Topic: Rookie Build - Gilson

[Wheelhorseracer]

It is used to remove the Ackerman effect in the steering..

It is easy to put a bar across the front.. like I said before.. if they share the same arc.. you will have scrub...a scrub will exaggerate any push you have in the chassis.. also a scrub can not be tuned out with air pressure..

Here is some reading material with visuals to help...

Ackerman

Now remember that on a rear steering you need to separate the rod ends at the middle.. on a front steer you need the rod ends to be on top of each other. The drawing in the article was to show the different arcs needed to correct the Ackerman..

[Running on Empty]

Wheelhorse racer, Thanks for the info on ackerman.  I am not sure what I am going to do with my front end yet.

Placed an order with EC today. 
I ordered...

rear hubs
rear sprocket hubs
rear sprocket
tranny quick change hub
tranny sprocket
king pin spacers
tranny plate bushing
split collars
and a MCP brake set-up

Also ordered 8" rear wheels but they were on back order.  Was going to order tires, but what good are tires if I dont have rims????

I decided I am going to go with pillow blocks in the rear end to hold the axle.  So the Metal addition to the rear end you see in the previous pics, will be coming off.  I will build a support for the pillow blocks to set on out of 1" square tubing, and weld it into the frame and reinforcement structure.  I think using pillow blocks will be stronger than flange bearings in my case, and it will also provide me with ride height adjustability by placing spacers between the frame and the pillow blocks.  Yea, it will not be as easy to adjust as the adjustable cassettes, but I am OK with that.
I need a little help getting the right sprocket/pully combinations to start out with. 

I will be runing a 16 Hp opposed, 700 tranny, and 16 inch rear tires.  I planned on starting out with an 8" pully on the engine, 5" on the tranny, 12 tooth sprocket on the tranny, and 48 tooth sprocket on the axle.  Am I even in the ball park for where I should be?

[lowgalaxie]

Sounds pretty close on the gearing. I run 6.5 on motor 4 on tranny 17 on output and 48 on axle.

[mowpower]

Doing the math that put you at 7.5:1

[Running on Empty]

Fabricated the pillow block mounts for the rear end tonight and welded them into the frame.  I think this will work out well.  I will weld some supports going the width of the frame once I have the axle and the sprocket mounted so I can see the clearance I will need.  I will square up the rear of the frame and box it in with some 1/8" plate.

[Running on Empty]

Mowpower, how did you come up with that ratio?  I didint get that when I figured it out.  Maybe I did something wrong.  I came up with 6.4:1.

[mowpower]

Take the trans pulley and divide it into engine pulley= belt ratio   
Take axle sprocket and divide it into the tran sprocket= axle ratio
I used a trans gear as 3:1 That is what a 700 has in 3rd gear. Both gears are 25 and your trans input is 3:1 the..   So it looks like this Belt ratio X axle ratio X trans gear ratio 3   Here is mine 6in on engine 3.5in on trans. Equals .583   12T on trans 48T on axle equals 4.00:1    So take .583 X 4.00 X 3.00 equals 6.99:1 as final drive ratio. Now this is what I do. I carrier a 13T sprocket also. Just by changing the trans sprocket to 13 from 12 my final gear changes to 6.45:1 With EC quick change setup and there idler adjustment sprocket I don't have to replace the chain when I change between the 2 I can change the front sprocket in 15 mins.I just recheck your numbers and I still come up with 7.5:1 your belt ratio should be .625 your axle ratio is tha same as mine 4:1. The only thing it can be is you used a different trans ratio then I did. I would say that most of them use 3:1 as the trans ratio. Because you are over driving or under driving the trans mission gears. Yes you are overdriving the transmission input

[Wheelhorseracer]

That is the same set up I run.. the only issue you will find is that the pillow bearing is able to move in the housing... so if you axle flexes, the bearing will just move with the axle.. I have had my axle flex in the middle and you could see it rub on the cross tube I built in.. when the axle flexes enough that it will become a permanent bend. Every bent axle I had this year, bent in the middle between the axles.

