Start to Finish: Building Our 50' Skater
#1481
Registered
overdrivebox look nice! Are there any space above the box? Another layshaft would reduse bearing and teeth stress to half. Weight are not double because gears and layshaft could be lighter. Then there will be zero radial forces at input and output shafts and loading come two teeth simultaneous. Roller bearing and straigh cut gears does not have much power loss. I think biggest powerloss and heating will come from oil viscosity. Oil is pressed between teeths so it warms up like hydraulic motors etc. dry sumping only reduce heat, but make it more complicated. Nice work, keep going! You inspire me continue my own fast diesel project.
There would be more power draw from the second idler gears set and more heat generated. And we may not need it, but would not know till we try with out it.
The cases are easy for me to make so if we break a set of gears I will just make new cases that do have a second idler shaft and still be able to use all the same shafts and gears.
#1482
Registered
VIP Member
Join Date: Mar 2016
Location: Stephenville
Posts: 331
Likes: 0
Received 0 Likes
on
0 Posts
I’m sure you have the machining abilities for it, but if not, my brother works in oilfield manufacturing. More specifically fluid ends, turntables, draw works etc. Heavy duty, full load, custom gears are made all the time in house.
#1485
Registered
Join Date: Apr 2013
Location: Lake Winnebago
Posts: 203
Likes: 0
Received 0 Likes
on
0 Posts
Instead of getting your overdrive ratio from a compounded spur gear set......how about an inline planetary?.... 4000 series allison transmission planetaries (or similar) should have the torque capacity and longevity you are looking for...they would also fit into a smaller envelope...integrate them into your own case ( i realize that would be a complete redesign for you).
the main issue would be ratio selection...unless you make your own.
the main issue would be ratio selection...unless you make your own.
#1486
Registered
I have been trying to find a Mercury M8 lower that is broke or taken apart so we could look and measure to see if it would be possible to change the lower ratio. That would keep me from having to add the overdrive box, weight, power loss, ect.
The lower ratio is a 22 tooth driving a 25 tooth. Which is a 1.14 ratio under drive. If I could switch the gear tooth count to 25 driving a 22 it would give me a lower ratio of .88 and an overall ratio of .85 over drive which would be about where I want to be. If we could have gears made and possibly cut the side of case and put a plate over the hole I think it would work and not really cause much drag once were going. It would be the top of the bullet which is out of the water when were running.
Does anyone have a M8 Lower that is broken or taken apart for any reason that I could borrow to measure? I do not want to take mine apart because the engines will be done next week to test the boat. And they are still factory set up which might give them a better chance of living then if I take them apart and put back together.
#1487
Registered
Join Date: Apr 2013
Location: Lake Winnebago
Posts: 203
Likes: 0
Received 0 Likes
on
0 Posts
Also...for gear box testing purposes you could build a 4 square it allows two boxes to be tested at the same time and at varying levels of torque (whatever profile that is deem necessary) ..... Ive life tested transfer cases in as little as a couple weeks with one.
#1488
Registered
I have egt probes on each cylinder, I'm using a guage for aircraft that has 12 inputs. it is not water proof and the last time I ran it I had just put it in and used clear tape over it to keep water out since it was raining. I just finished the cover for it yesterday. The pics are upside down, I will fix them when I get to a hotel tonight.
Last edited by BigSilverCat; 12-30-2017 at 12:40 PM.
#1489
Registered
Tyson - a bit of advice and maybe you are doing it already but you should monitor exhaust manifold pressure (not back pressure but between exhaust ports and turbo) and that should be right along side boost pressure, you know boost has to be higher than exhaust, when it is not the engine can't breath anymore and things melt - again not an expert just years of looking over damage.
#1490
Registered
Tyson - a bit of advice and maybe you are doing it already but you should monitor exhaust manifold pressure (not back pressure but between exhaust ports and turbo) and that should be right along side boost pressure, you know boost has to be higher than exhaust, when it is not the engine can't breath anymore and things melt - again not an expert just years of looking over damage.