Help on model engine tooling

[10K Pete]

D, I'm afraid your last paragraph is not very cohesive, especially the part about piston slap. That explanation didn't help explain the action/cause.

And I did sign my post. I always do.

Pete

 

[D&J Fitzgerald]

i guess i should understand that two people in here are pickers, first i always level my lathe, second regarding black smoke you did not read what i stated, and yes i have worked on some big towboats and yes we do run glowplugs up north here longer then thirty seconds. you missed what i stated about mini injectors no comments on diesel fuel viscosity, why can't you condemn tbat as well. I never said i was or claimed to be a machinist or did you miss that as well, or did you simply scan my post for a insult. and yes i do have alot to learn about the use of milling machinery and i certainly will, you say you have built real engines diesels and gas yet you claim there is no taper in the bores, there is actually we check three different areas of a cylinder bore for taper, i don't care whether you believe it or not, if not the case then you explain exactly why piston slap in warn cylinders always occurs near BDC but the slap stops as the piston moves up the cylinder why TAPER. This conversation is closed, if cylinders were a straight bore my friends, then they would install thw oil rings solid and unbroken, i will say it again as the piston moves up the bore the oil scraper rings compress slightly.

i have no doubt that your all experienced with lathes and mills and messurements but trust in this, when i build my pup engine the bores will be tapered slightly.

also Diesel engines are high compression the conpression it takes to burn diesel fuel is something indeed. i stated the taplin engine had a t handle to ajust the compression thats why they started, increase compression increases heat on the stroke, heat is the key to success,several modelers have issues in building and running a mini diesel because of the mini injector building it successfuly
has not been good for these people, diesel engines also require 100 times the air that a gas engine requires. they could build a seperate injector pump it is possible.
D

 

[Cogsy]

I am not sure if you are intentionally trying to troll us, however I'll give you the benefit of the doubt one last time and answer your points:

first i always level my lathe,

You suggested we use a level to drill straight holes, that's what I addressed - you also say you've just got your first lathe so your statement seems like trolling at this point.

you missed what i stated about mini injectors no comments on diesel fuel viscosity, why can't you condemn tbat as well

You seem to think we are just trying to disagree with whatever you say - we're merely pointing out your gross errors, there's a difference.

you say you have built real engines diesels and gas yet you claim there is no taper in the bores, there is actually we check three different areas of a cylinder bore for taper

Yes, we do sometimes check for bore taper in a WORN/USED engine to decide if we need to correct it or it's within allowable tolerances.

if not the case then you explain exactly why piston slap in warn cylinders always occurs near BDC but the slap stops as the piston moves up the cylinder why TAPER.

Yes, I can, and did, in my last post - side thrust induced by con-rod angle. Much higher side thrust at bottom of stroke than top creates more wear around the bottom of the cylinder, creating the dreaded taper which causes undesirable piston slap. Why create taper when it causes piston slap? (You acknowledge piston slap is caused by taper so this is a good question).

if cylinders were a straight bore my friends, then they would install thw oil rings solid and unbroken, i will say it again as the piston moves up the bore the oil scraper rings compress slightly.

Piston rings require pressure to seal. The uncompressed rings will not fit in the bores. Rings are split so they can be installed and so they provide appropriate sealing pressure on the cylinder walls - this is really basic stuff and again seems to be indicating trolling.

also Diesel engines are high compression the conpression it takes to burn diesel fuel is something indeed. i stated the taplin engine had a t handle to ajust the compression thats why they started, increase compression increases heat on the stroke,

Yes, diesels require compression to generate the heat required for combustion, that is how they work.

diesel engines also require 100 times the air that a gas engine requires.

No, they simply don't. The stoichiometric ratio for petrol is around 14.7:1 and for diesel the stoichiometric ratio is 14.5:1 , this is a difference of only around 1.4%.

If you are not simply trolling, you seem to have taken offence at people genuinely attempting to help you on your understanding of engine building and operation. We are community here that seeks to help others and share our hard-earned knowledge. Please be polite and respectful, as we have been with you.

 

[goldstar31]

Am I the first to comment about the hiperbole and the exuberance of verbosity along with a modicum of good old phillibusrering?

