Author Topic: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine  (Read 129372 times)

Offline joncarruthers

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #180 on: December 05, 2015, 09:01:32 AM »
Thank you Jim, this is a completely new area for me, fascinating.

Do you find any advantage tuning the carb bell mouth length?

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #181 on: December 05, 2015, 05:29:05 PM »
Thank you Jim, this is a completely new area for me, fascinating.

Do you find any advantage tuning the carb bell mouth length?

Google, Best Bell-Prof. Blair & Associates. Click on related articles. This pdf. is what I used for the design of my carburetor bell mouths. Also found here; File:(Blair and Cahoon) Design of an intake bellmouth Sept , under file history click on date/time.

JA
« Last Edit: December 05, 2015, 05:34:07 PM by strictlybusiness1 »

Offline petertha

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #182 on: December 21, 2015, 07:41:51 PM »
Hi Jim, I wanted to inquire about one of your earlier replies. From the pics, I didn't really get the sense you were continuously flooding the part with oil (you mentioned 'basin') or maybe I misunderstood. Is it sufficient to pre-drip some oil in the bore to assist with grinding, or did I miss the detail here? What is significant about previously used oil vs. new oil?  Is there any consideration to the lathe rpm, or basically as long as its moving & correct counter-grinder direction? (ie. higher lathe rpm more/less prone to vibration?). What about X-travel rates, is slower better or just whatever cuts best with a particular grit? I'm amazed at the mirror finish of #100, is that about as fine as you go for chrome?

1/2" or 3/4" wide, 100 grit aluminum oxide wheels which are dressed round after mounting. The size of the dressed wheels are approximately 1.000" to 1.100". I use a sulfur based grinding oil, Sunnen #MB 30-5, which has been used to previously grind chrome. In the photo notice that the lathes bed is completely covered. The oil is caught in a basin below the lathe's bed to be used again & again & again. Never use new grinding oil to finish grind hard industrial chrome.

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #183 on: December 22, 2015, 10:27:25 PM »
Petertha,

When grinding hard industrial chrome, I'm continuously flooding the part. I catch this sulfur based grinding oil (Sunnen # MB 30-5) in a basin beneath the lathes bed & DO NOT allow it to get into the oil based lathe coolant. I have not tested what will happen when only a small amount of oil is placed in the bore before grinding. Sunnen advised that the oil used to grind chrome should be used again & again. They said the finish would improve with continued reuse. I always rotate the part as slow as possible in a direction which is opposite to the grinder's spindle. Lathe RPM's of 50 to 70 & grinder spindle RPM's of 20,000 to 26,000 work the best on the 1.125" bore. Always use the largest diameter stone possible in a particular bore. Vibration problems can come from bad bearings in the grinder's or lathe's spindle, the grinders motor, a part that is not rigidly mounted or a tool post grinder that is not rigidly mounted. Always feed the X-travel at the slowest rate possible so that no heat will be generated in the part. Always feed completely through the bore before reversing directions. Sometimes after putting on to much chrome a 60 grit wheel is used for roughing. Finish is still done with the 100 grit stone.

This process is similar to what is done on the Sunnen honing machine except the cylinder is held by hand. It is stroked in & out as the single stone mandrel is rotating. Rotational speed is approximately 400 RPM & the stones used are from 280 to 400 grit. The stone in the mandrel is under pressure which is applied with a foot pedal as the mandrel is rotated. The same type honing oil is used & the finish is comparable to the 100 grit ground finish.

Jim Allen

Offline petertha

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #184 on: January 31, 2016, 07:11:42 PM »
Hi Jim. I'm looking at some of your lathe bed wheel dressing fixture pictures. Does your work routine go:
- initially dress the wheel with lathe bed fixture in place
- remove dressing fixture altogether, do the part grinding operation
- if grinding wheel requires touch up before part is done, remount the dressing tool & (somehow?) re-register the bore dimensions where you left off
Or maybe I have it wrong & this fixture stays in place during the entire operation? That way you can re-dress at any stage so re-establishes same datum but with a fresh wheel surface so to speak. (Hope my clumsy wording is making sense).

In another pic, you mounted a dressing tool in the chuck. Is this an example of a 'one-type' wheel tune up where maybe you don't have the room to mount the lathe bed dresser?
In this case, do you somehow brake the chuck to prevent the dressing point from rotating (=wheel diameter variation)

-Peter

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #185 on: February 01, 2016, 08:06:43 AM »
Hi Peter,

The top photo is not a lathe bed. It is the bed of my OD-ID grinder. Look behind the tapered arbor & you can see the OD grinding wheel. I dress either the ID wheel or the OD wheel, remove the dresser & then grind. If the grinding wheel needs to be re-dressed in either case, I remount the dresser. I can easily return to the original position of either wheel because there is a .000050" indicator mounted on the cross feed. The same procedure is done on the lathe shown in the second photo after the spindle is locked.I may have some photos of both machines with their mounted indicators.

