7 replies to this topic

[Spherix]

Hi all,

 

I'm currently building up a bare shell and this lead me to lots of considerations regard the interior. Looking at the heater (SPI) that came with the project I bought from someone else, I was once again greeted by a leaking radiator and disintegrated foam. On top of that, I have some ideas of modifying the lower dash rail to look similar to that of a Porsche 911 and add in the dashboard vents there instead of the round ones in the current dash; that in turn made me think how useless those vents are seeing as they are powered by nothing but driving wind and can't be heated either.

 

To sum it up, I want to build a heater/blower unit that can provide the following:

- Uprated heater core to improve heat output and reliability (or at least fit back the original Mini ones)

- Uprated blower motor for higher output and controllable speeds 

- A valve system that would allow to direct the heat and/or blown air to be directed at the window, your face or your feet (not the gearstick).

 

I've set about doing some paper prototyping, and am at the point where some additional opinions would make sense.

 

Version one:

Goal: was to figure out a 3-way valve that would work with what I had in mind

Improvements to make:  It turned out to be a bit too bulky for my liking as it sits very close to the gas pedal on LHD cars and sticks out beyond the bottom dash rail, but did have plenty of space for larger heaters or blower motors (no specific sizes in mind, just larger.)

 

Red lines show the original blower/heater housing lines

 

Version two:

Goal: Seeing as the valve works as intended, I wondered how small the design could be with all components still in the car without sacrificing airflow. I haven't sourced any aftermarket parts yet, so I kept in mind the sizes of the original heater matrix, and a slimmed down mounting diameter for the original blower, as a lot of space is wasted on airflow that it doesn't need.

 

Photos show a size comparison to the original (black) and version one (brown) as well as how the airvalve is supposed to work

 

 

Improvements to make: I feel like adapting the original heater mounts is going to be a waste of time, as there are more efficient and controllable blower motors on the market; besides, if I were to move the blower motor to a new housing in the wheel arch and possibly add a 'interior filter' in there as well to stop most dust/moisture coming in to the car, I also have the benefit of moving a noise component (the blower)out of the cabin.

 

Version Three:

Goal: Create a version that I can fabricate out of metal, mount components in and test the airflow. I think I'm at the stage where I would need to source parts for the blower and the heater matrix that are uprated specs, readily available and affordable. Big choices are in the blower market, as it seems to vary a lot between single and double fan setups (as in the Mini at the moment) and not a lot of part websites show dimensions; junkyard trips are imminent.

 

Ideally I'd use the spot in the right wheel arch that currently acts as a ducting T-piece between the dash vent and blower intake to house the new blower motor, and close off the dash vent piping as that will receive fresh/warm air via the in-car blower housing in the new setup.

 

If anyone has any suggestions as what they think would be another good improvement or if I'm missing some obvious things (like, why has no car manufacturer placed blower fans in the wheel arches) I'd love to hear about them. With a bit of luck I end up with a design that can act as a kit for people to use themselves of course. 

[mab01uk]

Great idea to improve heater/blower design.....probably not much help but early Mini's had the blower fan under the bonnet (see below).....so as you say with suitable protection could the blower fan be tucked away in the wheel arch?

 

 

The first type of Mini fresh air heater (optional). Big square tin box in the usual heater position. Snail blower under the bonnet and two control knobs.
Only fitted for about a year or so in 1962 and '63 so quite a rare item.

http://www.somerford...page=page&id=98

 

Edited by mab01uk, 23 November 2020 - 03:11 PM.

[Ethel]

Heat output has a lot to do with water flow. The specific heat capacity of water is 4,200J/kg/^oC - So if your heater flows 1kg of water, which is a litre, and the temperature drops 1 degree you'll have transferred 4,200joules to make your toes toasty. As a watt is a joule per second, say it took 10 seconds then you have a 420 watt heater.

If it was your house's boiler around a metre second would be a good speed of flow, so 1/2" hose could supply a litre in around 10 seconds, 5/8" in 6-7 seconds. I've no idea what the pressure differential is across an A Series water pump! But some of those leccy replacement pumps claim 25L/min, though expect that's through bigger plumbing.