Daniel
You asked for advice but turned the topic from what you certainly don't know to what you certainly think that you do.
These people WERE here to help. My concern is that they may be reluctant to help in more genuine cases

Norman

 

[Jhawk]

From the Engine Builder:

The walls of the cylinder have to be strong enough and rigid enough to withstand high combustion pressures and temperatures (600 to 1,000 psi and 3,500 degrees F for gasoline engines, and up to 2,500 psi and 4,500 degrees F for diesels!). The cylinder bore also has to provide a wear-resistant bearing surface to support the piston and rings, and retain enough oil to keep the rings lubricated.

When boring and honing cylinders, installing sleeves or replacing cylinder liners, three criteria are absolutely critical for good results:


1. Bore geometry and straightness. This refers to the roundness or cylindricity of the bore (which is necessary for good ring seating and sealing), the straightness of the sides of the bore (to minimize ring flex as the piston moves up and down), and its alignment to the bore center and crankshaft. The bore must also be accurate dimensionally so the piston will fit with proper side clearances.

2. Surface finish. The average roughness, peak height and valley depth of the surface must be compatible with the type of rings that are used.

3. Crosshatch angle. Should be within a specified range for the application to provide proper lubrication and oil control.


Cylinder Bore Roundness

The rounder the hole, the less ring tension is needed to seal the piston rings. Lower tension rings are better because they reduce friction. To get a rounder hole with minimal distortion, steel torque plates are bolted to the block to simulate the bore distortion that occurs when the cylinder heads are installed.

The torque load on the head bolts tends to pucker the bore next to the bolt threads, causing the bore to bulge inward up to several thousandths of an inch. The lighter the block, the more vulnerable it is to this type of bore distortion.

If the block is bored and honed without the simulated load created by a torque plate, the bore may be perfectly round after it has been machined. But it won’t stay that way. As soon as the head is installed and bolted down, the head bolts will pull the bore out of round, possibly causing a poor seal between the bore wall and rings (especially if thin, low tension rings are used).

That’s why most performance engine builders and even many production engine builders use torque plates when they are machining blocks. Good bore geometry improves ring sealing to maximize power while minimizing blowby, compression losses, emissions and oil consumption.

How much bore distortion is too much? It depends on the application. For many late model gasoline engines with relatively tight piston to cylinder wall clearances, .0005? out-of-round may be too much. But on an older Chevy small block budget motor, higher tension rings and greater piston clearances, you might get by with as much as .005? of bore distortion.

Cylinder taper and straightness are just as important. On some late model gasoline engines, the factory specs call for .0002? (.006 mm) or less of taper. By comparison, the maximum amount of taper allowed in many older passenger car engines was as much as .010? (0.25 mm).

Too much cylinder bore taper is bad because it causes the rings to flex in and out as the piston slides up and down. Excessive taper can lead to ring breakage as well as interference problems if the ring end gap is not sufficient to handle the change in bore diameter. With gapless rings, good bore geometry and taper are even more important to minimize blowby and compression loses and to maximize the benefits provided by this style of ring.

 

[petertha]

i have a few articals on those building diesel engine models, they have problems with injectors working, perhaps the mini injectors worked just fine, but a diesel engine does require a tapered bore due to great compression required to fire the fuel.
Daniel.

Can you link home built or commercial model/small scale diesel engines you have come across employing diesel head injectors? I'm not aware of many. There is a build going on in another forum & it looks to be on the bleeding edge of micro-scale, precision tolerance, experimental stuff. Not just the injectors, but pumping & regulator ancillaries. I think if you tabulated the compression ratio across as many model engines as you cared to study, you would find quite a bit of consistency, at least among engines grouped into similar classes.

There are RC engines loosely called 'diesel engines' which is an unfortunate, bad label still being kicked around. By these I mean the Tommy bar variable compression, glow plug ignition type. These don't have head injectors, they are venturi carburated. They are kind of a nostalgia predecessor to current common RC 2-stroke glow plug engines which are essentially the same principle but +/- fixed compression. Yes, many of these have mildly tapered liner bores but AFAIK always associated with ring-less pistons. And this is one of those 'seems simple on the surface' but is actually kind of a complex interplay of liner taper, piston shape, pinch point relative to TDC, temperature, breathing...When rings are introduced into either the 2S or 4S RC engines and/or the displacement starts to increase, the liners are always parallel bore to the best of my knowledge. Aside form specialized engines, I'd be interested to know of tangible examples where this was not the case. Maybe you can provide some examples.

