Quantcast

There is a new V-Twin on the market - DuroMax 713cc

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

karmarepair

Well-Known Member
HBA Supporter
Joined
Jan 13, 2011
Messages
283
Location
United States
Internal coatings will result in the surfaces being hotter. That will need a CR drop. That will reduce the cycle efficiency and power you get. I'd rather use water injection.
That is not my understanding. The Theory is they keep heat OUT of the parts. They CAN, on engines with VERY little deck clearance, reduce combustion chamber volume enough to case trouble. From the Techline site (vendor claims, so discount them accordingly, but Techline has been around a long time, and has been used by a lot of people):

POWERKOTE™ CBC-1 CERAMIC THERMAL BARRIER COATING
  • Combustion chamber coating for all metals.
    • Excellent for piston tops.
  • Thermal barrier/heat management
    • Reduces part temperature. Protective to above 2000°F.
    • Keeps heat in combustion chamber longer through the power stroke.
    • Blurs hot spots. Reduces the potential for detonation.
    • Highly resistant to thermal shock. Survives cyclic heating and cooling.
  • Increase torque and Horsepower
    • Increase combustion chamber efficiency.
    • Reduce fuel consumption.
My friend's experience with using them: HEADS 102

Bob also used water - spraying it on the outside of the radiator of his overloaded Toyota pickup! Great for getting up long grades in the dessert in the summertime.
 

pictsidhe

Banned
Joined
Jul 15, 2014
Messages
8,812
Location
North Carolina
That is not my understanding. The Theory is they keep heat OUT of the parts. They CAN, on engines with VERY little deck clearance, reduce combustion chamber volume enough to case trouble. From the Techline site (vendor claims, so discount them accordingly, but Techline has been around a long time, and has been used by a lot of people):

POWERKOTE™ CBC-1 CERAMIC THERMAL BARRIER COATING
  • Combustion chamber coating for all metals.
    • Excellent for piston tops.
  • Thermal barrier/heat management
    • Reduces part temperature. Protective to above 2000°F.
    • Keeps heat in combustion chamber longer through the power stroke.
    • Blurs hot spots. Reduces the potential for detonation.
    • Highly resistant to thermal shock. Survives cyclic heating and cooling.
  • Increase torque and Horsepower
    • Increase combustion chamber efficiency.
    • Reduce fuel consumption.
My friend's experience with using them: HEADS 102

Bob also used water - spraying it on the outside of the radiator of his overloaded Toyota pickup! Great for getting up long grades in the dessert in the summertime.
I asked Techline for physical properties such as thermal conductivity of their coatings a few years back. They replied that they not measured them! So I ran some numbers using properties of datasheeted plasma sprayed coatings as something probably in the ball park. In order to make much difference in the heat absorbtion of a piston or cylinder, these coatings would need to be fairly thick. Due to the diffusivity of the plasma coatings, the surfaces would stay hot in an engine.

It is of course possible that the Techline coatings are indeed an order of magnitude better than the kind of stuff that NASA uses and would perform as advertised, but I strongly suspect that NASA would then be using them...

I've seen a lot of claims for these coatings, but a distinct lack of objective testing.
 

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Joined
Nov 14, 2009
Messages
7,369
Location
Rocky Mountains
If somebody is going to cast aero heads for industrials, it would be worth trying to make a universal casting that has alternate bolt and pushrod patterns for several engines
Had not considered that. Thanks for the thought!. eBay (do you cap the 'e' in eBay when it starts a sentence?🤔 ) would be a cheap source of various heads and gaskets to use as patterns. don't need serviceable parts for patterns.

That somebody is not me - yet. I've been without a dry/heated place to work for far longer than I would have expected. Yesterday was the first time I've had a chance to do physical things to actively change that situation. Really felt good to make some progress toward turning a lot of CAD and ideas into real parts! 🥳
First day in several years I've actually looked forward to waking up the next day.
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
5,365
Location
US
Tipi's work on the B&S 810 may shed some light on any advantages a new head might offer. Which will be the limiting factor: combustion air/charge throughput or head cooling? The long term questions (service life of conrods, valves, valve seats, case, etc ) will take a longer time to become known.
 

karmarepair

Well-Known Member
HBA Supporter
Joined
Jan 13, 2011
Messages
283
Location
United States
I asked Techline for physical properties such as thermal conductivity of their coatings a few years back. They replied that they not measured them! So I ran some numbers using properties of datasheeted plasma sprayed coatings as something probably in the ball park. In order to make much difference in the heat absorption of a piston or cylinder, these coatings would need to be fairly thick. Due to the diffusivity of the plasma coatings, the surfaces would stay hot in an engine.

