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1947 Jepson engine

machining main bearings

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geoff walker 117/09/2017 14:03:07
409 forum posts
159 photos

20170917_123053.jpgHi All,

The photos shows one of two part machined main bearings for my jepson engine.

It is 5/8" dia cast bronze in two halves, soft soldered together. It has been waisted and the two holes are 8ba clearance.

I need to cross drill/bore a hole around 6.1mm diameter on the join line. The hole has to be parallel to the underside and also square to a centre line through the two holes. The hole position on each bearing has of course got be exactly the same.

I'm struggling with a 4jaw or face plate set which will give me the accuracy I need.

Any ideas anyone? the two outer faces will be machined later using a small expanding stub mandrel.20170917_123113.jpg

cheers geoff

JasonB17/09/2017 14:08:08
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Pop it in a vice and either mount that to a vertical slide or on the mill table if you have one, not only will it make it easier to position the hole but will stop the part bursting open as you drill and I assume ream to 1/4"

May have been better to do the hole first and then shape the part as you would have more material to hold.

Edited By JasonB on 17/09/2017 14:09:19

JasonB17/09/2017 14:15:34
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Just looked at the drawings, I'm not sure you will be able to get the full length of the 7/16" dia out of it.

 

I'd probably do it with two rectangles 5/8 x 1/2 stacked one on top of the other, drill, bore and ream hole and do the longer 7/16 dia at one go in teh 4 jaw. reverse and do the other 7/16" dia. Then drill small holes followed by the two scallops milled out and then just round over the outside with a file.

Edited By JasonB on 17/09/2017 14:16:43

Edited By JasonB on 17/09/2017 14:22:40

geoff walker 117/09/2017 14:32:38
409 forum posts
159 photos

Hi Jason,

Thanks, I may well have to go with a vertical slide and in my case angle plate set up.

Would prefer a to do it the other way so I can cut the oil groove in the same setting but as things stand now your suggestion looks the best way forward.

Yes the 7/16" dia will be tight, possibly slightly under but as it's not critical not really a problem. (Both my bearings will have a face width of 3/8"

cheers geoff

geoff walker 117/09/2017 17:02:46
409 forum posts
159 photos

Hi Jason

I misread your post earlier. Yes you're right I wouldn't get the full face width of 7/16".

The waist diameter is 7/16" so is good only for 3/16" each side of the centre line giving a 3/8" face width.

As you have looked at the drawing could I ask the following. The two crank webs are a full circle and quite heavy. Is that because they double up as a webs and a flywheel with the two 5/16" holes making the "web" lighter on one side.

Will post some pics of the finished bearings later in the week.

geoff

JasonB17/09/2017 17:23:16
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That looks like what is intended, the thick webs will have a flywheel effect and the two holes in each are to aid balance.

geoff walker 114/11/2017 09:18:43
409 forum posts
159 photos

Hi All.

Is there anyone out there ever made this engine, or knows anyone who has?

I have had a good look on the internet and can't find an example anywhere, so it looks like I may be ploughing a lone furrow!!!

The engine first featured in M.E. magazine back in April 1947 as a 2 1/2 page article. That article is now on the John-Tom website. In an earlier post in this thread Jason has given a link to the article.

It is the first steam engine I have ever built and probably not the best choice as I've had problems. I would not recommend this engine as a first build. Having said that I am "getting there", slowly and gradually more surely. The drawings in the article are good but not 100% correct so beware if you are to attempt this engine. I am currently CAD the whole engine as I go along hopefully correcting any issues with the drawings.

The photo shows the engine assembled with the main components, which with good running fits turns over nicely.

I'm not looking for specific help at this stage but I will be in due course, probably when I have to set up the as yet unmade valve gear.

Back to the original question. has anyone ever made this engine?

geoff ............ and yes I will be changing the screws to hex heads!!!20171114_083900 (2).jpg

JasonB14/11/2017 16:12:24
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It's coming along well Geoff. If you have them it may be worth looking at the old MEs for the months following when the engine was first published as there may be some comments in smoke rings about it.

I've not seen one made or heard mention of it until you started posting.

J

geoff walker 115/11/2017 15:14:11
409 forum posts
159 photos

Hi Jason,

Thank you and also thanks for the tip, good point.

More pics of progress in due course.

geoff

geoff walker 123/11/2017 11:47:59
409 forum posts
159 photos

Hi Gents,

A question if I may on the slide valve for this engine.

The last photo in this thread shows the ports in the cylinder block.

The outer dimension across the two inlet ports is 1/2". The ports are 3/32" wide so the inner dimension is 5/16".

From what I have read (M.E. tyro articles by W J Hughes issue 2666 and 2670) the length of the cavity in the slide valve should be the same as the inner dimension (5/16". This would seem to me to be fundamental as with the side valve in a mid position both the inlet ports will be closed. If the slide valve cavity is any longer then both inlet ports will be open with the valve in the mid position, even if only by a small amount.

The drawings for the slide valve on this engine show a cavity length of 3/8". Is this fundamentally wrong, does the length have to be 5/16" or am I missing something?

If you are a "Tyro" like me gents I can recommend the articles by Mr Hughes which also explain clearly the principles of lap, lead, angle of advance etc.

cheers geoff

geoff walker 118/12/2017 11:15:01
409 forum posts
159 photos

With tongue in cheek may I ask, do the moderators of this site have a duty of care to other users?