There is another type of 'fuel injection' model engine, but again not a diesel head injector in the full size sense. These are basically metered 'squirt' fuel delivery systems that inject into the carburetor/induction path, which is of course much lower pressure than direct head injection. The purpose here is to maintain air:fuel mixture under tough operating conditions. Specifically the RC models they power; aerobatic planes, helicopters & certain racing applications where the models get thrown around in every conceivable orientation and high G-loads that normally adversely affect low pressure or gravity fed carbs.
http://ysengines.us/products/engines/YS185DZ_cdi/default
http://ysengines.us/manuals/manuals_us/airplane/DZ185cdi.pdf

 

[Jhawk]

Forgot to include the link:

http://www.enginebuildermag.com/2012/01/cylinder-bores-machining-to-sleeving/

 

[packrat]

Getting back to your post about[Help on model engine tooling} wanting and needing a small mill, I would look at a mill/drill ether Jet or Grizzly.
Both make a good small {and big also} mill.You will also need a milling vice, R-8 collates for the spindle, drill chuck
drill bits, number, letter and fractional size, end mills, All this can run up the cost of a milling machine.....

 

[Jhawk]

Boring head, collet chuck, rotary table, hold down clamps, edge finders......... a never ending list!

 

[D&J Fitzgerald]

Thanks for your advice. On engines. i do not plan on building a Diesel engine, but have owned about ten of them.

I do have a question outside of model engine building. I am going to mill some mini gear pulleys and also i am going to build a mini metal cuting table saw. I need too mill a mandrel to hold my cutting arbor. I am not certain of which kind steel to use . i think a light alloy steel or perhaps lead steel heat hardened after milling. please make a suggestion i am all ears?

I have ordered a tooling startup.package from the little machine shop, i also ordered a Vernier Caliper with dial a six inch. I also ordered the panther engine plans, which i will study with great care and interest.

On the engine issues, i do not like direct bores i prefer slide in or pressed in liners. I need to learn how to use my lathe now. my lathe arrived a week or so ago, guess what, it came with the wrong motor in it and rust, i bought it new, then sent a used one. I went to turn it on and the toothed drive belt was so loose that the chuck did not spin at all, when i took the motor cover off the wrong motor was placed in unbolted, this resulted in the drive end higher then the the brush end loosening the belt tention. i looked at the manual schematic, the motor is supposed to have a bracket attached to the top of it, two bolts come down from the top of the motor housing to attach to this bracket that built on top of the motor, no brackets, wrong motor i found the motor completely loose just the drivs pulley and the belt holding it in place. they refunded me my 700.00$ i paid for it and let me keep the unit. the ajustment knobs need to be pulled apart and cleaned. the tailstock seems to be aligned with the head stock i will not know for sure until i buy the appropriate messuring tool to check.

I bought a book ,titled the home machinist it came with a plan to build a small milling chuck and also the motor drive arrangement. i am going to focus on building simple things first before i attempt anything complicated. I do NOT know one thing about metal lathes nor do i know even how to use the thing i do not even know what the messuring points on the knobs mean. As i stated i never claimed to be a machinist, the whole argument was caused by my item on cylinder taper. I do need help and advice.

Thanks
D

 

[petertha]

I don't think leaded steel lends itself to hardening aside from case hardening compounds that add carbon via the process. At least, according to this
http://www.interlloy.com.au/our-products/bright-steels/12l14-bright-mild-steel/

When you say 'mini gear pulleys' do you mean those used for toothed belts? They are available in all kinds of configurations, typically aluminum btw. Unless you have some very custom application, or want to make one for making's sake, probably simpler & cost effective to buy one & modify as required. Also, check into the tooth form & flange, it might not be as straightforward as cutting a gear (assuming you find gear gutting straightforward LOL).

