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Author Topic: The new H-75 4 cylinder engine  (Read 967 times)

Fullraceflathead

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The new H-75 4 cylinder engine
« on: March 20, 2022, 08:07:41 am »
Has anyone that owns 1 disassembled it? I'm curious about the quality. I'd love to buy 1 of these engines but the loose rocker arm fit looks to be very sloppy that I see in the various videos. This makes me question the quality of the rest of the machining in this engine. The fact that both the fan and water pump are running backwards when run as shipped is Not impressive!!! I realize the belts/o-rings can be crossed over to change direction but thats a mickey mouse bandaid approch. It seems more like a design flaw from being rushed into production without proper testing!

Adirondack Jack

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Re: The new H-75 4 cylinder engine
« Reply #1 on: March 20, 2022, 09:15:00 am »
Brought to you by the same folks who designed the boxer opposed twin with the intake manifold blocking the oil filler cap.

RedRyder

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Re: The new H-75 4 cylinder engine
« Reply #2 on: March 20, 2022, 08:38:46 pm »
I don't have one of the H75 4s.

I will say that the internal machining is amazing for the money you pay. 

If you want one made from Coles Power Models casting kits and plans you will pay a good machinist 6,000 to 7,000.

Slightly scaled down further by Jin, it is a bargain. Jin has been a leader in making affordable model gas and steam engines.

They may not be perfect all over but you will be very hard pressed find better for the money.
I have a friend that has the H74 and H75 and he loves them both. He also has a machinist built Holt from a good builder. He said Jin's engines are easier to run and more reliable.

Have you asked Jin about the possibility of getting another fan with the blades twisted the other way?

Gil

Junkologist

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Re: The new H-75 4 cylinder engine
« Reply #3 on: March 21, 2022, 08:57:13 pm »
I have an H75 and am not real impressed with it. The loose rockers can be fixed with a small set screw to secure the rocker shafts in the stand/support. The engine basically runs backwards, hence the rotation problem with the fan and water pump. My engine leaked water from the cooling manifold due to two bad solder joints. It also leaked water into the crankcase from #1 cylinder. I changed the o-ring for the wet sleeve and that fixed it. The throttle barrel is loose in the carb body, so it’s pretty hard to get a good mixture adjustment. I also had to shim the radiator up to keep the fan from hitting the shroud. The engine runs, but it does not run good and just when it gets warmed up, it runs out of gas because the tank is so small. I got this engine pretty cheap on eBay by bidding for it and I think the $1500 price from the websites is pretty steep for what I got, but maybe I got a lemon. Lol
Mike

Check out my YouTube channel here: https://www.youtube.com/user/Cletrac

Adirondack Jack

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Re: The new H-75 4 cylinder engine
« Reply #4 on: March 22, 2022, 09:46:36 am »
It does seem the rationale of “value for the money” gets a bit stretched as more complex engines means more issue stacking, but when we are talking about reverse engineering an ancient design, and they make it run backward, seemingly unaware of fans and pumps having a designed direction, perhaps it is a bridge too far?

Fullraceflathead

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Re: The new H-75 4 cylinder engine
« Reply #5 on: March 31, 2022, 12:36:16 pm »
Since the engine is running backwards that to me sounds like a serious engineering error. I’ll bet they accidentally ground the camshafts reversed and when they discovered it they already had ground numerous camshafts for production. Then to save scrapping them and tooling up for the correct ones they released the engine running backwards. This would explain why the centrifugal water pump doesn’t work because of it’s reverse rotation and why the fan is blowing in the wrong direction.  Centrifugal pump only pump in one direction. They could have easily designed it to rotate in the opposite direction if they knew in advance.
I still really like the engine but it’s these design flaws that make us the buyer the victim or Genia pig at Our Expense!!! These design flaws should have been found during pre production testing by Real Engineers Not the Customer!!!
True be known, I really doubt they have done any durability tests on any of the many engines that they offer.
 This would explain all the worn O Rings, water leaks, cylinder scoring from no piston pin retainers, leaking valves, loose bearings, short ignition life!!!
I don’t expect perfection for the price these sell for but the money they spend on packaging would have been better spent on Quality!!!

rodnoc

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Re: The new H-75 4 cylinder engine
« Reply #6 on: March 31, 2022, 02:03:05 pm »
> Since the engine is running backwards that to me sounds like a serious engineering error.
> …..
> I really doubt they have done any durability tests on any of the many engines that they offer.


It still runs, though.

My H74 needed to have the pump ‘belt’ twisted 180*.  Its fan blows out through the radiator instead of pulling air into it, but it still happily runs through each tank of gas with the pleasant exhaust note of a twin.

