Quantcast

straight 6

Help Support HMEM:

neil_1821

Well-Known Member
Joined
Mar 5, 2015
Messages
91
Reaction score
27
thanks for the goog words its my own design
That’s even more impressive being your own design. I bet it was a huge relief when it fired up and sounded like that!

Would you ever consider making plans to sell or perhaps the 3D models? I’d suspect there would be a lot of interest from the modelling community.
 

sbdtasos

Well-Known Member
Project of the Month Winner
HMEM Supporter
Joined
Oct 29, 2011
Messages
143
Reaction score
314
Would you ever consider making plans to sell or perhaps the 3D models? I’d suspect there would be a lot of interest from the modelling community.[/QUOTE]

that is what i am doing wright now ,trying to print the parts with all dimenssions
 

Linton Evans

Member
Joined
Sep 1, 2018
Messages
5
Reaction score
2
Location
Auckland, New Zealand
Would you ever consider making plans to sell or perhaps the 3D models? I’d suspect there would be a lot of interest from the modelling community.
that is what i am doing wright now ,trying to print the parts with all dimenssions[/QUOTE]


Yes _ I too totally agree - Would you consider making the 3D files available for purchase?? Thanks
 

Willyb

Member
Joined
Jan 21, 2016
Messages
24
Reaction score
4
Congratulations on selling your motor. I was wondering if you remember what camshaft timing you used? It sounds really nice. Planing on building an engine and would like something similar for the camshaft.
Cheers
Willy
 

sbdtasos

Well-Known Member
Project of the Month Winner
HMEM Supporter
Joined
Oct 29, 2011
Messages
143
Reaction score
314
Congratulations on selling your motor. I was wondering if you remember what camshaft timing you used? It sounds really nice. Planing on building an engine and would like something similar for the camshaft.
Cheers
Willy
this is my camshaft
intake open 40btdc
intake close 30abdc
exhaust open 30bbdc
exhaust close 40atdc
cam2.png
 

gbritnell

Project of the Month Winner!!!
Project of the Month Winner
Joined
Jul 16, 2007
Messages
2,665
Reaction score
568
You're intake timing is a little radical for a model engine.
gbritnell
 

johwen

johwen
Joined
Apr 28, 2010
Messages
58
Reaction score
10
Very radical timing as it will be hard to start and difficult to get to idle and a lumpy motor. I would suggest an Overlap of 20 degrees myself
Johwen
 

leerkracht

Member
Joined
Mar 18, 2020
Messages
24
Reaction score
43
Location
Tienen B
Radical timing ?
the effective timing of the camshaft you need to measure with the clearance from 0.05mm to 0.1mm , you have a lot les timing with these small lobes (make an assembly > inventor and see the result with different clearences )
 

Attachments

Willyb

Member
Joined
Jan 21, 2016
Messages
24
Reaction score
4
this is my camshaft
intake open 40btdc
intake close 30abdc
exhaust open 30bbdc
exhaust close 40atdcView attachment 119328
Hi sbdtasos
Thank you for making this information available. What idle rpm would you reliably get using this Camshaft timing? Thanks again for the information.
Cheers
Willy
 

johwen

johwen
Joined
Apr 28, 2010
Messages
58
Reaction score
10
It would depend on flywheel weight and inlet manifolding for even fuel distribution. It wouldn't be slow and if it was would be lumpy. I would open the the exhaust 45 BBDC and close 10 ATDC and Inlet open at 15BTDC and close 30ABDC. With good porting and valve shape would give a nice running engine and a slow idle speed. Hope this helps. John from down under
 

Willyb

Member
Joined
Jan 21, 2016
Messages
24
Reaction score
4
Hi John
I should have referred to the idle speed "sbdtasos" was getting in his video of Post #29. Sorry.
In the Video, the motor seems to be idling quit slow for these Camshaft timings. I would guess between 1500 and 2000rpms?
Yes it's lumpy but that's expected. Starts very well also.
Interested in looking at the plans when available.

Thanks John and sbdtasos
 

JCSteam

Well-Known Member
Joined
Nov 30, 2016
Messages
467
Reaction score
128
This is an awesome engine. Very nice work on the machining. The Turbo is especially interesting, not many seen on small engines.

Regards
Jon
 

petertha

Well-Known Member
HMEM Supporter
Joined
Jun 24, 2010
Messages
1,492
Reaction score
281
...the effective timing of the camshaft you need to measure with the clearance from 0.05mm to 0.1mm , you have a lot les timing with these small lobes (make an assembly > inventor and see the result with different clearences )
Hi leerkracht. I dont want to digress this post about cam design. I think I will make a new post on that subject because I have more questions. But your comment caught my eye as I was just looking at this same aspect myself. Just to use this cam as an example, is this an appropriate method to determine 'true' cam timing considering clearance as you mention?

I took his drawing & replicated myself. It shows 156.2 deg of valve open duration just based on the cam geometry. But that is only theoretical, no clearance. If I draw a peripheral clearance circle of 0.10 mm around the center & look for the new intersection, it reduces the open duration to 126.4 deg. I have made myself a spreadsheet to evaluate cam timing for model engines and to use the plot visualization, I think what happens is the reduced duration due to clearance effect acts like the black arrows (shortens the bars). So overlap is also affected. I know this is simplistic because other geometry issues enter the picture. But I think I see what you are saying, a small amount of clearance has a magnified effect on small model cam profile.
 

Attachments

johwen

johwen
Joined
Apr 28, 2010
Messages
58
Reaction score
10
If you listen to the V/12, a lovely engine, at idle it is not smooth but it smooths out when the revs rise and i guess it needs the power at at high revs. Also it is turbo'ed. You can change the power curve by changing valve timing. But the first decision is what will the engine be used for i.e. if you want a smooth running engine at low speed the timing is best set mildly on the other hand if it is a racing motor then more radical timing is the way to go. Exhaust systems and inlet systems will also vary the power/torque curves John. from down under.
 

leerkracht

Member
Joined
Mar 18, 2020
Messages
24
Reaction score
43
Location
Tienen B
the v12 of 180 ° runs uneven on idle because it was the first run of this engine , so completely new and not yet properly settings of the carburator and run in , now this engine runs very smoothly over the entire rev range.800-3600 rpm under load of the 4 bladed prop wiht a 3 blade or 2 blade prop easyly rise the rpm over 4000

pictures of coversion the v12 60° from 3 single Super Tigre carburators to 6 double home made immediately 500 rpm more

enjoy
 

Attachments

Latest posts

Top