Air Spade Dimensions


Well-Known Member
The idea is to spend $1860 Canadian for an Airspade 2000 or less than a hundred to build the el cheapo equivilant. Well guess which wins?

Since I am going to build something similar I would like to know what is the inside diameter of the exit nozzle on the homebuilt models out there. I intend on using about 90 PSI at 125 CFM.


Well-Known Member
You are going to need to machine a DeLaval type, converging/diverging nozzle in order to get super/hypersonic air speeds that the air-spad can deliver.

There are very specific calculations involved but doable....look at some of the rocket science web sites.

Also, look up the patent in the USPO for the airspade. They have a great discussion on the methods they used to form the divergent section in order to smooth the airflow and to straighten out the air stream while keeping the speeds supersonic.

$400 usd is a lot of money for a nozzle, but, unless you have access to a machine shop and serious calculus math abilities it seems a whole lot less expensive.

the rest of the tool is pretty much off the shelf components anyway.

BTW I bought some nozzle calculations that will deliver the supersonic speeds you need but will not straigthen the airflow....covers several PSI and CFM choices...Yet I still haven't built my unit yet mainly for lack of a compressor.


Well-Known Member
For now a simple straight hole will do and then a proper nozzle if more work comes up. Once in over a decade will I have a paying customer for the airspade, but there is no way to pay the whole shot off this one job.

The nozzle I have heard is at least $500 Canadian, so it will not be paid by one have day of work and I don't feel like working a different job to pay for something that will lay around.

Tom Dunlap

Here from the beginning
Mike Maas built one a while ago using black iron pipe. Look for him in the member list here or at Treehouse.

Find a valve that will allow you to keep your hand away from the valve body. The valve will get hot from the friction of the air going through.

It took him a while to get the right dimensions for the tip. If I remember correctly he said that the homemade worked OK but the store bought unit paid for itself quite quickly because of increased effeciency.


Well-Known Member
I noticed somebody reading this old thread and thought it worth responding.

I did use a homemade device for a number of years and then bought an Airspade. Still only ocassional work for it but it certainly is a great tool when needed.

For anybody looking at homemade vs. real, buy real if you can, the increased efficiency is well worth the current price of approximately $1200. Also consider the high volume airknife for those that people that will have frequent work and larger jobs.

Root collar excavation is one of the services that can set you apart from the regular tree cutters but you need to do a lot of leg work and have some good customers to be able to make money at it.

In addition to the airspade itself, you will need a large (rental) compressor, tarps and lots of plywood for screening. Cosidering the dirt that is thrown around tyvek overalls are worthwhile.


Well-Known Member
We acquired a Supersonic Airknife three years ago. I also aquired the Air-vac in a really great package deal. I chose the high flow model which can be used in cooperation with a 375cfm compressor.

The 375cfm compressor with the Air-vac is amazing - throwing 3" rocks out the opposing end of 40' of 4" hose.

The 375cfm compressor with the Airknife is frightening and practical in few circumstances. We observed bark/cambium damage to roots. These roots were to be severed anyway as part of a TPZ installation prescription. Interestingly when hooked up to the large compressor the Airknife was able to produce a 25cm long blue flame of high velocity air from the nozzle.

We use the smaller nozzle in cooperation with a 185cfm compressor so often we are considering acquiring our own compressor due to rental costs. Though our favourite rental co. cuts us a very favourable rate in an attempt to discourage us from doing so and to keep our usage frequency up.

A favourite prescription when clients are willing lose turf:
- create and prepare mulch bed around the tree to the dripline extent
- employ Airknife to loosen sod layer
- remove sod
- install 10cm layer of finished compost
- till compost into the soil with airknife
- install 15cm layer of 3 year old, partially composted woodchip mulch

This prescription minus the sod removal - fulfilled June 2011; in cooperation with an irrigation program, MykePro Arbor WP innoculation and 3 applications of compost tea brought 3 of 4 40cm DBH Red Oaks with 70-80% canopy loss (due to transplant with inadequate root balls, dug in Oct 2009, allowed to freeze till March 2010 and installed March 2010)to the point of producing watersprouts this past spring 2012 and increasing the viable canopy to near 50%.

The tree still look like hell, but the increased vigour has made for an elated client.

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