The specific heat capacity of air is very roughly 1J/kg/^oC, but 1kg of air is even more roughly a 1,000litres.

......
Lots of rough maths there that's probably not that much use

But hopefully it conveyed:


You have to put the heat in to get the heat out.

The hotter the water (everywhere), the better the heater.

Pipe sizes matter at least as much as the size of heat exchanger.

Everything else being equal (volume & temperature), there's oodles (literally millions of times) more heat in water than air.



Also note how the original centrifugal fan is eccentric in its housing. Without the housing it'd chuck air out in all directions, like sparks off a catherine wheel. The housing forms a sort of curled trumpet that goes with the direction of the fan and airflow, increasing in area to make space for the more air pushed through the fan.

Edited by Ethel, 23 November 2020 - 04:12 PM.
better seasonally appropriate metaphor

[Spherix]

Both very insightful! I've noticed a lot of the "aftermarket" or more modern heaters use larger hose diameters, that would seem to be in relation to volume (and therefore heat) displacement. A larger heater core is therefore not always the instant answer to more heat, as per your reply.

 

The slightly silly thing is that the Mini I'm building will probably never see the road in cold and wet conditions, but I'm going for "as comfortable as possible" and the mrs. tends to be cold even when it's 20+ degrees Celsius outside There's also plenty of people mentioning the standard heater is plenty in terms of heat output. Something else to consider in terms of economics is the pricing, I can find brand new heating plastic/aluminum elements for modern day cars for well under 20 euros, whereas a classic Mini one tends to start at 45-50 pounds, and I've never had one that did not leak in the 10 years of having Mini's. Still on the fence what to use in terms of heater core though, but that's the least challenging part of the housing I'd say.

 

As for the housing of the fan, I partially agree. While the housing plays a role in which way it throws the air out, the gaps on the Mini's housing seem to follow the fibbonaci sequence or another "easy" math principle. Modern day blower houses tend to look a bit more tight like a turbo or 'shell' and follower tighter clearances. I've found a complicated paper on the airflow here if you're keen; https://www.research...fig1_324036340 

 

As I'm planning to source a more modern blower mainly for the variable fanspeed control and then likely housing it in the wheel arch, I will probably mimic the housing shape it belongs to in the 'donor car' part that I'll end up picking as to not having to reinvent the wheel.  While building it all inside the form factor of the original unit seems like a fun challenge, I also appreciate a cleaner look under the dashboard hence the space savings are interesting to me.

 

Keep em coming; very helpful to prevent (or force?) me to make more prototypes   

Edited by Spherix, 23 November 2020 - 04:59 PM.

[MikeRotherham]

This is a subject that interests me a lot.

 

Firstly though I have to say that my current setup in 94 Mayfair is more than adequate. The 1 speed heater works well, is very toasty and does the job. I find the dash end vents are anything but useless and clear the side windows but only whilst the car is moving.

 

That said the setup could be much inproved.

 

I have often wondered if the Metro Mark 1 heating and ventilation could be adapted to fit in the mini. Most of that is under the bonnet though where space is very limited

 

Perhaps the blower component could be located under the wings or as part of the large connector that sits under the driver side wing.

[mab01uk]

Photos of early underbonnet Mini heater blower fans:-

 

 

 

 

[CK's mini]

I fitted a bilge blower to my midget (about £15 off ebay), did a great job of improving the blower. 

[Ethel]

I was going to suggest looking at bilge blowers 

 

Much better value than aftermarket offerings, if a tad noisier. A consideration with an external blower is whether a recirculating heater is worthwhile. Not sure the original pulling air that just emerged from the heater, via wet carpets & copilot's feet was that good an idea.

 

An external blower is likely to need existing inlet trunking adapting, or replacing, to match up bore size's - probs an advantage if you're building from scratch.

 

Ebay's a good place to do some virtual scrapyard rummaging to see what you could scavenge off other wagons. C class Mercs look likely, LDV had separate blowers too - vans tending to have shorter noses requires a different layout.

 

The difference with the Metro was no water valve, so air had to bypass the matrix to blow cold, flaps to close it off & blend air for temperature control. Made it at least as big as the Mini's, even with the under-bonnet blower.