Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines
The Regular Stuff: Chat, Buy, Sell, Off Topic, etc. => General Discussion - Scale Model Gas Engines - Hit & Miss - Throttle Governed - Non-Compression – etc => Topic started by: Fullraceflathead on March 20, 2022, 08:07:41 am
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I can agree to that watching the linkages connecting rods and crankshafts and flyweight governor spinning while an engine runs can be very mesmerizing
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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.
The Toyan is arguably one of the coolest available. However it does little for me as there is nothing to watch except a serpentine timing belt and pulleys which look the same stopped or at speed.
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I always thought that full floating pins were not a problem big enough to worry about as most cylinder bore scoring is due to side loading in a direction perpendicular to the crank shaft and not parallel to the crank.
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To me the more serious issue is the piston pins not being retained by anything!
The piston pins will move during running and ultimately score the cylinder walls and reduce the compression while putting loose metal pieces in the engine!
There is a video on YouTube of the H73 (single cylinder version) disassembled. This video shows the piston pin without any form of retainers. The video shows making retainers by cutting a small piece of O ring and placing it on each side of the piston pin.
This is a quick and clever way to fix this issue. I was thinking of making a small Teflon button to go on each side of the piston pin like what is done on racing engines sometimes.
I’m a Machinist and own a Lathe and Mill and have at lot of knowledge about engines and racing but many buyers will be stuck with the current Chinese design oversight and Quality issues.
It’s still a great deal but it’s best to know all the flaws before running it too much.
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Hummm, seems those who managed to score these at something a bit under half full price (after tax & shipping is added) have done rather well in this. Even though there are issues being reported, the basic unit seems as though it is basically sound, and it's just "the Devil in the Details" that has reared its ugly head, such as running backwards and the like. While disappointing from an engineering perspective, it is perhaps not the end of the world, as these were never meant to be put into actual service and run on an extended basis, but rather are just model representations of the type that will live the vast majority of their lives as static display models, for which they seem to be exemplary representations.
Just my $0.02 on the topic .... ;c)
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I'm glad to see somebody took advantage of the low bidding on these engines. Most of them have been right around the $500 to $600 range which is a great opportunity compared to the $1500 price if you buy direct.
I could never afford it at $1500.
The engine running backwards is not a deal breaker to me just a bad oversight on the Chinese manufacturing.
I want to run mine but I really want to know if there is piston pin retainers to prevent the pins from scoring the cylinder walls. Many of the other Chinese engines made don’t have the piston pins retained.
Has anyone actually checked this on the Chinese H75 engine?
Unfortunately, it has restored the original price. It has stopped now so the H75 engine auction.
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...I also feel it will be very simple to modify that centrifugal water pump. Simply by moving the outlet pipe to the other side so it would actually work in the direction it’s turning without having to flip the belt.
The existing outlet could even just be capped off with a small threaded cap which would look very realistic in my opinion.
Please submit photos when it's done.
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Thanks for the great info RedRyder! I’ll follow that.
I also feel it will be very simple to modify that centrifugal water pump. Simply by moving the outlet pipe to the other side so it would actually work in the direction it’s turning without having to flip the belt.
The existing outlet could even just be capped off with a small threaded cap which would look very realistic in my opinion.
Nice to get rid of the twisted drive belt.
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Thanks for the great info RedRyder! I’ll follow that.
I also feel it will be very simple to modify that centrifugal water pump. Simply by moving the outlet pipe to the other side so it would actually work in the direction it’s turning without having to flip the belt.
The existing outlet could even just be capped off with a small threaded cap which would look very realistic in my opinion.
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I'm glad to see somebody took advantage of the low bidding on these engines. Most of them have been right around the $500 to $600 range which is a great opportunity compared to the $1500 price if you buy direct.
I could never afford it at $1500.
The engine running backwards is not a deal breaker to me just a bad oversight on the Chinese manufacturing.
I want to run mine but I really want to know if there is piston pin retainers to prevent the pins from scoring the cylinder walls. Many of the other Chinese engines made don’t have the piston pins retained.
Has anyone actually checked this on the Chinese H75 engine?
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Wow Gil - that's a nice one - i like the open valves
and the easy starting. If this motor would be produced
in Europe it would probably cost 10000! What a nice build.
Congrats, Arnold
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I am content with the engine going the wrong way as it is much easier for me to hand start turning the flywheel clockwise.
I also bid to win this at a good price.
I would rather see them make a water pump that goes the other way which might be a lot more cost effective than re-making the camshafts. As I said before, the radiator doesn't care which way the wind blows through it.
Here is a short video showing a cold start by hand.
Gil
https://youtu.be/0z5ODiude4o
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My H75 arrived yesterday.
I removed 2 side panels and put in enough oil to just reach the bottom of the big end on the rods just like on the Coles model.
With a needle oiler, put a drop on each of the rod bearings and each rocker. You get the idea... all that moves gets oil. The radiator doesn"t care which way the wind blows through as long as it blows.
Eventually I will try it with coolant and check for leaks.
2 oz Marvel Mystery Oil in a quart can of VP 94 octane and filled the tank.
Twisted it over with a hand drill, finger tip choked it for about 1 second and she was off and running.
I shut it down after about 15 seconds and gave the flywheel a quick twist and it fired up first try.
What's not to love?!
Gil
[attachimg=1]
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I received my H-75 today in perfect condition today.
Guys if you are interested in getting one EBay is your best choice at the moment. eBay has been selling these well below the normal $1500 price. Mine was $510 and one just sold this morning for $527.
Not to many bidders is a Good Thing!!!
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Someone got a great deal on a H75 Holt on EBay for $513 plus shipping.
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When I receive mine I will take a look at the camshaft design. I doubt they pressed on the lobes to a shaft but if they did that would not be impossible to redo to correct the rotation of the engine.
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If enough people lobby for a proper cam to reverse rotation, they might. Tell stirlingkit service. Enginediy are useless
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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 $1500 engine.
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They’re in over their heads. Same guys have re-engineered the instructions to magically do away with splash lube on the boxer engine. They’re instructing people to use two stroke, 25:1 fuel, which does absolutely nothing for the lifters or cam or rod bearings. The idiots
Deformed the intake manifold, blocking off the oil cap, so just wrote the sump out of existence. I sold the brand new replacement for static display. It’s impossible. Another Jin design
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After watching the video of Jin running the prototype Holt copy engine it’s obvious that he has it running backwards. The original Holt engine when viewed from the back Flywheel side with the pushrodrods to the right, the flywheel rotates counter clockwise. Jin’s engine rotates clockwise from the flywheel side and with the push rods to the right. The fix would be to machine a reverse ground camshaft then the engine could be corrected which would make the water pump and fan turn in the proper direction. If you look at Jin's video closely the O-ring belts are not flipped over.
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EBay has several H75’s on there lately. Some are big money but some are starting very low$. I just won one for well under the latest $1350 sale price.
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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.
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..... 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. :)
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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.
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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.
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> 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.
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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!!!
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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?
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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
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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
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Brought to you by the same folks who designed the boxer opposed twin with the intake manifold blocking the oil filler cap.
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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!