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Heater Fan improvements

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Heater Fan improvements
#1
  This topic is about my 1968 Triumph TR250
Aphyle2012 Avatar
Aphyle2012 Silver Member Eric Pyle
Shenandoah Valley, VA, USA   USA
I've been learning how to work my 3D printer, and wondered about improving the 5-bladed fan for my TR250 heater box. Specifically, I am interested in moving more air through the box with the current motor, which is in good knick. I have found online two possible candidates, which can be scaled, mirror, and/or modified to fit the box, shaft, and motor direction. I'd like to solicit thoughts on which approach might be more productive, and suggestions on modifications. Thanks in advance!

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Michelotti Avatar
Michelotti Brad B
Marietta, GA, USA   USA
Looks like a fun and worthwhile project. I recall from my HVAC airflow classes (the brain cells that survived the parties) that increased airflow = more work produced = higher amp draw. If you're into measuring electricity, you may want to measure the amps consumed with the original fan blade, then amp consumption with the new blades. That'll give you % increase in load as a measuring stick. If you're lucky, there may be a label on the motor specifying max amp draw or watts. You could then trim the fan blades to make sure the motor doesn't exceed max amp draw & over heat.

Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Good project for printing Eric, I'm also making various parts for my GT6 and TR250 on a 3D printer. Brad has very good points, There is a lot of science to consider for air flow, but even after all the science and engineering, there will always be testing needed. In my experience, even the big aircraft jet engine manufacturers do a lot of R&D on the fan designs. You will likely have to print several designs before you settle on one that works as you wish. Sounds like a fun project, when you are successful, keep us posted. You're probably working with PLA but for the final product you may want to go with one of the less brittle filaments.

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Aphyle2012 Avatar
Aphyle2012 Silver Member Eric Pyle
Shenandoah Valley, VA, USA   USA
Thanks for the input - the current draw was in the back of my mind, for sure, and I have become a big fan of relays on these cars, instead of running high current draws directly through the switch. Nevertheless, I planned on using cheap PLA for the "drafts" of the project, switching to ABS for the final version. I will keep you all posted, for sure.

Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Good choices, PETG works nice too and has some flexibility.

Aphyle2012 Avatar
Aphyle2012 Silver Member Eric Pyle
Shenandoah Valley, VA, USA   USA
So here is prototype #1, scaled to fit the TR250/6 blower motor. Will probably print tomorrow and will post a pic.


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Turbine1a.jpg

Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Fantastic Eric,

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Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Eric, how'd you make out with your fan print?

Aphyle2012 Avatar
Aphyle2012 Silver Member Eric Pyle
Shenandoah Valley, VA, USA   USA
Not so good so far - I need to recalibrate my printer bed, it seems. Attempt #1 was with some clear PLA on a coarse (.3mm) layering. Aborted due to poor layering on several of the blades - the bottom edges are just too thin.

So I inverted the model to print a thicker edge first and switched to a "silver" PLA I had laying about. Attempt #2 started better, using fine (.1mm) layering, but some more bed adhesion issues. Abort.

Cleaned the one part of the bed, and restarted Attempt #3. Total print time is supposed to be 42 hours, but the computer that I have driving the printer is pretty good, so it will likely be less than 35 hours.

I'll check in the morning, but if I have to abort again, I'll try printing a raft first for those thin edges.

Meanwhile, I sorted out the centrifugal flow version, but found that I had to put a groove in the underside of the model to accommodate the bolts that hold the motor together. This model will have its own challenges, I am sure.

More updates soon!

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Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Keep at it. You'll get it.

Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Eric, how's your heater fan project going? That's a pretty good challenge.

Aphyle2012 Avatar
Aphyle2012 Silver Member Eric Pyle
Shenandoah Valley, VA, USA   USA
Hi - thanks for asking. I've printed up three different versions - two of the 16-blade fan and one of the turbine. The first of the fans was a mistake, as the filament spool ran out at 2/3rds height, but it still works.

I've done some free spin tests on these and the motor, but the data are incomplete as yet.

The motor with no fan spins at about 5800 rpm
With the stock fan, it spins at 3350
Short 16-blade gets about 2900
Tall 16-blade gets only 2550
Turbine gets about 2740

All fit well into housing, but some hub mods are needed to the turbine.
The turbine is also really heavy in comparison, and has a lot of inertia - it keeps spinning for several seconds after it is switched off.
There are a couple of other designs I want to try as well.

There is another issue, though, in that the turbine fits so well, there is no where for the air to go! So it needs either mods in the base of the assembly (vents?), or needs to be shorter, or mounted lower to give the air a chance to move towards the core.

I'm rigging up a discharge measuring rig using the stock housing, a box, and a hand-held wind speed gauge (I use this for balancing my SU carbs). I have not yet measured current draw yet, but that will be the 4th parameter to measure - speed, mass, discharge, and current draw. Anything that I am missing?

So a work in progress, but there is progress. I'll post some pics soon, too.

Bpt70gt Avatar
Bpt70gt Brian T
Westmoreland, NH, USA   USA
Great work Eric. Keep at it. Do you have a base line CFM or whatever measurement of the stock heater fan so you can compare? I see you have the motor free speeds.

Aphyle2012 Avatar
Aphyle2012 Silver Member Eric Pyle
Shenandoah Valley, VA, USA   USA
That is part of the testing plan. Like I stated, stock fan spun at 3350 rpm, so baseline discharge measurements will not be an issue.

In reply to # 1508396 by Bpt70gt Great work Eric. Keep at it. Do you have a base line CFM or whatever measurement of the stock heater fan so you can compare? I see you have the motor free speeds.

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