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Re: Cushman based build

Posted: Nov 12 2013 11:45am
by johnrobholmes
Yes, it is, Thanks!


Have you done anti-squat calculations on the rear link geometry? Eyeballing it with the ride height in the pics, the axle will want to drive under the rig and chassis roll will be very strong. On sidehills it would make the bed sag on the downhill side and reduce the stability.


It would be prudent to use the vehicle first and see if the chassis roll is noticeable. Your intended use and spring rates may not allow enough articulation to matter. My main concern is chassis roll at speed. You will have more wheelbase change on the outer tires during turns, so oversteering and further chassis roll happens. If you do notice strange behavior or want to improve handling, those upper links will be the place to start. Your upper links should be about parallel with the ground or sloping downward slightly from axle to chassis. Using longer uppers and mounting to the chassis just above the lower link mounts would be the general position for a more neutral anti-squat and roll center.

Re: Cushman based build

Posted: Nov 12 2013 11:59am
by burner1
I think everything is a compromise. I did no computations but basically ran with general design ideas.

The height of the vehicle will be a little lower with the batteries and equipment. I am working with stronger springs now as the initial springs were too weak. I am making my own spring/shock mounts. The rear has a lot of adjustment but the front is fixed so a change in height is a change in new mounts which is not too much trouble.

Springs are pretty stiff. I am running 350lb/inch springs for now.

As far as roll, the 3-wheel Cushman responds well. I only goes about 20mph but with the 3wheeler, stability has never been a problem.

Roll bar on the rear is essential though which you can see under the rear photo.

Re: Cushman based build

Posted: Nov 13 2013 11:26am
by johnrobholmes
I didn't see the sway bar, that will really help a lot. I'm just used to driving trucks without them, so we always put more effort into getting the suspension set up. Between the sway bar and your spring rate I doubt you will have any issues. Love the build, wish I had a need to make such a sweet utility vehicle!

Re: Cushman based build

Posted: Nov 18 2013 2:53pm
by burner1
I am pretty happy with the suspension. It took me a while to get the correct springs and correct load/setup but I think I am there. They will handle the batteries very well and it is far more stable then I expected without the sway bar. I don't think I will need the sway bar. Keep in mind this is not a "Trail-fun" vehicle, this is a work truck for the property and the shop.

What I really like is the bed is big and reasonably low to the ground.


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Re: Cushman based build

Posted: Nov 20 2013 10:00am
by johnrobholmes
Just because it is a work truck doesn't mean you can't have some fun getting through the property at the same time :mrgreen:

That low bed really is a great feature. My wood hauler has the bed 4 feet high, and it really sucks when I can't split logs down small enough to lift so high. On the other hand the truck also has 35" tires and a 6" lift, so it can run through terrain other trucks can't touch. My spring project is a flat bed that will lower it down.

You gonna build rail sides for the bed?

Re: Cushman based build

Posted: Nov 20 2013 10:11am
by burner1
johnrobholmes wrote:Just because it is a work truck doesn't mean you can't have some fun getting through the property at the same time :mrgreen:

That low bed really is a great feature. My wood hauler has the bed 4 feet high, and it really sucks when I can't split logs down small enough to lift so high. On the other hand the truck also has 35" tires and a 6" lift, so it can run through terrain other trucks can't touch. My spring project is a flat bed that will lower it down.

You gonna build rail sides for the bed?
The Cushman low flat bead has been real handy a time or two when I needed to get the rear tractor tire loaded by myself. Saved my bacon.

I am going to do stake bed on the side but I am trying to decide on the details of the how to. I may do a one piece removable aluminum diamond plate...or weld on steel diamond plate sides with a bolt in floor. I really want the floor to be removable.

Re: Cushman based build

Posted: Nov 20 2013 10:21am
by johnrobholmes
Bolt in floor would be pretty sweet for maintenance and cleaning. I'm trying to think of an easy way to make it so the bed is smooth, but the bed removes without getting underneath to unbolt it. Maybe tabs on the side that bolt it into the outer rails? Sectional so it is easy enough to lift out each part? Now you have me thinking about doing something similar on my truck.

Keep us updated, this is my favorite utility vehicle to date!

Re: Cushman based build

Posted: Nov 20 2013 10:26am
by burner1
I'll have good access to the bolts underneath. My thing is I want the strips around the side which I can hook with ratchet straps. If the side is not properly secured the straps could warp the bed. That was my primary reasoning for doing steel sides and an aluminum bed.

Do you have a link to your build?

