here's another link, which explains the effect of gearing on flywheel lightening:

http://store.uucmotorwerks.com/articles/FLYWHEEL-HOW-WORKS.htm

It's BMW related but nonetheless informative and the principles apply to all cars' flywheels.

Nigel

[JohnD]

I've no comparision to show you, but my new 2.5L in SofS has a 5kg (!) Tilton flywheel, and paddle clutch.  Together with a trick camshaft, it has now become almost undriveable in traffic, but the take off is phenomenal if I get the revs right!

John

[JohnD]

I refer to Graham Robson's April 2021 Classic & Sports Car article in another thread (https://forum.tssc.org.uk/topic/7910-heres-an-odd-thing/).   Therein he mentions the struggle in the earlier 60s to make the TR4s competitive.   Even the Works Team could not lose more than 45 kgs after two years of trying!

 

[DanMi]

if you really need to lose weight probably a diet for the driver will be the most effective. (slightly tongue in cheek!) at the end of the day if you want a fast car Honda s2000s are great and pretty cheap a triumph from 40-50 years ago really isn't going to be fast by modern standards unless serious money has been spent.

[GrahamB]

Reminds me of cycling with a colleague who claimed he had saved 2 oz by filing down the gear change mechanism.  Looking at him I guessed that he was 2 stone overweight.

[Paul Amey]

Thanks for everyone's advice. No I'm not after super performance etc or intending as competition car. I just want to use the best components and turn out out a  nice car mechanically.

Paul