It is of course possible that the Techline coatings are indeed an order of magnitude better than the kind of stuff that NASA uses and would perform as advertised, but I strongly suspect that NASA would then be using them...

I've seen a lot of claims for these coatings, but a distinct lack of objective testing.
You are not wrong, on several levels.

This is speculation, but IF they work by blocking radiative heat transfer vice conductive, thickness wouldn't matter.

The comparative testing I've seen has been "before and after" in parts and engines. But you never hear about the failed tests. Bob did such testing of real engines, and was sold enough to keep messing with it, on a fixed income from his Navy retirement. Jake Raby uses it in the air cooled engines he builds. Only two data points, but it seems more promising than casting new heads, to me at least.

If you want to try water injection, here is a DIY approach Water Injection By Robert Mann
 

karmarepair

Well-Known Member
HBA Supporter
Joined
Jan 13, 2011
Messages
283
Location
United States
RE Coatings:


Begin forwarded message:
From: Raby Engine Development <jud@rabyenginedevelopment.com>
Subject: Re: Coatings
Date:
August 1, 2020 at 11:45:47 AM PDT
To: Ryan Young
Absolutely. All of my engines see a host of coatings by Calico. Some are proprietary, but even the basic coatings offered by Calico are great.
Jake Raby
On Sat, Aug 1, 2020 at 2:28 PM Ryan Young wrote:
Are you still sold on them? Do you still use Calico to apply them for you?
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
5,365
Location
US
(Edited-- put comment after the new post by Hot Wings in the new thread)
 
Last edited:

pictsidhe

Banned
Joined
Jul 15, 2014
Messages
8,812
Location
North Carolina
You are not wrong, on several levels.

This is speculation, but IF they work by blocking radiative heat transfer vice conductive, thickness wouldn't matter.

The comparative testing I've seen has been "before and after" in parts and engines. But you never hear about the failed tests. Bob did such testing of real engines, and was sold enough to keep messing with it, on a fixed income from his Navy retirement. Jake Raby uses it in the air cooled engines he builds. Only two data points, but it seems more promising than casting new heads, to me at least.

If you want to try water injection, here is a DIY approach Water Injection By Robert Mann
Radiative heat transfer is a small fraction inside a combustion chamber. In order to reduce it, the coating would need to stay clean...
 

karmarepair

Well-Known Member
HBA Supporter
Joined
Jan 13, 2011
Messages
283
Location
United States
There are no sellers of Harbor Freight V-twins in California. I could buy a Lycoming be easier than a 22 HP Predator.

Luckily it looks like Home Depot sells Lifans in California. Same Honda-clone sort of thing, but the more I look at the Honda spec, nearly double the starting price starts to look acceptable - real crank bearings, forged crank and rods.
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
5,365
Location
US
... but the more I look at the Honda spec, nearly double the starting price starts to look acceptable - real crank bearings, forged crank and rods.
Are you still thinking of hopping up whatever engine you get? If so, take a careful look at the Honda. There are some advantages to their one piece head-and-cylinder design, but access to the head internals/combustion chamber is tougher.
 

karmarepair

Well-Known Member
HBA Supporter
Joined
Jan 13, 2011
Messages
283
Location
United States
Are you still thinking of hopping up whatever engine you get?
To tell the truth, I've lost the bubble on WHAT I'm doing. My investigations started aimed at powering an SD-1 kit for sale up in Oregon, they morphed to powering a Graham Lee Miranda. But without space to build, I thought maybe I'd just play around with engine development, as TiPi has done, with a test stand on a trailer. I went to price engines, and found this latest issue.
====================================

I've been researching cheap and easy ways to mount the prop on the flywheel end of a Honda or Clone, that only have 3 puller bolts. I think it can be done by recruiting the flywheel securing bolt (a longer than stock version) into the scheme, although 3 bolts MIGHT be enough. Direct drive from the flywheel end reduces torsional vibration fears. For future readers new to this discussion, see TiPi's build thread for a good discussion of which end to drive from.

The next question becomes finding a relatively easy to build airframe that will fly with 25-30 HP. Tractor, parasol, aluminum tube and gusset would be idea.
=====================================

Looking at the HP and torque curves for the Honda GX690, it looks like it still has some room to grow at higher revs, so external engine mods like a bigger carb, or relatively easy swaps like a slightly more aggressive cam, might be enough, in redrive applications, to get to a realtively fancy power to weight ratio. As TiPi has noted, Hondas are relatively heavy.
 
Top