I would suggest one more pillow bearing in the middle to eliminate the flex in the middle of the axle. It's more weight, but will minimize the chance of bending an axle in the middle, or a stronger tube slipped over the axle to help minimize the flex.

[Running on Empty]

Mowpower,

Yea I used a different ratio for the tranny.  Thanks for correcting me.  I picked up the wuick change hub from EC.  I was thinking of doing exactly what you were talking about by being able to change the tranny sprockets without changing the chain.

Thanks again...Wheelhorseracer,

Are you runing a 1.25 axle?  I was thinking about putting another pillow block in the center, but the frame is not that wide, so I was unsure about the axle flex.  It can be added easy enough.

Will I have a problem getting through tech if I use 1/8" plate to box in the rear of the frame as opposed to the origional piece?  The origional piece will interfere with the bearing support tubes I welded in, plus it is a heavy stamped piece of 1/4" steel.  I think the frame would be stronger the way I want to do it.

[Wheelhorseracer]

I'm running a 1" axle.. I should have used a 1 1/4 chrome moly axle and I bet i wouldn't of had one problem...

It gets expensive when you bend axles on bumpy tracks...

[mowpower]

That my friend is a close call. That would kinda of be up to the tech guys. I do tech for ARMA and our local region. Althrough ARMA did kinda of bend the rules abit about replacement sheet metal. I would go to ARMA web www.golawnmowerracing.com and post that on the build section. Maybe you could get Larry or George to answer that. I was at the national meet in Salisbury this past weekend. Larry and I had a long talk about some of the rules during the rain. Now if I were to tech it as long as it looks like it belongs there I wouldn't see a problem with it. That is just me. Not to bring there stuff to this fourm. Last week I ask about putting a Midget seat on my mower. It was a low profile alum seat with rib supports. You will find it in the build section. It was kinda of shot down about they wanted it to look like a mower. I'm going to compair apples and oranges here. I have a MTD and there is noting under the frame for support. Well were the mower deck had a pivot point in the frame I ran a 1" square tube across and bolted it to the frame. It really stiffen the frame in front of the rear wheels. There was nothing from the rear axle to the front frame cross member. I was question about it at the race. We are not allowed to tech our own mowers. I could use it, But it did bring up a question of what it was.

[Running on Empty]

If worst comes to worst, I can just weld the origional rear panel to the 1" square tube and be done with it.  I cannot bolt it back in because the bolt holes are covered up with the square tubing.  I think it would be a lot stronger the way I want to do it. 

[Running on Empty]

I will weld the origional rear plate in, then there will be no question.  I just realized that I need to move the pillow blocks back to maintain the origional centerline of the rear axle.  I dont know why I didnt realize this until now!!!!!!!  I have some ideas as to how I am going to do this and still be able to bolt the pillow blocks in place.

[LVine2001]

Dude, your building a Gilson !!!

I am the proud owner of the Gilson Don Gienger on the G-Team website.

It looks like you have the same frame there but I am a bit confused.

If you are building a prepared type chassis or Mod-X you are going to want to lower that thing as in, move the axle up into the frame not add to the bottom. What you are doing is putting it back more to stock ride height.
 I run 16 inch tires and it sits just right with the axle up into the frame...
Take a look... http://www.g-team.us/DashSupport/slides/Mar30_28.html

As for the original rear panel simply squeeze in/out the side tabs a bit, but it up to the "tunnel" and weld it in place, grind down the welds so they look nice and no one will ever question it at tech.

That will give you an extra inch or so of much needed space, out the back, for your sprockets, notice I didn't have to cut a sprocket relief slot like the guys building MTD's do !

[Running on Empty]

Lee,

From the pictures I have seen of your frame, it is a little different.  I  didn't see that your frame had the dropped front end for the engine.  Your frame is straight from the rear axle to the centerline of the front axle.  Am I just missing it in the pics of your mowchine?    I needed to build up the rear a little bit to match the centerline of the front axle to the centerline of the rear axle.  The tunel on this frame is only about 6 inches deep.  Maybe I am going about this all wrong?