Jim Allen

Offline petertha

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #186 on: February 02, 2016, 02:16:28 AM »
The top photo is not a lathe bed. It is the bed of my OD-ID grinder. Look behind the tapered arbor & you can see the OD grinding wheel.

Aha, that explains it. I thought maybe it was the Themac installed on a different, prior lathe. And yes, now I see the big OD wheel.
Now I get the L-bracket & your dial indicator setup too. OK, the fog is slowly lifting.
In one of you prior pics you showed a DTI set against the compound & a comment to the effect of nil needle movement during grinding. But now I suspect that wasn't for feed measurement, that was validating 'stability' during running?
(I'll gladly try to absorb any other pics you have, meanwhile thanks for your patience in explaining).

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #187 on: February 02, 2016, 04:33:28 AM »
Peter,

The Themac is used on both the lathe & the OD-ID grinder. I made a special drop down mount so that I can use it on the OD-ID grinder. The reason for doing this is because the ID grinding attachment that comes with the OD grinder has a low spindle speed. The Themac model J-45 with its flat belts & pulleys can operate from 4200 to 42,000 RPM. The small holes that I grind internally use a spindle speed of 26,000  RPM. I do use the .000050" indicator for precise feed measurement & to tell me exactly where the compound or in-feed position is at all time

Jim
« Last Edit: February 03, 2016, 11:39:04 AM by strictlybusiness1 »

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #188 on: February 03, 2016, 11:42:00 AM »
Peter,

I will ad to my explanation. I will use several different sizes of no-go, go, gauge pins, when grinding ID holes. I have found this method of measuring to be easier & more accurate than using bore type gauges. For example, a .2500" ID hole is ground in steps starting at .2480". Each gauge pin used will be .0001" smaller than the desired size. Therefore, a .2499" pin will fit snugly into a .2500" hole; a .2479" pin will fit snugly into a .2480" hole. Once you have picked up a size, grinding in steps of the same amount gets the hole to size within + or - .0001". With some practice the process is easy to do.

Jim Allen

Offline petertha

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #189 on: March 03, 2016, 03:43:24 AM »
Hi Jim. More ID grinding questions. (I hope you are not sick of me yet  :D).

- when you dress your wheels that are in the smallish diameter range (say sub 1" OD), do you reduce rpm back on the tool post grinder to lowest pulley setup in this mode? ie. something less than what metal grinding mode itself would be? If so, is there an rpm rule of thumb for safety?

- prior to ID grinding, do you set the axis of the grinder spindle at some slight angle relative to axis of work so it cuts with kind of a leading edge effect? Or is the grinder spindle parallel with lathe rotation axis. It was suggested to me that a wider ID wheel and/or parallel running requires some HP on the part of grinder motor. But that Themac model looks pretty beefy.

Offline petertha

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #190 on: March 03, 2016, 05:44:01 AM »
Hmmm.. going back through the pics maybe I have insight into Q#2 looking at one of your setups if I interpret it correct. You have the tailstock set in the pulley end of the spindle. Assume its zero-zero alignment insurance & maybe helps with vibrations? A lot of details to this grinding business for sure.

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #191 on: March 05, 2016, 09:55:21 AM »
Hi Peter,

Sorry to take so long to answer. I'm still working on completing the set up of the new shop. I dress the wheels at the speed they will be operated at when grinding. For example, 1/8" to 1/4" wheel diameters are run at 42,000 RPM; 3/8" to 5/8" at 31,000 RPM; 3/4" to 1" at 26,000 RPM; 11/8" to 2" at 9,300 RPM; 21/8" to 4 " at 6,300 RPM; 41/8" to 5" at 4,200 RPM.

I do not set the grinder spindle's axis at an angle to the carriage's axis, because the grinding wheel will be dressed using the carriage's axis. Truing is necessary so that the wheel will be concentric with the spindle's axis. A wheel which is out of round or not concentric will pound the work piece, wear fast & produce poor finishes.

JA

Offline petertha

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #192 on: March 05, 2016, 06:58:38 PM »
Thanks Jim. Good luck with ongoing shop completion.
I PM'd you when you have some time.

Offline strictlybusiness1

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #193 on: November 25, 2016, 08:34:29 PM »
I have completed the setup of both shops used for engine building. The photos show some of the tooling used for finished chromed aluminum cylinders. The chroming process has been developed to give a very high quality cylinder wall with .00005" roundness. More to come on this process.

Jim Allen

Offline Admiral_dk

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Re: .90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine
« Reply #194 on: November 25, 2016, 09:54:15 PM »
Glad to see you back Jim and will be looking forward to more education from you  :praise2:

Best wishes

Per

 

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