These are ‘model’ engines.  They are toys for gearhead hobbyists.  They are intended for display, tinkering, and occasional running.  The price point and o-rings on the pistons make that obvious.  If you guys are expecting a continuous duty cycle with B-10 engine life, then you are shopping in the wrong store.

As mentioned before, anyone who has actually made a running miniature engine (or tried to) will understand what an incredible value Jin’s engines are.

MadeForThat

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Re: The new H-75 4 cylinder engine
« Reply #7 on: April 01, 2022, 08:20:10 pm »
You are now able to buy a working 4 cylinder 12cc engine that looks amazingly similar to the full sized engine it was modeled after, for less than a Breish associated model engine. Apples to oranges, but just think about that.  Obviously the materials may not be perfect, there may not have been any edge breaking/deburring, and surprise, there may even be assembly issues. This may seem silly, but I like that some of the details aren't perfect, because I enjoy tinkering with an already functional engine and making it as "perfect" as I deem fit. Y'all wanna buy a perfect model, be prepared to pay a lot more than Microcosm prices for it.

Fullraceflathead

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Re: The new H-75 4 cylinder engine
« Reply #8 on: April 18, 2022, 09:32:49 am »
As much as I would like to purchase 1 of these Holt style engines, for the same money I can purchase the new Toyan V8. These Toyan V8’s don’t have the several Serious Engineering drawbacks! I’ve thought a lot about this and in my opinion $1,500 is better spent purchasing the New Toyan Overhead Cam V8 engine.
I’d love to have both, maybe one day.

rodnoc

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Re: The new H-75 4 cylinder engine
« Reply #9 on: April 19, 2022, 01:28:18 am »
..... Serious Engineering drawbacks!

"Serious"  :D

It’s sort of an apples versus oranges decision. The H75 copies the Holt World War-I tractor/tank engine with separated cylinders, exposed pushrods and valves (and crankshaft with the side panels removed) that can run and idle at nearly scale rpm. Many of the moving parts are exposed and visible just like the original. The Toyan is a model of nothing. It follows the concept of the overhead cam V8 design and was created in CAD and machined from stock without castings. It doesn’t appear to have an active ignition system but instead uses glow plugs, so it needs to burn model airplane fuel and idle at a very high rpm to keep the plugs hot. Other than the revolving timing belt and pulleys there isn't much to observe when it runs. The primary feedback you get from the Toyan is noise, and its sound does not replicate the loping exhaust note of a 4-stroke V8. Obviously, Toyan’s engines would be far more practical for powering an RC model than Jin’s detailed museum gems, if that is what you are after. It’s all about whatever flips your switch. :) 

Fullraceflathead

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Re: The new H-75 4 cylinder engine
« Reply #10 on: June 12, 2022, 11:37:04 am »
Hey guys in case you don't already know the H75 engine is $150 off for father's day that makes it $1,350 that's a great price I wish I could afford to jump right now and buy one. I already purchased the Toyan V8 though.

Fullraceflathead

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Re: The new H-75 4 cylinder engine
« Reply #11 on: June 20, 2022, 10:57:04 am »
EBay has several H75’s on there lately. Some are big money but some are starting very low$. I just won one for well under the latest $1350 sale price.

Fullraceflathead

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Re: The new H-75 4 cylinder engine
« Reply #12 on: June 21, 2022, 06:02:58 pm »
After watching the video of Jin running the prototype Holt copy engine it’s obvious that he has it running backwards. The original Holt engine when viewed from the back Flywheel side with the pushrodrods to the right, the flywheel rotates counter clockwise. Jin’s engine rotates clockwise from the flywheel side and with the push rods to the right. The fix would be to machine a reverse ground camshaft then the engine could be corrected which would make the water pump and fan turn in the proper direction. If you look at Jin's video closely the O-ring belts are not flipped over.

Adirondack Jack

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Re: The new H-75 4 cylinder engine
« Reply #13 on: June 21, 2022, 06:27:55 pm »
They’re in over their heads.  Same guys have re-engineered the instructions to magically do away with splash lube on the boxer engine. They’re instructing people to use two stroke, 25:1 fuel, which does absolutely nothing for the lifters or cam or rod bearings. The idiots
Deformed the intake manifold, blocking off the oil cap, so just wrote the sump out of existence.  I sold the brand new replacement for static display. It’s impossible. Another Jin design

Fullraceflathead

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Re: The new H-75 4 cylinder engine
« Reply #14 on: June 21, 2022, 06:29:30 pm »
For those of you that might be in the market for a Holt replica there’s one on eBay currently that still under $500 it ends in a day. I purchased mine on eBay for just slightly over $500 a day ago. Remember this is a $1500 engine.