Re: Cushman based build

Posted: Nov 20 2013 10:33am
by johnrobholmes
My truck is just an old dodge ram with more rust holes than body. Not worth taking up internet space :lol:

Re: Cushman based build

Posted: Nov 20 2013 10:37am
by burner1
Yea it is, lets see a photo of what your doing.

Re: Cushman based build

Posted: Nov 21 2013 6:51pm
by burner1
Welded in the motor/transmission mount, set in the motor, trans and batteries in the car; 12 total. Springs handle the weight perfectly.



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Re: Cushman based build

Posted: Mar 13 2014 5:23pm
by burner1
We have been a little busy, I have not had time to get back to it. I have however came up with an automatic cancel turn signal controller. I even filed a patent on it. The controller controls the turn signals, flashers, brake lights, and even front markers.

The real advantage is they cancel with the inertia in a turn and requires nothing on the steering column:
http://www.gasautosolutions.com/

When I get this finished I am going to set one unit up on this cart.

Re: Cushman based build

Posted: Mar 16 2014 6:42am
by drewjet
Still looking good. I finally removed the transmission on mine and went straight from the motor to the driveshaft. I am still getting bad vibrations above 30 MPH. Some of it I know is coming from the tires not being balanced, because when I remove them the vibrations are less. But I think I also need some more vibration isolation.

Have you run your drivetrane yet?

Re: Cushman based build

Posted: Mar 17 2014 10:21am
by burner1
Not yet,

I need to tie up sheet metal loose ends then get the frame coated. We got some big jobs here in the shop so it is a bit of a back burner.

Are you able to get yours to speed without the motor attached to help isolate where the vibration is coming form?

Re: Cushman based build

Posted: Mar 19 2014 4:28am
by drewjet
With the 3.5:1 ( more or less) rear end reduction, that parking brake disc is spinning at the equivalent speed of 140 MPH wheen I am doing 40 MPH at the wheel.

I think the vibration is coming from the parking brake disc. it is definately not 100% true, more of a wobble than runout, but maybe some vibration is coming from the rear end as well.

I used a vibration Isolator from the transmission on the bottom motor mount, but the top is directly bolted to a frame member. I think I could get some isolation inbetween there if I rework it a bit. But Isoating the vibration is only masking the problem, not fixing it.

I will try and shoot a video to show it.

I would love to just get a whole new rear end with a lower ratio and disc brakes w/ a built in parking brake. I have read that guys are modifying Toyota and GM rear ends to work.

Re: Cushman based build

Posted: Mar 21 2014 8:52pm
by drewjet

Re: Cushman based build

Posted: Mar 22 2014 9:25am
by burner1
Hard to tell; wobble as you say is not necessarily vibration. You could just take it off and take it down to a drive line or engine shop and have it balanced.

I have an MGB that had a vibration and it ended up being that the yoke was not fully engaged on the shaft (or fully pushed on). I lengthened the drive shaft and rebalanced it and vibration gone.

Re: Cushman based build

Posted: Feb 21 2015 11:38am
by burner1
I am still alive and the project is still going. Got busy with other things but it is moving again.

I am trying to get all the panels and small details tied up. I hope in a month or 2 I can get it ready for paint:

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Re: Cushman based build

Posted: Mar 03 2015 5:12pm
by burner1
Finally got some equipment out of the way for a better picture:


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Re: Cushman based build

Posted: Apr 10 2015 2:35pm
by burner1
Under the seat top sets the controller mount in the middle, the emergency brake mount in the back and the shifter for the 2 speed trans toward the front.

Finish up this weekend and off to the blasters to get blasted and primed on Monday.





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Re: Cushman based build

Posted: Apr 11 2015 9:59am
by burner1
A few things done now can really help latter. While I am not finishing dash now, the dash mounts are welded on. I have also welded on a plate for the Automatic Turn Signal and light controller to mount to:


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The dash is in basic form but lots of details to work on it latter. You can also see the tubes welded on the frames should I want to add doors latter:


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Re: Cushman based build

Posted: Apr 13 2015 7:26am
by electron bom
I really like this project, very inspiring. Thanks for sharing!

Re: Cushman based build

Posted: Apr 13 2015 12:22pm
by burner1
Thanks,

As I hauled it off to the blasters, here were a couple of other angles of the suspension and the bumper.



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Re: Cushman based build

Posted: Apr 14 2015 11:30am
by drewjet
Looks awesome!. Looking forward to the final product.

Re: Cushman based build

Posted: Apr 14 2015 12:20pm
by burner1
Thanks Drew, if I can get through the paint process hopefully I can turn the corner.