 

[D&J Fitzgerald]

Hello I thank you kindly for your reply, i want to mill grooved pulleys and use round non toothed belts the dia. of each will be 1/2, 3/4, 1 inch with a 1/8 wide tapered groove in the middle with sloted v angle on the inside so the belts grab. and mill the centre holes for the motor shafts at 1/8 or 3/16 and 1/4 .

you mentioned aluminum i did order some on ebay. i prefer light alloy steel for the pully's but if not, then carbon steel round bar. The problem with Aluminum is the cost, i typed in ebay carbon steel round bar, but SST keeps popping up.

Can you recommend a supplier in Canada or the U.S that supplies reasonably?

Also can you recommend a machinist beginners idiat book, because i need some help.

Thanks very kindly.
D

 

[petertha]

Re pulleys - I would check the likes of Ebay & Aliexpress, examples below. They call them 'circular belt pulleys'. Sometimes half the battle is figuring out the name.Again, these are aluminum which I have seen on 1 HP machines, but you may be able to find steel. You might be better off just going V belt & sheave because they are very common off the shelf items in N-Am. But I don't know your dimensional constraints.

Re materials - Canada sucks when it comes to small quantity & reasonable metal prices IMO. Our local MetalSupermarket is very expensive & limited alloy selection. But, its all about all-in costs including shipping & metal is heavy so factor that into your online shopping. Personally for my needs (diverse alloys & generally 1 foot sections) I shop from OnLine Metals & Speedy Metals from USA. Speedy only ships UPS so expect that to hurt with courier fees. OLM also ships UPS but gives a bit of price break to Canada, bless them. I've found a local re-shipper that helps facilitate cross border shipping but the difference is slim on low (say < 50$) orders because they want their fees too. Metal scrap yards are getting to be a thing of the past & the chance of you landing on a lump of 6061 is slim to none. Any machine shops are using their own stock or selling any off-cuts downstream to the likes of MetalSupermarket.

Books - easy one. Type 'machinist books' into Ebay, used book re-sellers or even Amazon but look for used. There are some excellent books that were probably $100-$200 new & sell for a fraction. Typical high school machine shop or trades books are probably your best bet. Or put a want ad in our classified section, you might find some good deals that way.

pulley examples

https://www.aliexpress.com/item/Mis...1154f11&transAbTest=ae803_1&priceBeautifyAB=0

https://www.aliexpress.com/item/CNB...aU5lhvd&transAbTest=ae803_1&priceBeautifyAB=0

 

[packrat]

Daniel try and find a copy of HOW TO RUN A LATHE BY SOUTH BEND LATHE CO. lots of information in that little book.
You can down load a copy on the net or find a hard older copy on ebay {SBL no longer prints the book}..also old high school books on machine shop and lathe work can be of help, also lots of youtube videos out there on lathe work... search McMaster-carr they have any round stock you would need..HTH

 

[petertha]

The OP (Daniel) said he lives in Canada (post #3) so unfortunately McMaster Carr may as well be on the moon for us living in Kanuckistan

 

[compressor man]

YouTube is a fantastic source for learning this stuff. If you can dream it up there is likely someone who was kind enough to have made a video teaching you how to do it.

 

[packrat]

Did not know McMaster-Carr was not shipping to Canada..when I was doing pluming and HVAC work I called in a order almost every day and had it the next morning before 10:00am, of course the big company I worked for paid the over night and or 2nd day UPS shipping cost......

 

[petertha]

That's the difference. Companies, educational facilities... they will accept accounts & justifies the customs paperwork. Common mortals = nope. Been that way for several years. Damn shame, but it is what it is.

 

[holmes_ca]

Hello I thank you kindly for your reply, i want to mill grooved pulleys and use round non toothed belts the dia. of each will be 1/2, 3/4, 1 inch with a 1/8 wide tapered groove in the middle with sloted v angle on the inside so the belts grab. and mill the centre holes for the motor shafts at 1/8 or 3/16 and 1/4 .

you mentioned aluminum i did order some on ebay. i prefer light alloy steel for the pully's but if not, then carbon steel round bar. The problem with Aluminum is the cost, i typed in ebay carbon steel round bar, but SST keeps popping up.

Can you recommend a supplier in Canada or the U.S that supplies reasonably?

Also can you recommend a machinist beginners idiat book, because i need some help.

Thanks very kindly.
D

 

[holmes_ca]

Daniel, you can try metal supermarket in Canada

Edmund