Author Topic: Help me finding the timing!!  (Read 1194 times)

Offline glorfindel

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Re: Help me finding the timing!!
« Reply #15 on: January 17, 2021, 06:18:25 PM »


I'll be watching along glorfindel. I'm just starting the same cad exercise myself.... and not trying to get too distracted from my radial build.

- what is your rationale for changing the bore slightly from nominal metric to nominal imperial units by the little amount? Aren't the rings going to be sized based on resultant bore whatever it is (Trimble method), or do you have some other method in mind?

- what features of the Edwards pushrod system are different or better than this design in your opinion?

- not sure if you saw my inquiry post here on the forum about the Hirth coupling, but just wondering if you plan to adopt that feature on the crankshaft or have something else in mind.

I already have a 1-3/8 reamer ;-). I dont like how he make the rings. He seems to make an over sized ring... I will use my own piston design, with 2  0.050" square rings, and my own conrod design with bronzeBushing instead of a needle bearing.

I'm not fixed on the pushrod system yet...I will work on it today and post some updates.



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I did a search on Hirth coupling, but i ddint see your post. can you link me to it

Offline petertha

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Offline glorfindel

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Re: Help me finding the timing!!
« Reply #17 on: January 17, 2021, 08:17:21 PM »
Is there a reason to not put the pushrods straight???

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Offline Charles Lamont

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Re: Help me finding the timing!!
« Reply #18 on: January 18, 2021, 09:20:31 AM »
I can't see any need for the push-rods to be angled. As far as I can see, the cam box could be altered so that the cams could be spaced to allow the push-rods to be square. On the other hand angled rods are not uncommon and that slight angle is not likely to be a problem, except that it will eventually cause the tappet holes to wear oval.

I don't like the skinny little tappets either. Are they supposed to have a slightly domed end, or are they flat?

Offline glorfindel

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Re: Help me finding the timing!!
« Reply #19 on: January 18, 2021, 06:41:20 PM »
I can't see any need for the push-rods to be angled. As far as I can see, the cam box could be altered so that the cams could be spaced to allow the push-rods to be square. On the other hand angled rods are not uncommon and that slight angle is not likely to be a problem, except that it will eventually cause the tappet holes to wear oval.

I don't like the skinny little tappets either. Are they supposed to have a slightly domed end, or are they flat?
There is a radius. Pushrods are small too (2mm), but it should be ok, they will be made from drill rod.

Here i am so far. I got some minors interferences, but i'll sort it out soon.



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Offline petertha

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Re: Help me finding the timing!!
« Reply #20 on: January 19, 2021, 02:01:30 AM »
I haven't modeled it as far as you but I tend to agree, why not align the pushrods straight & adjust the cam lobe spacing accordingly. There appears to be room to extend the cam box housing & end bearings fore & aft to accommodate. I was also wondering to myself if maybe the rockers might be sitting at in a bit different position along the axle, but the general assembly shows as you have it - right adjacent to the upright supports. Sometimes things become more apparent as you get deeper into the design. And sometimes they don't haha.

Offline glorfindel

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Re: Help me finding the timing!!
« Reply #21 on: January 19, 2021, 11:57:24 AM »
I haven't modeled it as far as you but I tend to agree, why not align the pushrods straight & adjust the cam lobe spacing accordingly. There appears to be room to extend the cam box housing & end bearings fore & aft to accommodate. I was also wondering to myself if maybe the rockers might be sitting at in a bit different position along the axle, but the general assembly shows as you have it - right adjacent to the upright supports. Sometimes things become more apparent as you get deeper into the design. And sometimes they don't haha.
The design is a little more compact with angled rods.

I still dont know what to do with the coupling.... I can use a graving tool to do the hirth coupling.

Do you have some pics of the "Schiling" way to do it ???

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Offline glorfindel

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Re: Help me finding the timing!!
« Reply #22 on: January 19, 2021, 02:56:28 PM »
Did some test with 60 deg graving tool and the link you provided for hirth calculation.

Looks good.

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Offline petertha

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Re: Help me finding the timing!!
« Reply #23 on: January 19, 2021, 07:48:21 PM »
I still dont know what to do with the coupling.... I can use a graving tool to do the hirth coupling.
Do you have some pics of the "Schiling" way to do it ???

go to post reply #14, there is a link to PDFs
https://www.modelenginemaker.com/index.php/topic,10107.0.html

His methods seem to vary by engine design, but from what I can see, various combinations of crank pin & axial retention bolt. Mike (Vixen) made a good point in the Hirth discussion that just joining the crank ends may not be sufficient. If I understood correctly, potentially the crankshaft assembly would be joined up but joint journals left oversize to be finish OD ground as a mated pair? Here I'm on uncharted waters. In some cases the pin OD surface is a sliding fit against say a bronze bushing of a connecting rod. In other cases they would be a presumably tighter fit to the ID of a hardened bearing inner race. Ohrndorf has (an even longer) V12 with built-up crankshaft, I'm going to look at that in more detail now. I think part of the design success depends on layout, spacing & accuracy of supporting bearings to minimize CS flex in any direction, but its just a hunch.
« Last Edit: January 19, 2021, 07:55:36 PM by petertha »

Offline petertha

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Re: Help me finding the timing!!
« Reply #24 on: January 26, 2021, 03:57:44 AM »
Re crank joining, there are 2 more references to ponder

A Bugatti on this forum (journal press fit into hole if I understand)
https://www.modelenginemaker.com/index.php/topic,6848.45.html

And coincidentally another Bugatti on the other forum (4 index pins & face to face joint if I understand)
https://www.homemodelenginemachinist.com/threads/bugatti-straight-8-cylinder-with-blower-design-3d-printed-molds-castings-machining-assembly.32045/page-3

The assembly & post finishing seems to be where the magic happens.

I'm sure I've seen more examples, I just never thought to bookmark them.

Offline glorfindel

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Re: Help me finding the timing!!
« Reply #25 on: February 23, 2021, 02:14:43 PM »
Coupling stuff was annoying me, so i did a flat twin lol!!!

I'll start fabricate it in 2 weeks!!!



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