I speak mainly for old gits like myself. When I started this engine nobody informed me that I would have to make tiny components like these which with failing eyesight and increasingly creaky finger joints has at times been a somewhat onerous task. Hmmmm.

Having said that I'm getting there. The potts set up has been "just the job" for these mini parts.

I'm planning a first test run (air test) on Christmas day as a present to myself. I shall slip away away from the festivities to the haven of the modelling room probably with my young grandson Matty in close attendance.

Speaking of Christmas could I offer my best wishes to everyone all over the world, hope you all have a good 'un with family and friends.

Must confess I still enjoy having the tribe visit, everybody around the big table, party hats donned. The mind is forever young even if the eyesight and joints 'aint. Geoff

20171218_093141.jpg

20171218_093536.jpg

JasonB18/12/2017 11:24:55
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You had started so we thought you should be allowed to finish. However had you asked before....................

Good to see you are making progress with an end in sight, maybe a video of the running engine for us all to enjoy on boxing day could be posted if you are able, I'm sure your grandson could help with that aspect if not.

I've not seen a spindle used like that they are mostly shown cutting work held in the lathe chuck but set up like that you really just have a small milling machinesmiley

Neil Wyatt18/12/2017 20:44:11
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Posted by geoff walker 1 on 18/12/2017 11:15:01:

With tongue in cheek may I ask, do the moderators of this site have a duty of care to other users?

I speak mainly for old gits like myself. When I started this engine nobody informed me that I would have to make tiny components like these which with failing eyesight and increasingly creaky finger joints has at times been a somewhat onerous task. Hmmmm.

Fie!

This website helps prolong your active life and protect you against the ravages of senility... the more difficult we make the tasks for you the better!

Anyway, it's about time you did something WITH that Drummond instead of TO it

Neil

geoff walker 119/12/2017 17:52:39
409 forum posts
159 photos

Neil,

A fair point.

When I bought my Myford/drummond M type I spent 6 years doing nothing except renovate and make parts/accessories for it plus two other drummond M's a flatbed drummond and ......... a super adept ( now you didn't know that did you?).

This year I decided it was time to make something, the whittaker firefly 46 and now my second the jepson engine which is nearing completion. I now consider myself to be a model engineer but still a tyro.

I had the jepson running today and I'm pleased to say it ran very well. The only problem is keeping it going for an extended period. I ran it off the airbrush compressor which is fine for a small oscillator but the jepson gulps in air like a drowning man rising out of the sea. 15 seconds and the pressure has dropped and the tank has drained. I need a bigger compressor!

geoff

Neil Wyatt19/12/2017 19:17:15
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> I need a bigger compressor!

Next project identified!

smiley

Neil

not done it yet19/12/2017 19:28:56
4630 forum posts
16 photos

I need a bigger compressor!

Maybe, in the interim (for model testing) you might consider adfing an extra receiver... or two. That, or up the PRV/pressure switch to get a small increase in free air, if the motor will provide enough grunt!

For a low pressure air brush setup, a couple of coke bottles might do it? Longer to regain any pressure, mind.smiley

Ian S C20/12/2017 13:48:56
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7468 forum posts
230 photos

Geoff, you better get your self on the "Adept & Super Adept" register that Neil started a while back.

Ian S C

geoff walker 121/12/2017 13:31:04
409 forum posts
159 photos

Hi Ian and ndiy,

Thanks for your comments.

Sold the adept Ian, big mistake, I now have small indoor model room where I do much of my assembly work. The adept would have been perfect in there ideal for some "little bits".

The jepson is now on youtube, not complete, an early test run which went quite well. It's leaking here and there and needs a bigger compressor than the airbrush one being used. If I could keep the pressure up this engine would be a real high speed "fizzer"

You tube "1947 jepson vertical marine steam engine". Sorry not worked out how to upload videos, I'm rather hoping Jason or Neil will do the honours and add it to this post.

cheers geoff

Edited By JasonB on 21/12/2017 13:36:26

Jim Nic21/12/2017 14:23:27
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244 forum posts
149 photos

A good little runner, well done Geoff.

A word of caution. I found that when I used 3 in 1 oil in my engine bearings it turned gummy after a couple of months of not running. I cleaned it out to restore free movement and now use 10W30 car oil. 3 in 1's effect on O ring piston seals was even worse. sad

Jim

geoff walker 130/04/2018 16:43:27
409 forum posts
159 photos

20180429_154444.jpg29042018.jpgHi All,

Took a day of today from usual activities to prepare the Jepson engine for steaming.

Added the home made displacement lubricator to the valve chest, then the three oil cups.

The oil cups hold oil to lubricate all the external moving parts. the two main bearing ones also lubricate the big end and the eccentric via oil channels in the crankshaft. The other one carries oil via a down pipe to the cross and the small end.

Bought the cups on ebay, "cheap as chips", £1.50 for 10, why bother making them!!

Also added an additional flywheel. The engine runs fine with the combined flywheels/crank but better with the added flywheel.

I bought some PTFE sheet to make gaskets. Really impressed, only .004" thick and very easy to cut and shape with a sharp modelling knife and gives a perfect seal.

It would appear to me that I have an internet world exclusive on this engine. I've searched and can't find a single example, apart from mine of course.

Best to all Geoff

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